[llvm] r255126 - Revert "[InstCombine] fold bitcasts around an extractelement"

Mehdi Amini via llvm-commits llvm-commits at lists.llvm.org
Wed Dec 9 08:31:40 PST 2015


Author: mehdi_amini
Date: Wed Dec  9 10:31:39 2015
New Revision: 255126

URL: http://llvm.org/viewvc/llvm-project?rev=255126&view=rev
Log:
Revert "[InstCombine] fold bitcasts around an extractelement"

This reverts commit r255124.

Broke http://lab.llvm.org:8011/builders/llvm-clang-lld-x86_64-scei-ps4-ubuntu-fast/builds/4193/steps/test/logs/stdio

From: Mehdi Amini <mehdi.amini at apple.com>

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
    llvm/trunk/test/Transforms/InstCombine/bitcast.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=255126&r1=255125&r2=255126&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Wed Dec  9 10:31:39 2015
@@ -1715,40 +1715,6 @@ static Value *optimizeIntegerToVectorIns
   return Result;
 }
 
-/// Given a bitcasted vector fed into an extract element instruction and then
-/// bitcasted again, eliminate at least one bitcast by changing the vector type
-/// of the extractelement instruction.
-/// Example:
-///   bitcast (extractelement (bitcast <2 x float> %X to <2 x i32>), 1) to float
-///    --->
-///   extractelement <2 x float> %X, i32 1
-static Instruction *foldBitCastExtElt(BitCastInst &BitCast, InstCombiner &IC,
-                                      const DataLayout &DL) {
-  // TODO: Create and use a pattern matcher for ExtractElementInst.
-  auto *ExtElt = dyn_cast<ExtractElementInst>(BitCast.getOperand(0));
-  if (!ExtElt || !ExtElt->hasOneUse())
-    return nullptr;
-
-  Value *InnerBitCast = nullptr;
-  if (!match(ExtElt->getOperand(0), m_BitCast(m_Value(InnerBitCast))))
-    return nullptr;
-
-  VectorType *VecType = cast<VectorType>(InnerBitCast->getType());
-  Type *DestType = BitCast.getType();
-
-  // If the element type of the vector doesn't match the result type,
-  // bitcast it to a vector type that we can extract from.
-  if (VecType->getElementType() != DestType) {
-    unsigned VecWidth = VecType->getPrimitiveSizeInBits();
-    unsigned DestWidth = DestType->getPrimitiveSizeInBits();
-    unsigned NumElts = VecWidth / DestWidth;
-    VecType = VectorType::get(DestType, NumElts);
-    InnerBitCast = IC.Builder->CreateBitCast(InnerBitCast, VecType, "bc");
-  }
-
-  return ExtractElementInst::Create(InnerBitCast, ExtElt->getOperand(1));
-}
-
 static Instruction *foldVecTruncToExtElt(Value *VecInput, Type *DestTy,
                                          unsigned ShiftAmt, InstCombiner &IC,
                                          const DataLayout &DL) {
@@ -1920,9 +1886,6 @@ Instruction *InstCombiner::visitBitCast(
     }
   }
 
-  if (Instruction *I = foldBitCastExtElt(CI, *this, DL))
-    return I;
-
   if (SrcTy->isPointerTy())
     return commonPointerCastTransforms(CI);
   return commonCastTransforms(CI);

Modified: llvm/trunk/test/Transforms/InstCombine/bitcast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/bitcast.ll?rev=255126&r1=255125&r2=255126&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/bitcast.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/bitcast.ll Wed Dec  9 10:31:39 2015
@@ -64,7 +64,7 @@ define float @test3(<2 x float> %A, <2 x
 ; CHECK-NEXT:  ret float %add
 }
 
-; Both bitcasts are unnecessary; change the extractelement.
+; TODO: Both bitcasts are unnecessary; change the extractelement.
 
 define float @bitcast_extelt1(<2 x float> %A) {
   %bc1 = bitcast <2 x float> %A to <2 x i32>
@@ -73,11 +73,13 @@ define float @bitcast_extelt1(<2 x float
   ret float %bc2
 
 ; CHECK-LABEL: @bitcast_extelt1(
-; CHECK-NEXT:  %bc2 = extractelement <2 x float> %A, i32 0
+; CHECK-NEXT:  %bc1 = bitcast <2 x float> %A to <2 x i32>
+; CHECK-NEXT:  %ext = extractelement <2 x i32> %bc1, i32 0
+; CHECK-NEXT:  %bc2 = bitcast i32 %ext to float
 ; CHECK-NEXT:  ret float %bc2
 }
 
-; Second bitcast can be folded into the first.
+; TODO: Second bitcast can be folded into the first.
 
 define i64 @bitcast_extelt2(<4 x float> %A) {
   %bc1 = bitcast <4 x float> %A to <2 x double>
@@ -86,8 +88,9 @@ define i64 @bitcast_extelt2(<4 x float>
   ret i64 %bc2
 
 ; CHECK-LABEL: @bitcast_extelt2(
-; CHECK-NEXT:  %bc = bitcast <4 x float> %A to <2 x i64>
-; CHECK-NEXT:  %bc2 = extractelement <2 x i64> %bc, i32 1
+; CHECK-NEXT:  %bc1 = bitcast <4 x float> %A to <2 x double>
+; CHECK-NEXT:  %ext = extractelement <2 x double> %bc1, i32 1
+; CHECK-NEXT:  %bc2 = bitcast double %ext to i64
 ; CHECK-NEXT:  ret i64 %bc2
 }
 




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