[llvm] r256857 - [InstCombine] insert a new shuffle before its uses (PR26015)
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Tue Jan 5 11:09:47 PST 2016
Author: spatel
Date: Tue Jan 5 13:09:47 2016
New Revision: 256857
URL: http://llvm.org/viewvc/llvm-project?rev=256857&view=rev
Log:
[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
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp?rev=256857&r1=256856&r2=256857&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineVectorOps.cpp Tue Jan 5 13:09:47 2016
@@ -383,15 +383,28 @@ static void replaceExtractElements(Inser
auto *WideVec = new ShuffleVectorInst(ExtVecOp, UndefValue::get(ExtVecType),
ConstantVector::get(ExtendMask));
- // Replace all extracts from the original narrow vector with extracts from
- // the new wide vector.
- WideVec->insertBefore(ExtElt);
+ // Insert the new shuffle after the vector operand of the extract is defined
+ // or at the start of the basic block, so any subsequent extracts can use it.
+ bool ReplaceAllExtUsers;
+ if (auto *ExtVecOpInst = dyn_cast<Instruction>(ExtVecOp)) {
+ WideVec->insertAfter(ExtVecOpInst);
+ ReplaceAllExtUsers = true;
+ } else {
+ // TODO: Insert at start of function, so it's always safe to replace all?
+ IC.InsertNewInstWith(WideVec, *ExtElt->getParent()->getFirstInsertionPt());
+ ReplaceAllExtUsers = false;
+ }
+
+ // Replace extracts from the original narrow vector with extracts from the new
+ // wide vector.
for (User *U : ExtVecOp->users()) {
- if (ExtractElementInst *OldExt = dyn_cast<ExtractElementInst>(U)) {
- auto *NewExt = ExtractElementInst::Create(WideVec, OldExt->getOperand(1));
- NewExt->insertAfter(WideVec);
- IC.ReplaceInstUsesWith(*OldExt, NewExt);
- }
+ ExtractElementInst *OldExt = dyn_cast<ExtractElementInst>(U);
+ if (!OldExt ||
+ (!ReplaceAllExtUsers && OldExt->getParent() != WideVec->getParent()))
+ continue;
+ auto *NewExt = ExtractElementInst::Create(WideVec, OldExt->getOperand(1));
+ NewExt->insertAfter(WideVec);
+ IC.ReplaceInstUsesWith(*OldExt, NewExt);
}
}
Modified: llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll?rev=256857&r1=256856&r2=256857&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/insert-extract-shuffle.ll Tue Jan 5 13:09:47 2016
@@ -72,3 +72,56 @@ define <8 x float> @widen_extract4(<8 x
ret <8 x float> %i1
}
+; PR26015: https://llvm.org/bugs/show_bug.cgi?id=26015
+; The widening shuffle must be inserted before any uses.
+
+define <8 x i16> @pr26015(<4 x i16> %t0) {
+; CHECK-LABEL: @pr26015(
+; 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>
+; CHECK-NEXT: %[[EXT:.*]] = extractelement <4 x i16> %t0, i32 2
+; 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
+; CHECK-NEXT: %t3 = insertelement <8 x i16> %t2, i16 0, i32 6
+; 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>
+; CHECK-NEXT: ret <8 x i16> %t5
+ %t1 = extractelement <4 x i16> %t0, i32 2
+ %t2 = insertelement <8 x i16> zeroinitializer, i16 %t1, i32 3
+ %t3 = insertelement <8 x i16> %t2, i16 0, i32 6
+ %t4 = extractelement <4 x i16> %t0, i32 3
+ %t5 = insertelement <8 x i16> %t3, i16 %t4, i32 7
+ ret <8 x i16> %t5
+}
+
+; PR25999: https://llvm.org/bugs/show_bug.cgi?id=25999
+; TODO: The widening shuffle could be inserted at the start of the function to allow the first extract to use it.
+
+define <8 x i16> @pr25999(<4 x i16> %t0, i1 %b) {
+; CHECK-LABEL: @pr25999(
+; CHECK-NEXT: %t1 = extractelement <4 x i16> %t0, i32 2
+; CHECK-NEXT: br i1 %b, label %if, label %end
+; CHECK: if:
+; 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>
+; 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
+; CHECK-NEXT: %t3 = insertelement <8 x i16> %t2, i16 0, i32 6
+; 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>
+; CHECK-NEXT: ret <8 x i16> %t5
+; CHECK: end:
+; CHECK-NEXT: %a1 = add i16 %t1, 4
+; 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
+; CHECK-NEXT: ret <8 x i16> %t6
+
+ %t1 = extractelement <4 x i16> %t0, i32 2
+ br i1 %b, label %if, label %end
+
+if:
+ %t2 = insertelement <8 x i16> zeroinitializer, i16 %t1, i32 3
+ %t3 = insertelement <8 x i16> %t2, i16 0, i32 6
+ %t4 = extractelement <4 x i16> %t0, i32 3
+ %t5 = insertelement <8 x i16> %t3, i16 %t4, i32 7
+ ret <8 x i16> %t5
+
+end:
+ %a1 = add i16 %t1, 4
+ %t6 = insertelement <8 x i16> zeroinitializer, i16 %a1, i32 0
+ ret <8 x i16> %t6
+}
+
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