4185

7 files changed, 158 insertions, 102 deletions

diff --git a/subx/011direct_addressing.cc b/subx/011direct_addressing.cc
index 46c24828..2a948626 100644
--- a/subx/011direct_addressing.cc
+++ b/subx/011direct_addressing.cc
@@ -50,6 +50,7 @@ int32_t* effective_address(uint8_t modrm) {
 % Reg[3].i = 1;
 # op  ModR/M  SIB   displacement  immediate
   29  d8                                      # subtract EBX from EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: subtract EBX from effective address
 +run: effective address is EAX
 +run: storing 0x00000009
@@ -71,6 +72,7 @@ case 0x29: {  // subtract r32 from r/m32
 % Reg[3].i = 0x000000ff;
 # op  ModR/M  SIB   displacement  immediate
   21  d8                                      # and EBX with destination EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: and EBX with effective address
 +run: effective address is EAX
 +run: storing 0x0000000d
@@ -92,6 +94,7 @@ case 0x21: {  // and r32 with r/m32
 % Reg[3].i = 0xa0b0c0d0;
 # op  ModR/M  SIB   displacement  immediate
   09  d8                                      # or EBX with destination EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: or EBX with effective address
 +run: effective address is EAX
 +run: storing 0xaabbccdd
@@ -113,6 +116,7 @@ case 0x09: {  // or r32 with r/m32
 % Reg[3].i = 0xaabbc0d0;
 # op  ModR/M  SIB   displacement  immediate
   31  d8                                      # xor EBX with destination EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: xor EBX with effective address
 +run: effective address is EAX
 +run: storing 0xa0b0ccdd
@@ -133,6 +137,7 @@ case 0x31: {  // xor r32 with r/m32
 % Reg[3].i = 0x0f0f00ff;
 # op  ModR/M  SIB   displacement  immediate
   f7  c3                                      # not EBX
+# ModR/M in binary: 11 (direct mode) 000 (unused) 011 (dest EBX)
 +run: 'not' of effective address
 +run: effective address is EBX
 +run: storing 0xf0f0ff00
@@ -155,8 +160,9 @@ case 0xf7: {  // xor r32 with r/m32
 :(scenario compare_r32_with_r32_greater)
 % Reg[0].i = 0x0a0b0c0d;
 % Reg[3].i = 0x0a0b0c07;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   39  d8                                      # compare EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: compare EBX with effective address
 +run: effective address is EAX
 +run: SF=0; ZF=0; OF=0
@@ -180,8 +186,9 @@ case 0x39: {  // set SF if r/m32 < r32
 :(scenario compare_r32_with_r32_lesser)
 % Reg[0].i = 0x0a0b0c07;
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   39  d8                                      # compare EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: compare EBX with effective address
 +run: effective address is EAX
 +run: SF=1; ZF=0; OF=0
@@ -189,8 +196,9 @@ case 0x39: {  // set SF if r/m32 < r32
 :(scenario compare_r32_with_r32_equal)
 % Reg[0].i = 0x0a0b0c0d;
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   39  d8                                      # compare EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: compare EBX with effective address
 +run: effective address is EAX
 +run: SF=0; ZF=1; OF=0
@@ -199,8 +207,9 @@ case 0x39: {  // set SF if r/m32 < r32
 
 :(scenario copy_r32_to_r32)
 % Reg[3].i = 0xaf;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   89  d8                                      # copy EBX to EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: copy EBX to effective address
 +run: effective address is EAX
 +run: storing 0x000000af
@@ -221,8 +230,9 @@ case 0x89: {  // copy r32 to r/m32
 :(scenario xchg_r32_with_r32)
 % Reg[3].i = 0xaf;
 % Reg[0].i = 0x2e;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   87  d8                                      # exchange EBX with EAX
+# ModR/M in binary: 11 (direct mode) 011 (src EBX) 000 (dest EAX)
 +run: exchange EBX with effective address
 +run: effective address is EAX
 +run: storing 0x000000af in effective address
@@ -247,7 +257,7 @@ case 0x87: {  // exchange r32 with r/m32
 :(scenario push_r32)
 % Reg[ESP].u = 0x64;
 % Reg[EBX].i = 0x0000000a;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   53                                          # push EBX to stack
 +run: push EBX
 +run: decrementing ESP to 0x00000060
@@ -280,7 +290,7 @@ void push(uint32_t val) {
 :(scenario pop_r32)
 % Reg[ESP].u = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0000000a);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   5b                                          # pop stack to EBX
 +run: pop into EBX
 +run: popping value 0x0000000a
diff --git a/subx/012indirect_addressing.cc b/subx/012indirect_addressing.cc
index f41bdfef..ca6843d4 100644
--- a/subx/012indirect_addressing.cc
+++ b/subx/012indirect_addressing.cc
@@ -6,15 +6,15 @@
 % SET_WORD_IN_MEM(0x60, 1);
 # op  ModR/M  SIB   displacement  immediate
   01  18                                     # add EBX to *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: add EBX to effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x00000011
 
 :(before "End Mod Special-cases")
 case 0:
-  // mod 0 is usually indirect addressing
   switch (rm) {
-  default:
+  default:  // mod 0 is usually indirect addressing
     trace(2, "run") << "effective address is mem at address 0x" << std::hex << Reg[rm].u << " (" << rname(rm) << ")" << end();
     assert(Reg[rm].u + sizeof(int32_t) <= Mem.size());
     result = reinterpret_cast<int32_t*>(&Mem.at(Reg[rm].u));  // rely on the host itself being in little-endian order
@@ -31,6 +31,7 @@ case 0:
 % SET_WORD_IN_MEM(0x60, 1);
 # op  ModR/M  SIB   displacement  immediate
   03  18                                      # add *EAX to EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: add effective address to EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x00000011
@@ -51,8 +52,9 @@ case 0x03: {  // add r/m32 to r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 10);
 % Reg[3].i = 1;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   29  18                                      # subtract EBX from *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: subtract EBX from effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x00000009
@@ -63,8 +65,9 @@ case 0x03: {  // add r/m32 to r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 1);
 % Reg[3].i = 10;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   2b  18                                      # subtract *EAX from EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: subtract effective address from EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x00000009
@@ -85,8 +88,9 @@ case 0x2b: {  // subtract r/m32 from r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0xff;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   21  18                                      # and EBX with *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: and EBX with effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x0000000d
@@ -97,8 +101,9 @@ case 0x2b: {  // subtract r/m32 from r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x000000ff);
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   23  18                                      # and *EAX with EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: and effective address with EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x0000000d
@@ -119,8 +124,9 @@ case 0x23: {  // and r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0xa0b0c0d0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   09  18                                      # or EBX with *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: or EBX with effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0xaabbccdd
@@ -131,8 +137,9 @@ case 0x23: {  // and r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0xa0b0c0d0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   0b  18                                      # or *EAX with EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: or effective address with EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0xaabbccdd
@@ -153,8 +160,9 @@ case 0x0b: {  // or r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0xaabb0c0d);
 % Reg[3].i = 0xa0b0c0d0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   31  18                                      # xor EBX with *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: xor EBX with effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x0a0bccdd
@@ -165,8 +173,9 @@ case 0x0b: {  // or r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0xa0b0c0d0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   33  18                                      # xor *EAX with EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: xor effective address with EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0xaabbccdd
@@ -187,8 +196,9 @@ case 0x33: {  // xor r/m32 with r32
 % Reg[3].i = 0x60;
 # word at 0x60 is 0x0f0f00ff
 % SET_WORD_IN_MEM(0x60, 0x0f0f00ff);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   f7  03                                      # negate *EBX
+# ModR/M in binary: 00 (indirect mode) 000 (unused) 011 (dest EBX)
 +run: 'not' of effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: storing 0xf0f0ff00
@@ -199,8 +209,9 @@ case 0x33: {  // xor r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0x0a0b0c07;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   39  18                                      # compare EBX with *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: compare EBX with effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: SF=0; ZF=0; OF=0
@@ -209,8 +220,9 @@ case 0x33: {  // xor r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c07);
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   39  18                                      # compare EBX with *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: compare EBX with effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: SF=1; ZF=0; OF=0
@@ -219,8 +231,9 @@ case 0x33: {  // xor r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   39  18                                      # compare EBX with *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: compare EBX with effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: SF=0; ZF=1; OF=0
@@ -231,8 +244,9 @@ case 0x33: {  // xor r/m32 with r32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c07);
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   3b  18                                      # compare *EAX with EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: compare effective address with EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: SF=0; ZF=0; OF=0
@@ -257,8 +271,9 @@ case 0x3b: {  // set SF if r32 < r/m32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0x0a0b0c07;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   3b  18                                      # compare *EAX with EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: compare effective address with EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: SF=1; ZF=0; OF=0
@@ -267,8 +282,9 @@ case 0x3b: {  // set SF if r32 < r/m32
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0a0b0c0d);
 % Reg[3].i = 0x0a0b0c0d;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   3b  18                                      # compare *EAX with EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: compare effective address with EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: SF=0; ZF=1; OF=0
@@ -278,8 +294,9 @@ case 0x3b: {  // set SF if r32 < r/m32
 :(scenario copy_r32_to_mem_at_r32)
 % Reg[3].i = 0xaf;
 % Reg[0].i = 0x60;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   89  18                                      # copy EBX to *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: copy EBX to effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x000000af
@@ -289,8 +306,9 @@ case 0x3b: {  // set SF if r32 < r/m32
 :(scenario copy_mem_at_r32_to_r32)
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x000000af);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   8b  18                                      # copy *EAX to EBX
+# ModR/M in binary: 00 (indirect mode) 011 (src EAX) 000 (dest EAX)
 +run: copy effective address to EBX
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x000000af
@@ -311,8 +329,9 @@ case 0x8b: {  // copy r32 to r/m32
 :(scenario jump_mem_at_r32)
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 8);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   ff  20                                      # jump to *EAX
+# ModR/M in binary: 00 (indirect mode) 100 (jump to r/m32) 000 (src EAX)
   05                              00 00 00 01
   05                              00 00 00 02
 +run: inst: 0x00000001
@@ -345,8 +364,9 @@ case 0xff: {
 % Reg[0].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x000000af);
 % Reg[ESP].u = 0x14;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   ff  30                                      # push *EAX to stack
+# ModR/M in binary: 00 (indirect mode) 110 (push r/m32) 000 (src EAX)
 +run: push effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: decrementing ESP to 0x00000010
@@ -366,8 +386,9 @@ case 6: {  // push r/m32 to stack
 % Reg[0].i = 0x60;
 % Reg[ESP].u = 0x10;
 % SET_WORD_IN_MEM(0x10, 0x00000030);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   8f  00                                      # pop stack into *EAX
+# ModR/M in binary: 00 (indirect mode) 000 (pop r/m32) 000 (dest EAX)
 +run: pop into effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: popping value 0x00000030
diff --git a/subx/013immediate_addressing.cc b/subx/013immediate_addressing.cc
index 3021617f..14099fee 100644
--- a/subx/013immediate_addressing.cc
+++ b/subx/013immediate_addressing.cc
@@ -2,8 +2,9 @@
 
 :(scenario add_imm32_to_r32)
 % Reg[3].i = 1;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  c3                          0a 0b 0c 0d  # add 0x0d0c0b0a to EBX
+# ModR/M in binary: 11 (direct mode) 000 (add imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is EBX
 +run: subop add
@@ -36,6 +37,7 @@ case 0x81: {  // combine imm32 with r/m32
 % SET_WORD_IN_MEM(0x60, 1);
 # op  ModR/M  SIB   displacement  immediate
   81  03                          0a 0b 0c 0d  # add 0x0d0c0b0a to *EBX
+# ModR/M in binary: 00 (indirect mode) 000 (add imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: subop add
@@ -63,31 +65,33 @@ case 0x2d: {  // subtract imm32 from EAX
 :(scenario subtract_imm32_from_mem_at_r32)
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 10);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  2b                          01 00 00 00  # subtract 1 from *EBX
+# ModR/M in binary: 00 (indirect mode) 101 (subtract imm32) 011 (dest EBX)
 +run: combine imm32 0x00000001 with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: subop subtract
 +run: storing 0x00000009
 
+:(before "End Op 81 Subops")
+case 5: {
+  trace(2, "run") << "subop subtract" << end();
+  BINARY_ARITHMETIC_OP(-, *arg1, arg2);
+  break;
+}
+
 //:
 
 :(scenario subtract_imm32_from_r32)
 % Reg[3].i = 10;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  eb                          01 00 00 00  # subtract 1 from EBX
+# ModR/M in binary: 11 (direct mode) 101 (subtract imm32) 011 (dest EBX)
 +run: combine imm32 0x00000001 with effective address
 +run: effective address is EBX
 +run: subop subtract
 +run: storing 0x00000009
 
-:(before "End Op 81 Subops")
-case 5: {
-  trace(2, "run") << "subop subtract" << end();
-  BINARY_ARITHMETIC_OP(-, *arg1, arg2);
-  break;
-}
-
 //:: and
 
 :(scenario and_imm32_with_eax)
@@ -110,31 +114,33 @@ case 0x25: {  // and imm32 with EAX
 :(scenario and_imm32_with_mem_at_r32)
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x000000ff);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  23                          0a 0b 0c 0d  # and 0x0d0c0b0a with *EBX
+# ModR/M in binary: 00 (indirect mode) 100 (and imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: subop and
 +run: storing 0x0000000a
 
+:(before "End Op 81 Subops")
+case 4: {
+  trace(2, "run") << "subop and" << end();
+  BINARY_BITWISE_OP(&, *arg1, arg2);
+  break;
+}
+
 //:
 
 :(scenario and_imm32_with_r32)
 % Reg[3].i = 0xff;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  e3                          0a 0b 0c 0d  # and 0x0d0c0b0a with EBX
+# ModR/M in binary: 11 (direct mode) 100 (and imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is EBX
 +run: subop and
 +run: storing 0x0000000a
 
-:(before "End Op 81 Subops")
-case 4: {
-  trace(2, "run") << "subop and" << end();
-  BINARY_BITWISE_OP(&, *arg1, arg2);
-  break;
-}
-
 //:: or
 
 :(scenario or_imm32_with_eax)
@@ -157,8 +163,9 @@ case 0x0d: {  // or imm32 with EAX
 :(scenario or_imm32_with_mem_at_r32)
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0xd0c0b0a0);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  0b                          0a 0b 0c 0d  # or 0x0d0c0b0a with *EBX
+# ModR/M in binary: 00 (indirect mode) 001 (or imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: subop or
@@ -173,8 +180,9 @@ case 1: {
 
 :(scenario or_imm32_with_r32)
 % Reg[3].i = 0xd0c0b0a0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  cb                          0a 0b 0c 0d  # or 0x0d0c0b0a with EBX
+# ModR/M in binary: 11 (direct mode) 001 (or imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is EBX
 +run: subop or
@@ -202,8 +210,9 @@ case 0x35: {  // xor imm32 with EAX
 :(scenario xor_imm32_with_mem_at_r32)
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0xd0c0b0a0);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  33                          0a 0b 0c 0d  # xor 0x0d0c0b0a with *EBX
+# ModR/M in binary: 00 (indirect mode) 110 (xor imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: subop xor
@@ -218,8 +227,9 @@ case 6: {
 
 :(scenario xor_imm32_with_r32)
 % Reg[3].i = 0xd0c0b0a0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  f3                          0a 0b 0c 0d  # xor 0x0d0c0b0a with EBX
+# ModR/M in binary: 11 (direct mode) 110 (xor imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is EBX
 +run: subop xor
@@ -229,7 +239,7 @@ case 6: {
 
 :(scenario compare_imm32_with_eax_greater)
 % Reg[0].i = 0x0d0c0b0a;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   3d                              07 0b 0c 0d  # compare 0x0d0c0b07 with EAX
 +run: compare EAX and imm32 0x0d0c0b07
 +run: SF=0; ZF=0; OF=0
@@ -250,14 +260,14 @@ case 0x3d: {  // subtract imm32 from EAX
 
 :(scenario compare_imm32_with_eax_lesser)
 % Reg[0].i = 0x0d0c0b07;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   3d                              0a 0b 0c 0d  # compare 0x0d0c0b0a with EAX
 +run: compare EAX and imm32 0x0d0c0b0a
 +run: SF=1; ZF=0; OF=0
 
 :(scenario compare_imm32_with_eax_equal)
 % Reg[0].i = 0x0d0c0b0a;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   3d                              0a 0b 0c 0d  # compare 0x0d0c0b0a with EAX
 +run: compare EAX and imm32 0x0d0c0b0a
 +run: SF=0; ZF=1; OF=0
@@ -266,8 +276,9 @@ case 0x3d: {  // subtract imm32 from EAX
 
 :(scenario compare_imm32_with_r32_greater)
 % Reg[3].i = 0x0d0c0b0a;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  fb                          07 0b 0c 0d  # compare 0x0d0c0b07 with EBX
+# ModR/M in binary: 11 (direct mode) 111 (compare imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b07 with effective address
 +run: effective address is EBX
 +run: SF=0; ZF=0; OF=0
@@ -286,16 +297,20 @@ case 7: {
 
 :(scenario compare_imm32_with_r32_lesser)
 % Reg[3].i = 0x0d0c0b07;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  fb                          0a 0b 0c 0d  # compare 0x0d0c0b0a with EBX
+# ModR/M in binary: 11 (direct mode) 111 (compare imm32) 011 (dest EBX)
++run: combine imm32 0x0d0c0b07 with effective address
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is EBX
 +run: SF=1; ZF=0; OF=0
 
 :(scenario compare_imm32_with_r32_equal)
 % Reg[3].i = 0x0d0c0b0a;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  fb                          0a 0b 0c 0d  # compare 0x0d0c0b0a with EBX
+# ModR/M in binary: 11 (direct mode) 111 (compare imm32) 011 (dest EBX)
++run: combine imm32 0x0d0c0b07 with effective address
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is EBX
 +run: SF=0; ZF=1; OF=0
@@ -303,8 +318,10 @@ case 7: {
 :(scenario compare_imm32_with_mem_at_r32_greater)
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0d0c0b0a);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  3b                          07 0b 0c 0d  # compare 0x0d0c0b07 with *EBX
+# ModR/M in binary: 00 (indirect mode) 111 (compare imm32) 011 (dest EBX)
++run: combine imm32 0x0d0c0b07 with effective address
 +run: combine imm32 0x0d0c0b07 with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: SF=0; ZF=0; OF=0
@@ -312,8 +329,9 @@ case 7: {
 :(scenario compare_imm32_with_mem_at_r32_lesser)
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0d0c0b07);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  3b                          0a 0b 0c 0d  # compare 0x0d0c0b0a with *EBX
+# ModR/M in binary: 00 (indirect mode) 111 (compare imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: SF=1; ZF=0; OF=0
@@ -322,8 +340,9 @@ case 7: {
 % Reg[3].i = 0x0d0c0b0a;
 % Reg[3].i = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x0d0c0b0a);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   81  3b                          0a 0b 0c 0d  # compare 0x0d0c0b0a with *EBX
+# ModR/M in binary: 00 (indirect mode) 111 (compare imm32) 011 (dest EBX)
 +run: combine imm32 0x0d0c0b0a with effective address
 +run: effective address is mem at address 0x60 (EBX)
 +run: SF=0; ZF=1; OF=0
@@ -331,7 +350,7 @@ case 7: {
 //:: copy (mov)
 
 :(scenario copy_imm32_to_r32)
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   bb                              0a 0b 0c 0d  # copy 0x0d0c0b0a to EBX
 +run: copy imm32 0x0d0c0b0a to EBX
 
@@ -355,8 +374,9 @@ case 0xbf: {  // copy imm32 to r32
 
 :(scenario copy_imm32_to_mem_at_r32)
 % Reg[3].i = 0x60;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   c7  03                          0a 0b 0c 0d  # copy 0x0d0c0b0a to *EBX
+# ModR/M in binary: 00 (indirect mode) 000 (unused) 011 (dest EBX)
 +run: copy imm32 0x0d0c0b0a to effective address
 +run: effective address is mem at address 0x60 (EBX)
 
@@ -374,7 +394,7 @@ case 0xc7: {  // copy imm32 to r32
 
 :(scenario push_imm32)
 % Reg[ESP].u = 0x14;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   68                              af 00 00 00  # push *EAX to stack
 +run: push imm32 0x000000af
 +run: ESP is now 0x00000010
diff --git a/subx/014index_addressing.cc b/subx/014index_addressing.cc
index 389808d1..4deff72a 100644
--- a/subx/014index_addressing.cc
+++ b/subx/014index_addressing.cc
@@ -6,22 +6,27 @@
 % SET_WORD_IN_MEM(0x60, 1);
 # op  ModR/M  SIB   displacement  immediate
   01  1c      20                             # add EBX to *EAX
+# ModR/M in binary: 00 (indirect mode) 011 (src EBX) 000 (dest EAX)
 # SIB in binary: 00 (scale 1) 100 (no index) 000 (base EAX)
-# See Table 2-3 of the Intel programming manual.
 +run: add EBX to effective address
 +run: effective address is mem at address 0x60 (EAX)
 +run: storing 0x00000011
 
 :(before "End Mod 0 Special-cases")
-case 4:
-  // exception: SIB addressing
+case 4:  // exception: mod 0b00 rm 0b100 => incoming SIB (scale-index-base) byte
   uint8_t sib = next();
   uint8_t base = sib&0x7;
   if (base == EBP) {
-    // This gets complicated. In the example below, do the two disp8's accumulate? multiply? cancel out?!
+    // Need to sometimes use a displacement either in addition to or in place
+    // of EBP. This gets complicated, and I don't understand interactions with
+    // displacement mode in Mod/RM. For example:
+    //
     // op (hex)   ModR/M (binary)                     SIB (binary)                                      displacement (hex)
     // 0x01       01 100 /*SIB+disp8*/ 000 /*EAX*/    00 /*scale*/ 100 /*no index*/ 101 /*EBP+disp8*/   0xf0
     //
+    // Do the two disp8's accumulate (so the instruction has *two* disp8's)?
+    // multiply? cancel out?!
+    //
     // Maybe this is the answer:
     //   "When the ModR/M or SIB tables state that a disp value is required..
     //   then the displacement bytes are required."
@@ -43,15 +48,15 @@ case 4:
   }
   break;
 
-:(scenario add_r32_to_mem_at_base_plus_index)
+:(scenario add_r32_to_mem_at_base_r32_index_r32)
 % Reg[3].i = 0x10;  // source
 % Reg[0].i = 0x5e;  // dest base
 % Reg[1].i = 0x2;  // dest index
 % SET_WORD_IN_MEM(0x60, 1);
 # op  ModR/M  SIB   displacement  immediate
   01  1c      08                             # add EBX to *(EAX+ECX)
+# ModR/M in binary: 00 (indirect mode) 011 (src EBX) 000 (dest EAX)
 # SIB in binary: 00 (scale 1) 001 (index ECX) 000 (base EAX)
-# See Table 2-3 of the Intel programming manual.
 +run: add EBX to effective address
 +run: effective address is mem at address 0x60 (EAX + ECX*1)
 +run: storing 0x00000011
diff --git a/subx/015jump_relative.cc b/subx/015jump_relative.cc
index c9cdcd1b..2d3bbb2b 100644
--- a/subx/015jump_relative.cc
+++ b/subx/015jump_relative.cc
@@ -3,7 +3,7 @@
 //:: jump
 
 :(scenario jump_rel8)
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   eb                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -24,7 +24,7 @@ case 0xeb: {  // jump rel8
 
 :(scenario je_rel8_success)
 % ZF = true;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   74                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -45,7 +45,7 @@ case 0x74: {  // jump rel8 if ZF
 
 :(scenario je_rel8_fail)
 % ZF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   74                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -58,7 +58,7 @@ case 0x74: {  // jump rel8 if ZF
 
 :(scenario jne_rel8_success)
 % ZF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   75                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -79,7 +79,7 @@ case 0x75: {  // jump rel8 unless ZF
 
 :(scenario jne_rel8_fail)
 % ZF = true;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   75                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -94,7 +94,7 @@ case 0x75: {  // jump rel8 unless ZF
 % ZF = false;
 % SF = false;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7f                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -117,7 +117,7 @@ case 0x7f: {  // jump rel8 if !SF and !ZF
 % ZF = false;
 % SF = true;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7f                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -131,7 +131,7 @@ case 0x7f: {  // jump rel8 if !SF and !ZF
 :(scenario jge_rel8_success)
 % SF = false;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7d                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -153,7 +153,7 @@ case 0x7d: {  // jump rel8 if !SF
 :(scenario jge_rel8_fail)
 % SF = true;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7d                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -168,7 +168,7 @@ case 0x7d: {  // jump rel8 if !SF
 % ZF = false;
 % SF = true;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7c                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -191,7 +191,7 @@ case 0x7c: {  // jump rel8 if SF and !ZF
 % ZF = false;
 % SF = false;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7c                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -206,7 +206,7 @@ case 0x7c: {  // jump rel8 if SF and !ZF
 % ZF = true;
 % SF = false;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7e                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -219,7 +219,7 @@ case 0x7c: {  // jump rel8 if SF and !ZF
 % ZF = false;
 % SF = true;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7e                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -242,7 +242,7 @@ case 0x7e: {  // jump rel8 if SF or ZF
 % ZF = false;
 % SF = false;
 % OF = false;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   7e                05                        # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
diff --git a/subx/016jump_relative.cc b/subx/016jump_relative.cc
index c4d92030..8b8452bb 100644
--- a/subx/016jump_relative.cc
+++ b/subx/016jump_relative.cc
@@ -3,7 +3,7 @@
 //:: jump
 
 :(scenario jump_rel16)
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   e9                05 00                     # skip 1 instruction
   05                              00 00 00 01
   05                              00 00 00 02
@@ -30,7 +30,7 @@ int16_t imm16() {
 
 :(scenario je_rel16_success)
 % ZF = true;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 84                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -51,7 +51,7 @@ case 0x84: {  // jump rel16 if ZF
 
 :(scenario je_rel16_fail)
 % ZF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 84                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -64,7 +64,7 @@ case 0x84: {  // jump rel16 if ZF
 
 :(scenario jne_rel16_success)
 % ZF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 85                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -85,7 +85,7 @@ case 0x85: {  // jump rel16 unless ZF
 
 :(scenario jne_rel16_fail)
 % ZF = true;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 85                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -100,7 +100,7 @@ case 0x85: {  // jump rel16 unless ZF
 % ZF = false;
 % SF = false;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8f                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -123,7 +123,7 @@ case 0x8f: {  // jump rel16 if !SF and !ZF
 % ZF = false;
 % SF = true;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8f                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -137,7 +137,7 @@ case 0x8f: {  // jump rel16 if !SF and !ZF
 :(scenario jge_rel16_success)
 % SF = false;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8d                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -159,7 +159,7 @@ case 0x8d: {  // jump rel16 if !SF
 :(scenario jge_rel16_fail)
 % SF = true;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8d                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -174,7 +174,7 @@ case 0x8d: {  // jump rel16 if !SF
 % ZF = false;
 % SF = true;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8c                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -197,7 +197,7 @@ case 0x8c: {  // jump rel16 if SF and !ZF
 % ZF = false;
 % SF = false;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8c                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -212,7 +212,7 @@ case 0x8c: {  // jump rel16 if SF and !ZF
 % ZF = true;
 % SF = false;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8e                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -225,7 +225,7 @@ case 0x8c: {  // jump rel16 if SF and !ZF
 % ZF = false;
 % SF = true;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8e                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
@@ -248,7 +248,7 @@ case 0x8e: {  // jump rel16 if SF or ZF
 % ZF = false;
 % SF = false;
 % OF = false;
-# op      ModRM   SIB   displacement  immediate
+# op      ModR/M  SIB   displacement  immediate
   0f 8e                 05 00                     # skip 1 instruction
   05                                  00 00 00 01
   05                                  00 00 00 02
diff --git a/subx/017functions.cc b/subx/017functions.cc
index 774bbf42..cee11fc0 100644
--- a/subx/017functions.cc
+++ b/subx/017functions.cc
@@ -2,7 +2,7 @@
 
 :(scenario call_imm32)
 % Reg[ESP].u = 0x64;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   e8                              a0 00 00 00  # call function offset at 0x000000a0
   # next EIP is 6
 +run: call imm32 0x000000a0
@@ -25,7 +25,7 @@ case 0xe8: {  // call imm32 relative to next EIP
 :(scenario call_r32)
 % Reg[ESP].u = 0x64;
 % Reg[EBX].u = 0x000000a0;
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   ff  d3                                       # call function offset at EBX
   # next EIP is 3
 +run: call to effective address
@@ -48,7 +48,7 @@ case 2: {  // call function pointer at r/m32
 % Reg[ESP].u = 0x64;
 % Reg[EBX].u = 0x10;
 % SET_WORD_IN_MEM(0x10, 0x000000a0);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   ff  13                                       # call function offset at *EBX
   # next EIP is 3
 +run: call to effective address
@@ -62,7 +62,7 @@ case 2: {  // call function pointer at r/m32
 :(scenario ret)
 % Reg[ESP].u = 0x60;
 % SET_WORD_IN_MEM(0x60, 0x00000010);
-# op  ModRM   SIB   displacement  immediate
+# op  ModR/M  SIB   displacement  immediate
   c3
 +run: return
 +run: popping value 0x00000010