[InstCombine] Cleanup the TFE/LWE check in AMDGPU SimplifyDemanded

Summary:
The fix added in r352904 is not quite correct, or rather misleading:

1. When the texfailctrl (TFC) argument was non-constant, the fix assumed
   non-TFE/LWE, which is incorrect.

2. Regardless, this code path cannot even be hit for correct
   TFE/LWE-enabled calls, because those return a struct. Added
   a test case for those for completeness.

Change-Id: I92d314dbc67a2670f6d7adaab765ef45f56a49cf

Reviewers: hliao, dstuttard, arsenm

Subscribers: kzhuravl, jvesely, wdng, yaxunl, tpr, t-tye, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D57681

llvm-svn: 353097

2 files changed, 14 insertions, 18 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
index a1c666d48f4..35876a63bcc 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ b/llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -800,8 +800,7 @@ private:
 
   Value *simplifyAMDGCNMemoryIntrinsicDemanded(IntrinsicInst *II,
                                                APInt DemandedElts,
-                                               int DmaskIdx = -1,
-                                               int TFCIdx = -1);
+                                               int DmaskIdx = -1);
 
   Value *SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
                                     APInt &UndefElts, unsigned Depth = 0);
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
index e62faab1308..19cdea69230 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -966,25 +966,16 @@ InstCombiner::simplifyShrShlDemandedBits(Instruction *Shr, const APInt &ShrOp1,
 }
 
 /// Implement SimplifyDemandedVectorElts for amdgcn buffer and image intrinsics.
+///
+/// Note: This only supports non-TFE/LWE image intrinsic calls; those have
+///       struct returns.
 Value *InstCombiner::simplifyAMDGCNMemoryIntrinsicDemanded(IntrinsicInst *II,
                                                            APInt DemandedElts,
-                                                           int DMaskIdx,
-                                                           int TFCIdx) {
+                                                           int DMaskIdx) {
   unsigned VWidth = II->getType()->getVectorNumElements();
   if (VWidth == 1)
     return nullptr;
 
-  // Need to change to new instruction format
-  bool TFELWEEnabled = false;
-  if (TFCIdx > 0) {
-    if (ConstantInt *TFC = dyn_cast<ConstantInt>(II->getArgOperand(TFCIdx)))
-      TFELWEEnabled =    TFC->getZExtValue() & 0x1  // TFE
-                      || TFC->getZExtValue() & 0x2; // LWE
-  }
-
-  if (TFELWEEnabled)
-    return nullptr; // TFE not yet supported
-
   ConstantInt *NewDMask = nullptr;
 
   if (DMaskIdx < 0) {
@@ -1648,9 +1639,15 @@ Value *InstCombiner::SimplifyDemandedVectorElts(Value *V, APInt DemandedElts,
     case Intrinsic::amdgcn_struct_buffer_load_format:
       return simplifyAMDGCNMemoryIntrinsicDemanded(II, DemandedElts);
     default: {
-      if (getAMDGPUImageDMaskIntrinsic(II->getIntrinsicID()))
-        return simplifyAMDGCNMemoryIntrinsicDemanded(
-            II, DemandedElts, 0, II->getNumArgOperands() - 2);
+      if (getAMDGPUImageDMaskIntrinsic(II->getIntrinsicID())) {
+        LLVM_DEBUG(
+          Value *TFC = II->getArgOperand(II->getNumOperands() - 2);
+          assert(!isa<ConstantInt>(TFC) ||
+                 dyn_cast<ConstantInt>(TFC)->getZExtValue() == 0);
+        );
+
+        return simplifyAMDGCNMemoryIntrinsicDemanded(II, DemandedElts, 0);
+      }
 
       break;
     }