From 2134991be8300eb454ab2e779973017ef29f6c46 Mon Sep 17 00:00:00 2001
From: JosJuice <josjuice@gmail.com>
Date: Sat, 31 Aug 2024 12:20:40 +0200
Subject: [PATCH] Jit: Move multiplication by 0 optimization to
 ConstantPropagation

---
 .../Core/Core/PowerPC/Jit64/Jit_Integer.cpp   |  7 ----
 .../PowerPC/JitArm64/JitArm64_Integer.cpp     |  9 +----
 .../PowerPC/JitCommon/ConstantPropagation.cpp | 39 ++++++++++++++++++-
 .../PowerPC/JitCommon/ConstantPropagation.h   |  2 +
 4 files changed, 40 insertions(+), 17 deletions(-)

diff --git a/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp b/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp
index af6723c8214..cdca3274af0 100644
--- a/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp
+++ b/Source/Core/Core/PowerPC/Jit64/Jit_Integer.cpp
@@ -1201,13 +1201,6 @@ void Jit64::MultiplyImmediate(u32 imm, int a, int d, bool overflow)
   RCX64Reg Rd = gpr.Bind(d, RCMode::Write);
   RegCache::Realize(Ra, Rd);
 
-  // simplest cases first
-  if (imm == 0)
-  {
-    XOR(32, Rd, Rd);
-    return;
-  }
-
   if (imm == (u32)-1)
   {
     if (d != a)
diff --git a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
index ebd3dd273aa..1a4027059cd 100644
--- a/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
+++ b/Source/Core/Core/PowerPC/JitArm64/JitArm64_Integer.cpp
@@ -885,14 +885,7 @@ void JitArm64::addic(UGeckoInstruction inst)
 
 bool JitArm64::MultiplyImmediate(u32 imm, int a, int d, bool rc)
 {
-  if (imm == 0)
-  {
-    // Multiplication by zero (0).
-    gpr.SetImmediate(d, 0);
-    if (rc)
-      ComputeRC0(gpr.GetImm(d));
-  }
-  else if (imm == 1)
+  if (imm == 1)
   {
     // Multiplication by one (1).
     if (d != a)
diff --git a/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.cpp b/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.cpp
index 78facf40bd2..980347062b4 100644
--- a/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.cpp
+++ b/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.cpp
@@ -64,6 +64,9 @@ ConstantPropagationResult ConstantPropagation::EvaluateInstruction(UGeckoInstruc
 
 ConstantPropagationResult ConstantPropagation::EvaluateMulImm(UGeckoInstruction inst) const
 {
+  if (inst.SIMM_16 == 0)
+    return ConstantPropagationResult(inst.RD, 0);
+
   if (!HasGPR(inst.RA))
     return {};
 
@@ -202,8 +205,17 @@ ConstantPropagationResult ConstantPropagation::EvaluateTable31S(UGeckoInstructio
 ConstantPropagationResult ConstantPropagation::EvaluateTable31AB(UGeckoInstruction inst,
                                                                  u64 flags) const
 {
-  if (!HasGPR(inst.RA, inst.RB))
-    return {};
+  const bool has_a = HasGPR(inst.RA);
+  const bool has_b = HasGPR(inst.RB);
+  if (!has_a || !has_b)
+  {
+    if (has_a)
+      return EvaluateTable31ABOneRegisterKnown(inst, flags, GetGPR(inst.RA));
+    else if (has_b)
+      return EvaluateTable31ABOneRegisterKnown(inst, flags, GetGPR(inst.RB));
+    else
+      return {};
+  }
 
   u64 d;
   s64 d_overflow;
@@ -241,6 +253,29 @@ ConstantPropagationResult ConstantPropagation::EvaluateTable31AB(UGeckoInstructi
   return result;
 }
 
+ConstantPropagationResult
+ConstantPropagation::EvaluateTable31ABOneRegisterKnown(UGeckoInstruction inst, u64 flags,
+                                                       u32 value) const
+{
+  switch (inst.SUBOP10)
+  {
+  case 11:   // mulhwux
+  case 75:   // mulhwx
+  case 235:  // mullwx
+  case 747:  // mullwox
+    if (value == 0)
+    {
+      ConstantPropagationResult result(inst.RD, 0, inst.Rc);
+      if (flags & FL_SET_OE)
+        result.overflow = false;
+      return result;
+    }
+    break;
+  }
+
+  return {};
+}
+
 ConstantPropagationResult ConstantPropagation::EvaluateTable31SB(UGeckoInstruction inst) const
 {
   const bool has_s = HasGPR(inst.RS);
diff --git a/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.h b/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.h
index 9b8070caf1b..4ff7823aa44 100644
--- a/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.h
+++ b/Source/Core/Core/PowerPC/JitCommon/ConstantPropagation.h
@@ -87,6 +87,8 @@ private:
   ConstantPropagationResult EvaluateTable31Negx(UGeckoInstruction inst, u64 flags) const;
   ConstantPropagationResult EvaluateTable31S(UGeckoInstruction inst) const;
   ConstantPropagationResult EvaluateTable31AB(UGeckoInstruction inst, u64 flags) const;
+  ConstantPropagationResult EvaluateTable31ABOneRegisterKnown(UGeckoInstruction inst, u64 flags,
+                                                              u32 value) const;
   ConstantPropagationResult EvaluateTable31SB(UGeckoInstruction inst) const;
   ConstantPropagationResult EvaluateTable31SBOneRegisterKnown(UGeckoInstruction inst, u32 value,
                                                               bool known_reg_is_b) const;