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[InstSimplify] fold insertelement-of-extractelement

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This was partly handled in InstCombine (only the constant
index case), so delete that and zap it more generally in
InstSimplify.

llvm-svn: 361576
This commit is contained in:
Sanjay Patel 2019-05-24 00:13:58 +00:00
parent 4c5bf0241a
commit 80789faf83
3 changed files with 8 additions and 11 deletions
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6
lib/Analysis/InstructionSimplify.cpp
View File

@ -4016,6 +4016,12 @@ Value *llvm::SimplifyInsertElementInst(Value *Vec, Value *Val, Value *Idx,
if (isa<UndefValue>(Val))
return Vec;
// If we are extracting a value from a vector, then inserting it into the same
// place, that's the input vector:
// insertelt Vec, (extractelt Vec, Idx), Idx --> Vec
if (match(Val, m_ExtractElement(m_Specific(Vec), m_Specific(Idx))))
return Vec;
return nullptr;
}

5
lib/Transforms/InstCombine/InstCombineVectorOps.cpp
View File

@ -884,11 +884,6 @@ Instruction *InstCombiner::visitInsertElementInst(InsertElementInst &IE) {
if (match(IdxOp, m_ConstantInt(InsertedIdx)) &&
match(ScalarOp, m_ExtractElement(m_Value(ExtVecOp),
m_ConstantInt(ExtractedIdx)))) {
// If we are extracting a value from a vector, then inserting it right
// back into the same place, just use the input vector.
if (ExtVecOp == VecOp && ExtractedIdx == InsertedIdx)
return replaceInstUsesWith(IE, VecOp);
// TODO: Looking at the user(s) to determine if this insert is a
// fold-to-shuffle opportunity does not match the usual instcombine
// constraints. We should decide if the transform is worthy based only

8
test/Transforms/InstSimplify/insertelement.ll
View File

@ -52,9 +52,7 @@ define <4 x i32> @PR1286(<4 x i32> %A) {
define <8 x i8> @extract_insert_same_vec_and_index(<8 x i8> %in) {
; CHECK-LABEL: @extract_insert_same_vec_and_index(
; CHECK-NEXT: [[VAL:%.*]] = extractelement <8 x i8> [[IN:%.*]], i32 5
; CHECK-NEXT: [[VEC:%.*]] = insertelement <8 x i8> [[IN]], i8 [[VAL]], i32 5
; CHECK-NEXT: ret <8 x i8> [[VEC]]
; CHECK-NEXT: ret <8 x i8> [[IN:%.*]]
;
%val = extractelement <8 x i8> %in, i32 5
%vec = insertelement <8 x i8> %in, i8 %val, i32 5
@ -63,9 +61,7 @@ define <8 x i8> @extract_insert_same_vec_and_index(<8 x i8> %in) {
define <8 x i8> @extract_insert_same_vec_and_index2(<8 x i8> %in, i32 %index) {
; CHECK-LABEL: @extract_insert_same_vec_and_index2(
; CHECK-NEXT: [[VAL:%.*]] = extractelement <8 x i8> [[IN:%.*]], i32 [[INDEX:%.*]]
; CHECK-NEXT: [[VEC:%.*]] = insertelement <8 x i8> [[IN]], i8 [[VAL]], i32 [[INDEX]]
; CHECK-NEXT: ret <8 x i8> [[VEC]]
; CHECK-NEXT: ret <8 x i8> [[IN:%.*]]
;
%val = extractelement <8 x i8> %in, i32 %index
%vec = insertelement <8 x i8> %in, i8 %val, i32 %index