From 49a4e0971952248c66ee8bbb2a92a8f1a0a6d5ab Mon Sep 17 00:00:00 2001
From: Sintendo <bram.speeckaert@gmail.com>
Date: Wed, 29 Jan 2020 23:01:57 +0100
Subject: [PATCH] DSPJit: Replace/optimize LEAs

- LEA is a bit silly when the source and the destination are the same. A
simple ADD or SHL will do in those cases.

66 8D 04 45 00 00 00 00 lea         ax,[rax*2]
66 03 C0                add         ax,ax

48 8D 04 00             lea         rax,[rax+rax]
48 03 C0                add         rax,rax

66 8D 14 D5 00 00 00 00 lea         dx,[rdx*8]
66 C1 E2 03             shl         dx,3

- When scaling by 2, consider summing the register with itself instead.
The former always needs a 32-bit displacement, so the sum is more
compact.

66 8D 14 45 00 00 00 00 lea dx,[rax*2]
66 8D 14 00             lea dx,[rax+rax]
---
 Source/Core/Core/DSP/Jit/x64/DSPJitBranch.cpp     | 6 +++---
 Source/Core/Core/DSP/Jit/x64/DSPJitMultiplier.cpp | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/Source/Core/Core/DSP/Jit/x64/DSPJitBranch.cpp b/Source/Core/Core/DSP/Jit/x64/DSPJitBranch.cpp
index e08a6ac57e..339d81b4e3 100644
--- a/Source/Core/Core/DSP/Jit/x64/DSPJitBranch.cpp
+++ b/Source/Core/Core/DSP/Jit/x64/DSPJitBranch.cpp
@@ -38,7 +38,7 @@ void DSPEmitter::ReJitConditional(const UDSPInstruction opc,
   case 0x3:  // LE - Less Equal
     LEA(16, EDX, MScaled(EAX, SCALE_4, 0));
     XOR(16, R(EAX), R(EDX));
-    LEA(16, EAX, MScaled(EAX, SCALE_2, 0));
+    ADD(16, R(EAX), R(EAX));
     OR(16, R(EAX), R(EDX));
     TEST(16, R(EAX), Imm16(0x10));
     break;
@@ -56,9 +56,9 @@ void DSPEmitter::ReJitConditional(const UDSPInstruction opc,
     break;
   case 0xa:  // ?
   case 0xb:  // ?
-    LEA(16, EDX, MScaled(EAX, SCALE_2, 0));
+    LEA(16, EDX, MRegSum(EAX, EAX));
     OR(16, R(EAX), R(EDX));
-    LEA(16, EDX, MScaled(EDX, SCALE_8, 0));
+    SHL(16, R(EDX), Imm8(3));
     NOT(16, R(EAX));
     OR(16, R(EAX), R(EDX));
     TEST(16, R(EAX), Imm16(0x20));
diff --git a/Source/Core/Core/DSP/Jit/x64/DSPJitMultiplier.cpp b/Source/Core/Core/DSP/Jit/x64/DSPJitMultiplier.cpp
index 79e6252f12..63acadc559 100644
--- a/Source/Core/Core/DSP/Jit/x64/DSPJitMultiplier.cpp
+++ b/Source/Core/Core/DSP/Jit/x64/DSPJitMultiplier.cpp
@@ -30,7 +30,7 @@ void DSPEmitter::multiply()
   TEST(16, sr_reg, Imm16(SR_MUL_MODIFY));
   FixupBranch noMult2 = J_CC(CC_NZ);
   //		prod <<= 1;
-  LEA(64, RAX, MRegSum(RAX, RAX));
+  ADD(64, R(RAX), R(RAX));
   SetJumpTarget(noMult2);
   m_gpr.PutReg(DSP_REG_SR, false);
   //	return prod;
@@ -130,7 +130,7 @@ void DSPEmitter::multiply_mulx(u8 axh0, u8 axh1)
   TEST(16, sr_reg, Imm16(SR_MUL_MODIFY));
   FixupBranch noMult2 = J_CC(CC_NZ);
   //		prod <<= 1;
-  LEA(64, RAX, MRegSum(RAX, RAX));
+  ADD(64, R(RAX), R(RAX));
   SetJumpTarget(noMult2);
   m_gpr.PutReg(DSP_REG_SR, false);
   //	return prod;