[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

1 files changed, 1 insertions, 2 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);