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rotaterightrotateright
committedJan 5, 2016
[InstCombine] insert a new shuffle before its uses (PR26015)
Although this solves the test case in PR26015: https://llvm.org/bugs/show_bug.cgi?id=26015 And may solve PR25999: https://llvm.org/bugs/show_bug.cgi?id=25999 ...I suspect this is not the best solution. I think we want to insert the new shuffle just ahead of the earliest ExtractElementInst that we're replacing, but I don't know how that should be implemented. Differential Revision: http://reviews.llvm.org/D15878 llvm-svn: 256857
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‎llvm/lib/Transforms/InstCombine/InstCombineVectorOps.cpp

+21-8
Original file line numberDiff line numberDiff line change
@@ -383,15 +383,28 @@ static void replaceExtractElements(InsertElementInst *InsElt,
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auto *WideVec = new ShuffleVectorInst(ExtVecOp, UndefValue::get(ExtVecType),
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ConstantVector::get(ExtendMask));
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// Replace all extracts from the original narrow vector with extracts from
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// the new wide vector.
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WideVec->insertBefore(ExtElt);
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// Insert the new shuffle after the vector operand of the extract is defined
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// or at the start of the basic block, so any subsequent extracts can use it.
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bool ReplaceAllExtUsers;
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if (auto *ExtVecOpInst = dyn_cast<Instruction>(ExtVecOp)) {
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WideVec->insertAfter(ExtVecOpInst);
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ReplaceAllExtUsers = true;
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} else {
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// TODO: Insert at start of function, so it's always safe to replace all?
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IC.InsertNewInstWith(WideVec, *ExtElt->getParent()->getFirstInsertionPt());
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ReplaceAllExtUsers = false;
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}
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// Replace extracts from the original narrow vector with extracts from the new
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// wide vector.
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for (User *U : ExtVecOp->users()) {
390-
if (ExtractElementInst *OldExt = dyn_cast<ExtractElementInst>(U)) {
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auto *NewExt = ExtractElementInst::Create(WideVec, OldExt->getOperand(1));
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NewExt->insertAfter(WideVec);
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IC.ReplaceInstUsesWith(*OldExt, NewExt);
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}
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ExtractElementInst *OldExt = dyn_cast<ExtractElementInst>(U);
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if (!OldExt ||
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(!ReplaceAllExtUsers && OldExt->getParent() != WideVec->getParent()))
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continue;
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auto *NewExt = ExtractElementInst::Create(WideVec, OldExt->getOperand(1));
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NewExt->insertAfter(WideVec);
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IC.ReplaceInstUsesWith(*OldExt, NewExt);
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}
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}
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‎llvm/test/Transforms/InstCombine/insert-extract-shuffle.ll

+53
Original file line numberDiff line numberDiff line change
@@ -72,3 +72,56 @@ define <8 x float> @widen_extract4(<8 x float> %ins, <2 x float> %ext) {
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ret <8 x float> %i1
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}
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; PR26015: https://llvm.org/bugs/show_bug.cgi?id=26015
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; The widening shuffle must be inserted before any uses.
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define <8 x i16> @pr26015(<4 x i16> %t0) {
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; CHECK-LABEL: @pr26015(
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; CHECK-NEXT: %[[WIDEVEC:.*]] = shufflevector <4 x i16> %t0, <4 x i16> undef, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
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; CHECK-NEXT: %[[EXT:.*]] = extractelement <4 x i16> %t0, i32 2
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; CHECK-NEXT: %t2 = insertelement <8 x i16> <i16 0, i16 0, i16 0, i16 undef, i16 0, i16 0, i16 undef, i16 undef>, i16 %[[EXT]], i32 3
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; CHECK-NEXT: %t3 = insertelement <8 x i16> %t2, i16 0, i32 6
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; CHECK-NEXT: %t5 = shufflevector <8 x i16> %t3, <8 x i16> %[[WIDEVEC]], <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 11>
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; CHECK-NEXT: ret <8 x i16> %t5
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%t1 = extractelement <4 x i16> %t0, i32 2
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%t2 = insertelement <8 x i16> zeroinitializer, i16 %t1, i32 3
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%t3 = insertelement <8 x i16> %t2, i16 0, i32 6
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%t4 = extractelement <4 x i16> %t0, i32 3
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%t5 = insertelement <8 x i16> %t3, i16 %t4, i32 7
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ret <8 x i16> %t5
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}
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; PR25999: https://llvm.org/bugs/show_bug.cgi?id=25999
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; TODO: The widening shuffle could be inserted at the start of the function to allow the first extract to use it.
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define <8 x i16> @pr25999(<4 x i16> %t0, i1 %b) {
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; CHECK-LABEL: @pr25999(
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; CHECK-NEXT: %t1 = extractelement <4 x i16> %t0, i32 2
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; CHECK-NEXT: br i1 %b, label %if, label %end
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; CHECK: if:
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; CHECK-NEXT: %[[WIDEVEC:.*]] = shufflevector <4 x i16> %t0, <4 x i16> undef, <8 x i32> <i32 undef, i32 undef, i32 undef, i32 3, i32 undef, i32 undef, i32 undef, i32 undef>
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; CHECK-NEXT: %t2 = insertelement <8 x i16> <i16 0, i16 0, i16 0, i16 undef, i16 0, i16 0, i16 undef, i16 undef>, i16 %t1, i32 3
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; CHECK-NEXT: %t3 = insertelement <8 x i16> %t2, i16 0, i32 6
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; CHECK-NEXT: %t5 = shufflevector <8 x i16> %t3, <8 x i16> %[[WIDEVEC]], <8 x i32> <i32 0, i32 1, i32 2, i32 3, i32 4, i32 5, i32 6, i32 11>
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; CHECK-NEXT: ret <8 x i16> %t5
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; CHECK: end:
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; CHECK-NEXT: %a1 = add i16 %t1, 4
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; CHECK-NEXT: %t6 = insertelement <8 x i16> <i16 undef, i16 0, i16 0, i16 0, i16 0, i16 0, i16 0, i16 0>, i16 %a1, i32 0
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; CHECK-NEXT: ret <8 x i16> %t6
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%t1 = extractelement <4 x i16> %t0, i32 2
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br i1 %b, label %if, label %end
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if:
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%t2 = insertelement <8 x i16> zeroinitializer, i16 %t1, i32 3
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%t3 = insertelement <8 x i16> %t2, i16 0, i32 6
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%t4 = extractelement <4 x i16> %t0, i32 3
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%t5 = insertelement <8 x i16> %t3, i16 %t4, i32 7
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ret <8 x i16> %t5
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end:
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%a1 = add i16 %t1, 4
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%t6 = insertelement <8 x i16> zeroinitializer, i16 %a1, i32 0
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ret <8 x i16> %t6
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}
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