Rebase and address reviewer comments

Author: dc03-work

llvm/include/llvm/CodeGen/GlobalISel/GenericMachineInstrs.h

@@ -36,9 +36,8 @@ class GenericMachineInstr : public MachineInstr {
   }
 
   bool hasPoisonGeneratingFlags() const {
-    return getFlag(NoUWrap) || getFlag(NoSWrap) || getFlag(IsExact) ||
-           getFlag(Disjoint) || getFlag(NonNeg) || getFlag(FmNoNans) ||
-           getFlag(FmNoInfs);
+    return getFlags() & (NoUWrap | NoSWrap | IsExact | Disjoint | NonNeg |
+                         FmNoNans | FmNoInfs);
   }
 
   void dropPoisonGeneratingFlags() {

llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp

@@ -229,18 +229,16 @@ bool CombinerHelper::matchFreezeOfSingleMaybePoisonOperand(
   Register DstOp = MI.getOperand(0).getReg();
   Register OrigOp = MI.getOperand(1).getReg();
 
-  if (OrigOp.isPhysical() || !MRI.hasOneNonDBGUse(OrigOp))
+  if (!MRI.hasOneNonDBGUse(OrigOp))
     return false;
 
   MachineInstr *OrigDef = MRI.getUniqueVRegDef(OrigOp);
-  // Avoid trying to fold G_PHI, G_UNMERGE_VALUES, G_FREEZE (the latter is
-  // handled by idempotent_prop).
-  if (!OrigDef || OrigDef->isPHI() || isa<GUnmerge>(OrigDef) ||
-      isa<GFreeze>(OrigDef))
+  // Avoid trying to fold G_PHI and G_UNMERGE_VALUES.
+  if (OrigDef->isPHI() || isa<GUnmerge>(OrigDef))
     return false;
 
   if (canCreateUndefOrPoison(OrigOp, MRI,
-                             /*ConsiderFlagsAndMetadata*/ false))
+                             /*ConsiderFlagsAndMetadata=*/false))
     return false;
 
   std::optional<MachineOperand> MaybePoisonOperand;
@@ -254,9 +252,11 @@ bool CombinerHelper::matchFreezeOfSingleMaybePoisonOperand(
 
     if (!MaybePoisonOperand)
       MaybePoisonOperand = Operand;
-    // We have more than one maybe-poison operand. Moving the freeze is unsafe.
-    else
+    else {
+      // We have more than one maybe-poison operand. Moving the freeze is
+      // unsafe.
       return false;
+    }
   }
 
   cast<GenericMachineInstr>(OrigDef)->dropPoisonGeneratingFlags();
@@ -271,11 +271,11 @@ bool CombinerHelper::matchFreezeOfSingleMaybePoisonOperand(
   LLT MaybePoisonOperandRegTy = MRI.getType(MaybePoisonOperandReg);
 
   MatchInfo = [=](MachineIRBuilder &B) mutable {
-    auto Reg = MRI.createGenericVirtualRegister(MaybePoisonOperandRegTy);
     B.setInsertPt(*OrigDef->getParent(), OrigDef->getIterator());
-    B.buildFreeze(Reg, MaybePoisonOperandReg);
+    auto Freeze = B.buildFreeze(MaybePoisonOperandRegTy, MaybePoisonOperandReg);
     replaceRegOpWith(
-        MRI, *OrigDef->findRegisterUseOperand(MaybePoisonOperandReg, TRI), Reg);
+        MRI, *OrigDef->findRegisterUseOperand(MaybePoisonOperandReg, TRI),
+        Freeze.getReg(0));
     replaceRegWith(MRI, DstOp, OrigOp);
   };
   return true;

llvm/lib/CodeGen/GlobalISel/Utils.cpp

@@ -1737,18 +1737,16 @@ static bool canCreateUndefOrPoison(Register Reg, const MachineRegisterInfo &MRI,
     if (ConsiderFlagsAndMetadata && includesPoison(Kind) &&
         GMI->hasPoisonGeneratingFlags())
       return true;
-  }
-  // Conservatively return true.
-  else
+  } else {
+    // Conservatively return true.
     return true;
+  }
 
   switch (RegDef->getOpcode()) {
   case TargetOpcode::G_FREEZE:
     return false;
   default:
-    if (isa<GCastOp>(RegDef) || isa<GBinOp>(RegDef))
-      return false;
-    return true;
+    return !isa<GCastOp>(RegDef) && !isa<GBinOp>(RegDef);
   }
 }