[AMDGPU] SIFoldOperands: try harder to fold cndmask instructions

Look through copies to find more cases where the two values being
selected are identical. The motivation for this is just to be able to
remove the weird special case where tryFoldCndMask was called from
foldInstOperand, part way through folding a move-immediate into its
users, without regressing any lit tests.

diff --git a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
index d279365..6de34dc 100644 (file)
--- a/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
+++ b/llvm/lib/Target/AMDGPU/SIFoldOperands.cpp
@@ -1155,8 +1155,12 @@ bool SIFoldOperands::tryFoldCndMask(MachineInstr &MI) const {
 
   MachineOperand *Src0 = TII->getNamedOperand(MI, AMDGPU::OpName::src0);
   MachineOperand *Src1 = TII->getNamedOperand(MI, AMDGPU::OpName::src1);
-  if (!Src1->isIdenticalTo(*Src0))
-    return false;
+  if (!Src1->isIdenticalTo(*Src0)) {
+    auto *Src0Imm = getImmOrMaterializedImm(*MRI, *Src0);
+    auto *Src1Imm = getImmOrMaterializedImm(*MRI, *Src1);
+    if (!Src1Imm->isIdenticalTo(*Src0Imm))
+      return false;
+  }
 
   int Src1ModIdx =
       AMDGPU::getNamedOperandIdx(Opc, AMDGPU::OpName::src1_modifiers);
@@ -1276,11 +1280,8 @@ void SIFoldOperands::foldInstOperand(MachineInstr &MI,
   for (MachineInstr *Copy : CopiesToReplace)
     Copy->addImplicitDefUseOperands(*MF);
 
-  SmallPtrSet<MachineInstr *, 16> Folded;
   for (FoldCandidate &Fold : FoldList) {
     assert(!Fold.isReg() || Fold.OpToFold);
-    if (Folded.count(Fold.UseMI))
-      continue;
     if (Fold.isReg() && Fold.OpToFold->getReg().isVirtual()) {
       Register Reg = Fold.OpToFold->getReg();
       MachineInstr *DefMI = Fold.OpToFold->getParent();
@@ -1300,8 +1301,6 @@ void SIFoldOperands::foldInstOperand(MachineInstr &MI,
       LLVM_DEBUG(dbgs() << "Folded source from " << MI << " into OpNo "
                         << static_cast<int>(Fold.UseOpNo) << " of "
                         << *Fold.UseMI);
-      if (tryFoldCndMask(*Fold.UseMI))
-        Folded.insert(Fold.UseMI);
     } else if (Fold.isCommuted()) {
       // Restoring instruction's original operand order if fold has failed.
       TII->commuteInstruction(*Fold.UseMI, false);

diff --git a/llvm/test/CodeGen/AMDGPU/fold-cndmask-wave32.mir b/llvm/test/CodeGen/AMDGPU/fold-cndmask-wave32.mir
index a921ce3..c22e025 100644 (file)
--- a/llvm/test/CodeGen/AMDGPU/fold-cndmask-wave32.mir
+++ b/llvm/test/CodeGen/AMDGPU/fold-cndmask-wave32.mir
@@ -11,7 +11,7 @@ body:             |
     ; CHECK: [[DEF:%[0-9]+]]:sreg_32_xm0_xexec = IMPLICIT_DEF
     ; CHECK: [[S_MOV_B32_:%[0-9]+]]:sreg_32 = S_MOV_B32 0
     ; CHECK: [[V_MOV_B32_e32_:%[0-9]+]]:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
-    ; CHECK: [[COPY:%[0-9]+]]:vgpr_32 = COPY [[S_MOV_B32_]]
+    ; CHECK: [[V_MOV_B32_e32_1:%[0-9]+]]:vgpr_32 = V_MOV_B32_e32 0, implicit $exec
     %0:sreg_32_xm0_xexec = IMPLICIT_DEF
     %1:sreg_32 = S_MOV_B32 0
     %2:vgpr_32 = COPY %1:sreg_32