From 8a0268317fbce2baa2e5119c796750ea6c80a813 Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Wed, 18 Oct 2017 02:27:56 -0700
Subject: 4084

subx: extract helpers for 'push' and 'pop'. We will be using them in
'call' and 'ret' as well.
---
 subx/011direct_addressing.cc   | 30 ++++++++++++++++++------------
 subx/012indirect_addressing.cc | 19 ++++++-------------
 2 files changed, 24 insertions(+), 25 deletions(-)

(limited to 'subx')

diff --git a/subx/011direct_addressing.cc b/subx/011direct_addressing.cc
index b3f234b3..9e5f6e80 100644
--- a/subx/011direct_addressing.cc
+++ b/subx/011direct_addressing.cc
@@ -223,9 +223,8 @@ case 0x89: {  // copy r32 to r/m32
 # op  ModRM   SIB   displacement  immediate
   53                                          # push EBX (reg 3) to stack
 +run: push reg 3
++run: decrementing ESP to 0x00000060
 +run: pushing value 0x0000000a
-+run: ESP is now 0x00000060
-+run: contents at ESP: 0x0000000a
 
 :(before "End Single-Byte Opcodes")
 case 0x50:
@@ -238,13 +237,15 @@ case 0x56:
 case 0x57: {  // push r32 to stack
   uint8_t reg = op & 0x7;
   trace(2, "run") << "push reg " << NUM(reg) << end();
-  const int32_t val = Reg[reg].u;
-  trace(2, "run") << "pushing value 0x" << HEXWORD << val << end();
+  push(Reg[reg].u);
+  break;
+}
+:(code)
+void push(uint32_t val) {
   Reg[ESP].u -= 4;
+  trace(2, "run") << "decrementing ESP to 0x" << HEXWORD << Reg[ESP].u << end();
+  trace(2, "run") << "pushing value 0x" << HEXWORD << val << end();
   *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u)) = val;
-  trace(2, "run") << "ESP is now 0x" << HEXWORD << Reg[ESP].u << end();
-  trace(2, "run") << "contents at ESP: 0x" << HEXWORD << *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u)) << end();
-  break;
 }
 
 //:: pop
@@ -256,7 +257,7 @@ case 0x57: {  // push r32 to stack
   5b                                          # pop stack to EBX (reg 3)
 +run: pop into reg 3
 +run: popping value 0x0000000a
-+run: ESP is now 0x00000064
++run: incrementing ESP to 0x00000064
 
 :(before "End Single-Byte Opcodes")
 case 0x58:
@@ -269,9 +270,14 @@ case 0x5e:
 case 0x5f: {  // pop stack into r32
   uint8_t reg = op & 0x7;
   trace(2, "run") << "pop into reg " << NUM(reg) << end();
-  Reg[reg].u = *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u));
-  trace(2, "run") << "popping value 0x" << HEXWORD << Reg[reg].u << end();
-  Reg[ESP].u += 4;
-  trace(2, "run") << "ESP is now 0x" << HEXWORD << Reg[ESP].u << end();
+  Reg[reg].u = pop();
   break;
 }
+:(code)
+uint32_t pop() {
+  uint32_t result = *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u));
+  trace(2, "run") << "popping value 0x" << HEXWORD << result << end();
+  Reg[ESP].u += 4;
+  trace(2, "run") << "incrementing ESP to 0x" << HEXWORD << Reg[ESP].u << end();
+  return result;
+}
diff --git a/subx/012indirect_addressing.cc b/subx/012indirect_addressing.cc
index 37d82a3f..f4e8c665 100644
--- a/subx/012indirect_addressing.cc
+++ b/subx/012indirect_addressing.cc
@@ -349,18 +349,14 @@ case 0xff: {  // jump to r/m32
   ff  30                                      # push *EAX (reg 0) to stack
 +run: push effective address
 +run: effective address is mem at address 0x60 (reg 0)
-+run: ESP is now 0x00000010
-+run: contents at ESP: 0x000000af
++run: decrementing ESP to 0x00000010
++run: pushing value 0x000000af
 
 :(before "End Op ff Subops")
 case 6: {
   trace(2, "run") << "push effective address" << end();
   const int32_t* val = effective_address(modrm);
-  trace(2, "run") << "pushing value 0x" << HEXWORD << *val << end();
-  Reg[ESP].u -= 4;
-  *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u)) = *val;
-  trace(2, "run") << "ESP is now 0x" << HEXWORD << Reg[ESP].u << end();
-  trace(2, "run") << "contents at ESP: 0x" << HEXWORD << *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u)) << end();
+  push(*val);
   break;
 }
 
@@ -374,8 +370,8 @@ case 6: {
   8f  00                                      # pop stack into *EAX (reg 0)
 +run: pop into effective address
 +run: effective address is mem at address 0x60 (reg 0)
-+run: storing 0x00000030
-+run: ESP is now 0x00000014
++run: popping value 0x00000030
++run: incrementing ESP to 0x00000014
 
 :(before "End Single-Byte Opcodes")
 case 0x8f: {  // pop stack into r/m32
@@ -385,10 +381,7 @@ case 0x8f: {  // pop stack into r/m32
     case 0: {
       trace(2, "run") << "pop into effective address" << end();
       int32_t* dest = effective_address(modrm);
-      *dest = *reinterpret_cast<uint32_t*>(&Mem.at(Reg[ESP].u));
-      trace(2, "run") << "storing 0x" << HEXWORD << *dest << end();
-      Reg[ESP].u += 4;
-      trace(2, "run") << "ESP is now 0x" << HEXWORD << Reg[ESP].u << end();
+      *dest = pop();
       break;
     }
   }
-- 
cgit 1.4.1-2-gfad0