4049

Instead of organizing layers by instruction, do so by addressing mode.

1 files changed, 89 insertions, 0 deletions

diff --git a/subx/013immediate_addressing.cc b/subx/013immediate_addressing.cc
new file mode 100644
index 00000000..25a362c2
--- /dev/null
+++ b/subx/013immediate_addressing.cc
@@ -0,0 +1,89 @@
+//: instructions that (immediately) contain an argument to act with
+
+:(scenario add_imm32_to_r32)
+% Reg[3].i = 1;
+# op  ModRM   SIB   displacement  immediate
+  81  c3                          0a 0b 0c 0d  # add 0x0d0c0b0a to EBX (reg 3)
++run: combine imm32 0x0d0c0b0a with effective address
++run: effective address is reg 3
++run: subop add
++run: storing 0x0d0c0b0b
+
+:(before "End Single-Byte Opcodes")
+case 0x81: {  // combine imm32 with r/m32
+  uint8_t modrm = next();
+  int32_t arg2 = imm32();
+  trace(2, "run") << "combine imm32 0x" << HEXWORD << arg2 << " with effective address" << end();
+  int32_t* arg1 = effective_address(modrm);
+  uint8_t subop = (modrm>>3)&0x7;  // middle 3 'reg opcode' bits
+  switch (subop) {
+  case 0:
+    trace(2, "run") << "subop add" << end();
+    BINARY_ARITHMETIC_OP(+, *arg1, arg2);
+    break;
+  // End Op 81 Subops
+  default:
+    cerr << "unrecognized sub-opcode after 81: " << NUM(subop) << '\n';
+    exit(1);
+  }
+  break;
+}
+
+//:
+
+:(scenario add_imm32_to_mem_at_r32)
+% Reg[3].i = 0x60;
+% Mem.at(0x60) = 1;
+# op  ModR/M  SIB   displacement  immediate
+  81  03                          0a 0b 0c 0d  # add 0x0d0c0b0a to *EBX (reg 3)
++run: combine imm32 0x0d0c0b0a with effective address
++run: effective address is mem at address 0x60 (reg 3)
++run: subop add
++run: storing 0x0d0c0b0b
+
+//:: subtract
+
+:(scenario sub_imm32_from_eax)
+% Reg[EAX].i = 0x0d0c0baa;
+# op  ModR/M  SIB   displacement  immediate
+  2d                              0a 0b 0c 0d  # subtract 0x0d0c0b0a from EAX (reg 0)
++run: subtract imm32 0x0d0c0b0a from reg EAX
++run: storing 0x000000a0
+
+:(before "End Single-Byte Opcodes")
+case 0x2d: {  // subtract imm32 from EAX
+  int32_t arg2 = imm32();
+  trace(2, "run") << "subtract imm32 0x" << HEXWORD << arg2 << " from reg EAX" << end();
+  BINARY_ARITHMETIC_OP(-, Reg[EAX].i, arg2);
+  break;
+}
+
+//:
+
+:(scenario sub_imm32_from_mem_at_r32)
+% Reg[3].i = 0x60;
+% Mem.at(0x60) = 10;
+# op  ModRM   SIB   displacement  immediate
+  81  2b                          01 00 00 00  # subtract 1 from *EBX (reg 3)
++run: combine imm32 0x00000001 with effective address
++run: effective address is mem at address 0x60 (reg 3)
++run: subop subtract
++run: storing 0x00000009
+
+//:
+
+:(scenario sub_imm32_from_r32)
+% Reg[3].i = 10;
+# op  ModRM   SIB   displacement  immediate
+  81  eb                          01 00 00 00  # subtract 1 from EBX (reg 3)
++run: combine imm32 0x00000001 with effective address
++run: effective address is reg 3
++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;
+}