[llvm] [X86] X86FixupInstTuning - add dbg message for each instruction replacement (PR #144083)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon created https://github.com/llvm/llvm-project/pull/144083

Help debug the changes the pass makes

>From 6257b08f7025701a159f094627057b28b2bd9e6e Mon Sep 17 00:00:00 2001
From: Simon Pilgrim <llvm-dev at redking.me.uk>
Date: Fri, 13 Jun 2025 15:19:30 +0100
Subject: [PATCH] [X86] X86FixupInstTuning - add dbg message for each
 instruction replacement

Help debug the changes the pass makes
---
 llvm/lib/Target/X86/X86FixupInstTuning.cpp | 57 +++++++++++++++-------
 1 file changed, 40 insertions(+), 17 deletions(-)

diff --git a/llvm/lib/Target/X86/X86FixupInstTuning.cpp b/llvm/lib/Target/X86/X86FixupInstTuning.cpp
index 8c1ff523c975a..89093b2e1a3f5 100644
--- a/llvm/lib/Target/X86/X86FixupInstTuning.cpp
+++ b/llvm/lib/Target/X86/X86FixupInstTuning.cpp
@@ -132,11 +132,15 @@ bool X86FixupInstTuningPass::processInstruction(
   auto ProcessVPERMILPDri = [&](unsigned NewOpc) -> bool {
     if (!NewOpcPreferable(NewOpc))
       return false;
-    unsigned MaskImm = MI.getOperand(NumOperands - 1).getImm();
-    MI.removeOperand(NumOperands - 1);
-    MI.addOperand(MI.getOperand(NumOperands - 2));
-    MI.setDesc(TII->get(NewOpc));
-    MI.addOperand(MachineOperand::CreateImm(MaskImm));
+    LLVM_DEBUG(dbgs() << "Replacing: " << MI);
+    {
+      unsigned MaskImm = MI.getOperand(NumOperands - 1).getImm();
+      MI.removeOperand(NumOperands - 1);
+      MI.addOperand(MI.getOperand(NumOperands - 2));
+      MI.setDesc(TII->get(NewOpc));
+      MI.addOperand(MachineOperand::CreateImm(MaskImm));
+    }
+    LLVM_DEBUG(dbgs() << "     With: " << MI);
     return true;
   };
 
@@ -147,11 +151,15 @@ bool X86FixupInstTuningPass::processInstruction(
   auto ProcessVPERMILPSri = [&](unsigned NewOpc) -> bool {
     if (!NewOpcPreferable(NewOpc))
       return false;
-    unsigned MaskImm = MI.getOperand(NumOperands - 1).getImm();
-    MI.removeOperand(NumOperands - 1);
-    MI.addOperand(MI.getOperand(NumOperands - 2));
-    MI.setDesc(TII->get(NewOpc));
-    MI.addOperand(MachineOperand::CreateImm(MaskImm));
+    LLVM_DEBUG(dbgs() << "Replacing: " << MI);
+    {
+      unsigned MaskImm = MI.getOperand(NumOperands - 1).getImm();
+      MI.removeOperand(NumOperands - 1);
+      MI.addOperand(MI.getOperand(NumOperands - 2));
+      MI.setDesc(TII->get(NewOpc));
+      MI.addOperand(MachineOperand::CreateImm(MaskImm));
+    }
+    LLVM_DEBUG(dbgs() << "     With: " << MI);
     return true;
   };
 
@@ -164,7 +172,11 @@ bool X86FixupInstTuningPass::processInstruction(
     if (!ST->hasNoDomainDelayShuffle() ||
         !NewOpcPreferable(NewOpc, /*ReplaceInTie*/ false))
       return false;
-    MI.setDesc(TII->get(NewOpc));
+    LLVM_DEBUG(dbgs() << "Replacing: " << MI);
+    {
+      MI.setDesc(TII->get(NewOpc));
+    }
+    LLVM_DEBUG(dbgs() << "     With: " << MI);
     return true;
   };
 
@@ -185,9 +197,12 @@ bool X86FixupInstTuningPass::processInstruction(
   auto ProcessUNPCK = [&](unsigned NewOpc, unsigned MaskImm) -> bool {
     if (!NewOpcPreferable(NewOpc, /*ReplaceInTie*/ false))
       return false;
-
-    MI.setDesc(TII->get(NewOpc));
-    MI.addOperand(MachineOperand::CreateImm(MaskImm));
+    LLVM_DEBUG(dbgs() << "Replacing: " << MI);
+    {
+      MI.setDesc(TII->get(NewOpc));
+      MI.addOperand(MachineOperand::CreateImm(MaskImm));
+    }
+    LLVM_DEBUG(dbgs() << "     With: " << MI);
     return true;
   };
 
@@ -198,7 +213,11 @@ bool X86FixupInstTuningPass::processInstruction(
     if (!ST->hasNoDomainDelayShuffle() ||
         !NewOpcPreferable(NewOpc, /*ReplaceInTie*/ false))
       return false;
-    MI.setDesc(TII->get(NewOpc));
+    LLVM_DEBUG(dbgs() << "Replacing: " << MI);
+    {
+      MI.setDesc(TII->get(NewOpc));
+    }
+    LLVM_DEBUG(dbgs() << "     With: " << MI);
     return true;
   };
 
@@ -229,8 +248,12 @@ bool X86FixupInstTuningPass::processInstruction(
       return false;
     if (!OptSize && !NewOpcPreferable(MovOpc))
       return false;
-    MI.setDesc(TII->get(MovOpc));
-    MI.removeOperand(NumOperands - 1);
+    LLVM_DEBUG(dbgs() << "Replacing: " << MI);
+    {
+      MI.setDesc(TII->get(MovOpc));
+      MI.removeOperand(NumOperands - 1);
+    }
+    LLVM_DEBUG(dbgs() << "     With: " << MI);
     return true;
   };