[AMDGPU] Remove GCNRewritePartialRegUsesImpl::getOperandRegClass

[jayfoad]

No description provided.

[llvmbot]

@llvm/pr-subscribers-backend-amdgpu

Author: Jay Foad (jayfoad)

Changes

---

Full diff: https://github.com/llvm/llvm-project/pull/135153.diff

1 Files Affected:

• (modified) llvm/lib/Target/AMDGPU/GCNRewritePartialRegUses.cpp (-18)

diff --git a/llvm/lib/Target/AMDGPU/GCNRewritePartialRegUses.cpp b/llvm/lib/Target/AMDGPU/GCNRewritePartialRegUses.cpp
index c58d1b00a1002..4988eaa1a947d 100644
--- a/llvm/lib/Target/AMDGPU/GCNRewritePartialRegUses.cpp
+++ b/llvm/lib/Target/AMDGPU/GCNRewritePartialRegUses.cpp
@@ -105,9 +105,6 @@ class GCNRewritePartialRegUsesImpl {
 
   /// Helper methods.
 
-  /// Return reg class expected by a MO's parent instruction for a given MO.
-  const TargetRegisterClass *getOperandRegClass(MachineOperand &MO) const;
-
   /// Find right-shifted by RShift amount version of the SubReg if it exists,
   /// return 0 otherwise.
   unsigned shiftSubReg(unsigned SubReg, unsigned RShift) const;
@@ -404,13 +401,6 @@ void GCNRewritePartialRegUsesImpl::updateLiveIntervals(
   LIS->removeInterval(OldReg);
 }
 
-const TargetRegisterClass *
-GCNRewritePartialRegUsesImpl::getOperandRegClass(MachineOperand &MO) const {
-  MachineInstr *MI = MO.getParent();
-  return TII->getRegClass(TII->get(MI->getOpcode()), MI->getOperandNo(&MO), TRI,
-                          *MI->getParent()->getParent());
-}
-
 bool GCNRewritePartialRegUsesImpl::rewriteReg(Register Reg) const {
   auto Range = MRI->reg_nodbg_operands(Reg);
   if (Range.empty() || any_of(Range, [](MachineOperand &MO) {
@@ -436,14 +426,6 @@ bool GCNRewritePartialRegUsesImpl::rewriteReg(Register Reg) const {
     if (Inserted)
       SubRegRC = TRI->getSubRegisterClass(RC, SubReg);
 
-    if (SubRegRC) {
-      if (const TargetRegisterClass *OpDescRC = getOperandRegClass(MO)) {
-        LLVM_DEBUG(dbgs() << TRI->getRegClassName(SubRegRC) << " & "
-                          << TRI->getRegClassName(OpDescRC) << " = ");
-        SubRegRC = TRI->getCommonSubClass(SubRegRC, OpDescRC);
-      }
-    }
-
     if (!SubRegRC) {
       LLVM_DEBUG(dbgs() << "couldn't find target regclass\n");
       return false;

[jayfoad]

I can't find any test case where this is needed. If getSubRegisterClass returns an exact match (i.e. not a superclass of what you ask for) then I guess it doesn't need to be constrained any more than the original RC was.

[jayfoad]

I suspect this can be an assert now.

[vpykhtin]

Thanks Jay, this reminds me that I have a cleanup patch for this pass that removes some leftover hacks existed before #67245. I don't mind submitting this but I would like to take a look into my patch and remember what I did.

More details available here #69957

[jayfoad]

Superseded by #135199.