[AMDGPU] Fix a weird WWM intrinsic issue.

I found a really strange WWM issue through a very convoluted shader that
essentially boils down to a bug in SIInstrInfo where canReadVGPR did not
correctly identify that WWM is like a copy and can have a VGPR as its
source.

Differential Revision: https://reviews.llvm.org/D56002

llvm-svn: 352500

1 files changed, 17 insertions, 13 deletions

diff --git a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
index 45687d4486e..b857d9df823 100644
--- a/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
+++ b/llvm/lib/Target/AMDGPU/SIInstrInfo.cpp
@@ -3277,18 +3277,6 @@ const TargetRegisterClass *SIInstrInfo::getOpRegClass(const MachineInstr &MI,
   return RI.getRegClass(RCID);
 }
 
-bool SIInstrInfo::canReadVGPR(const MachineInstr &MI, unsigned OpNo) const {
-  switch (MI.getOpcode()) {
-  case AMDGPU::COPY:
-  case AMDGPU::REG_SEQUENCE:
-  case AMDGPU::PHI:
-  case AMDGPU::INSERT_SUBREG:
-    return RI.hasVGPRs(getOpRegClass(MI, 0));
-  default:
-    return RI.hasVGPRs(getOpRegClass(MI, OpNo));
-  }
-}
-
 void SIInstrInfo::legalizeOpWithMove(MachineInstr &MI, unsigned OpIdx) const {
   MachineBasicBlock::iterator I = MI;
   MachineBasicBlock *MBB = MI.getParent();
@@ -4957,7 +4945,23 @@ void SIInstrInfo::addUsersToMoveToVALUWorklist(
   for (MachineRegisterInfo::use_iterator I = MRI.use_begin(DstReg),
          E = MRI.use_end(); I != E;) {
     MachineInstr &UseMI = *I->getParent();
-    if (!canReadVGPR(UseMI, I.getOperandNo())) {
+
+    unsigned OpNo = 0;
+
+    switch (UseMI.getOpcode()) {
+    case AMDGPU::COPY:
+    case AMDGPU::WQM:
+    case AMDGPU::WWM:
+    case AMDGPU::REG_SEQUENCE:
+    case AMDGPU::PHI:
+    case AMDGPU::INSERT_SUBREG:
+      break;
+    default:
+      OpNo = I.getOperandNo();
+      break;
+    }
+
+    if (!RI.hasVGPRs(getOpRegClass(UseMI, OpNo))) {
       Worklist.insert(&UseMI);
 
       do {