[PATCH] D74139: AMDGPU: Remove dead paths for requiresUniformRegister

[Matt Arsenault via Phabricator via llvm-commits]

arsenm created this revision.
arsenm added reviewers: alex-t, nhaehnle, sameerds, rampitec, kerbowa.
Herald added subscribers: hiraditya, t-tye, tpr, dstuttard, yaxunl, wdng, jvesely, kzhuravl.
Herald added a project: LLVM.

The extracts from control flow intrinsics are already properly
handled. The inline asm case isn't dead, but has also never really
 worked correctly so leave it as-is for now.


https://reviews.llvm.org/D74139

Files:
  llvm/lib/Target/AMDGPU/SIISelLowering.cpp


Index: llvm/lib/Target/AMDGPU/SIISelLowering.cpp
===================================================================
--- llvm/lib/Target/AMDGPU/SIISelLowering.cpp
+++ llvm/lib/Target/AMDGPU/SIISelLowering.cpp
@@ -10868,6 +10868,10 @@
   return RC;
 }
 
+// FIXME: This is a workaround for DivergenceAnalysis not understanding always
+// uniform values (as produced by the mask results of control flow intrinsics)
+// used outside of divergent blocks. The phi users need to also be treated as
+// always uniform.
 static bool hasCFUser(const Value *V, SmallPtrSet<const Value *, 16> &Visited) {
   if (!isa<Instruction>(V))
     return false;
@@ -10910,32 +10914,13 @@
 
 bool SITargetLowering::requiresUniformRegister(MachineFunction &MF,
                                                const Value *V) const {
-  if (const IntrinsicInst *Intrinsic = dyn_cast<IntrinsicInst>(V)) {
-    switch (Intrinsic->getIntrinsicID()) {
-    default:
-      return false;
-    case Intrinsic::amdgcn_if_break:
-      return true;
-    }
-  }
-  if (const ExtractValueInst *ExtValue = dyn_cast<ExtractValueInst>(V)) {
-    if (const IntrinsicInst *Intrinsic =
-            dyn_cast<IntrinsicInst>(ExtValue->getOperand(0))) {
-      switch (Intrinsic->getIntrinsicID()) {
-      default:
-        return false;
-      case Intrinsic::amdgcn_if:
-      case Intrinsic::amdgcn_else: {
-        ArrayRef<unsigned> Indices = ExtValue->getIndices();
-        if (Indices.size() == 1 && Indices[0] == 1) {
-          return true;
-        }
-      }
-      }
-    }
-  }
   if (const CallInst *CI = dyn_cast<CallInst>(V)) {
     if (isa<InlineAsm>(CI->getCalledValue())) {
+      // FIXME: This cannot give a correct answer. This should only trigger in
+      // the case where inline asm returns mixed SGPR and VGPR results, used
+      // outside the defining block. We don't have a specific result to
+      // consider, so this assumes if any value is SGPR, the overall register
+      // also needs to be SGPR.
       const SIRegisterInfo *SIRI = Subtarget->getRegisterInfo();
       ImmutableCallSite CS(CI);
       TargetLowering::AsmOperandInfoVector TargetConstraints = ParseConstraints(


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