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[DSE] Handle memmove with equal non-const sizes
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Follow up for fhahn's D98284. Also fixes a case from PR47644.

Reviewed By: fhahn

Differential Revision: https://reviews.llvm.org/D98346
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@davidbolvansky
davidbolvansky committed Mar 10, 2021
1 parent 077dc5c commit c68b560
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Showing 2 changed files with 158 additions and 16 deletions.
24 changes: 8 additions & 16 deletions llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -373,22 +373,14 @@ isOverwrite(const Instruction *LaterI, const Instruction *EarlierI,
if (!Later.Size.isPrecise() || !Earlier.Size.isPrecise()) {
// In case no constant size is known, try to an IR values for the number
// of bytes written and check if they match.
auto GetSizeFromInstr = [](const Instruction *I) -> Value * {
if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
default:
return nullptr;
case Intrinsic::memcpy:
case Intrinsic::memset:
return II->getArgOperand(2);
}
}
return nullptr;
};
Value *LaterV = GetSizeFromInstr(LaterI);
Value *EarlierV = GetSizeFromInstr(EarlierI);
if (LaterV && LaterV == EarlierV && AA.isMustAlias(Earlier, Later))
return OW_Complete;
const auto *LaterMemI = dyn_cast<MemIntrinsic>(LaterI);
const auto *EarlierMemI = dyn_cast<MemIntrinsic>(EarlierI);
if (LaterMemI && EarlierMemI) {
const Value *LaterV = LaterMemI->getLength();
const Value *EarlierV = EarlierMemI->getLength();
if (LaterV == EarlierV && AA.isMustAlias(Earlier, Later))
return OW_Complete;
}

// Masked stores have imprecise locations, but we can reason about them
// to some extent.
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150 changes: 150 additions & 0 deletions llvm/test/Transforms/DeadStoreElimination/memory-intrinsics-sizes.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -199,5 +199,155 @@ define void @memcpy_and_memset_different_size_values_3(i8* noalias %src, i8* noa
ret void
}

define void @memmove_equal_size_values(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memmove_equal_size_values(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
ret void
}

define void @memmove_different_size_values_1(i8* noalias %src, i8* noalias %dst, i64 %len.1, i64 %len.2) {
; CHECK-LABEL: @memmove_different_size_values_1(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC]], i64 [[LEN_2:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len.1, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len.2, i1 false)
ret void
}

define void @memmove_different_size_values_2(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memmove_different_size_values_2(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC]], i64 100, i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 100, i1 false)
ret void
}

define void @memmove_different_size_values_3(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memmove_different_size_values_3(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 100, i1 false)
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC]], i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 100, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
ret void
}

define void @memset_and_memmove_equal_size_values(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memset_and_memmove_equal_size_values(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 %len, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
ret void
}

define void @memset_and_memmove_different_size_values_1(i8* noalias %src, i8* noalias %dst, i64 %len.1, i64 %len.2) {
; CHECK-LABEL: @memset_and_memmove_different_size_values_1(
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST:%.*]], i8 0, i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC:%.*]], i64 [[LEN_2:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 %len.1, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len.2, i1 false)
ret void
}

define void @memset_and_memmove_different_size_values_2(i8* noalias %src, i8* noalias %dst, i64 %len.1) {
; CHECK-LABEL: @memset_and_memmove_different_size_values_2(
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST:%.*]], i8 0, i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC:%.*]], i64 100, i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 %len.1, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 100, i1 false)
ret void
}

define void @memset_and_memmove_different_size_values_3(i8* noalias %src, i8* noalias %dst, i64 %len.1) {
; CHECK-LABEL: @memset_and_memmove_different_size_values_3(
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST:%.*]], i8 0, i64 100, i1 false)
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST]], i8* [[SRC:%.*]], i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 100, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len.1, i1 false)
ret void
}

define void @memmove_and_memset_equal_size_values(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memmove_and_memset_equal_size_values(
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST:%.*]], i8 0, i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 %len, i1 false)
ret void
}

define void @memmove_and_memset_different_size_values_1(i8* noalias %src, i8* noalias %dst, i64 %len.1, i64 %len.2) {
; CHECK-LABEL: @memmove_and_memset_different_size_values_1(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST]], i8 0, i64 [[LEN_2:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len.1, i1 false)
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 %len.2, i1 false)
ret void
}

define void @memmove_and_memset_different_size_values_2(i8* noalias %src, i8* noalias %dst, i64 %len.1) {
; CHECK-LABEL: @memmove_and_memset_different_size_values_2(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST]], i8 0, i64 100, i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len.1, i1 false)
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 100, i1 false)
ret void
}

define void @memmove_and_memset_different_size_values_3(i8* noalias %src, i8* noalias %dst, i64 %len.1) {
; CHECK-LABEL: @memmove_and_memset_different_size_values_3(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 100, i1 false)
; CHECK-NEXT: call void @llvm.memset.p0i8.i64(i8* align 1 [[DST]], i8 0, i64 [[LEN_1:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 100, i1 false)
call void @llvm.memset.p0i8.i64(i8* align 1 %dst, i8 0, i64 %len.1, i1 false)
ret void
}

define void @memmove_and_memcpy_equal_size_values(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memmove_and_memcpy_equal_size_values(
; CHECK-NEXT: call void @llvm.memcpy.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
ret void
}

define void @memcpy_and_memmove_equal_size_values(i8* noalias %src, i8* noalias %dst, i64 %len) {
; CHECK-LABEL: @memcpy_and_memmove_equal_size_values(
; CHECK-NEXT: call void @llvm.memmove.p0i8.p0i8.i64(i8* [[DST:%.*]], i8* [[SRC:%.*]], i64 [[LEN:%.*]], i1 false)
; CHECK-NEXT: ret void
;
call void @llvm.memcpy.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
call void @llvm.memmove.p0i8.p0i8.i64(i8* %dst, i8* %src, i64 %len, i1 false)
ret void
}

declare void @llvm.memset.p0i8.i64(i8* nocapture writeonly, i8, i64, i1 immarg)
declare void @llvm.memcpy.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i1)
declare void @llvm.memmove.p0i8.p0i8.i64(i8* nocapture, i8* nocapture, i64, i1)

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