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[DSE] Fix bug in partial overwrite tracking

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Summary:
Found cases where DSE incorrectly add partially-overwritten intervals.
Please see the test case for details.

Reviewers: mcrosier, eeckstein, hfinkel

Subscribers: mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D21859

llvm-svn: 274237
This commit is contained in:
Jun Bum Lim 2016-06-30 15:32:20 +00:00
parent 437bb9ba7e
commit 78c02c3c2f
2 changed files with 53 additions and 7 deletions
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21
lib/Transforms/Scalar/DeadStoreElimination.cpp
View File

@ -385,18 +385,25 @@ static OverwriteResult isOverwrite(const MemoryLocation &Later,
// Find any intervals ending at, or after, LaterIntStart which start
// before LaterIntEnd.
auto ILI = IM.lower_bound(LaterIntStart);
if (ILI != IM.end() && ILI->second < LaterIntEnd) {
// This existing interval ends in the middle of
// [LaterIntStart, LaterIntEnd), erase it adjusting our start.
if (ILI != IM.end() && ILI->second <= LaterIntEnd) {
// This existing interval is overlapped with the current store somewhere
// in [LaterIntStart, LaterIntEnd]. Merge them by erasing the existing
// intervals and adjusting our start and end.
LaterIntStart = std::min(LaterIntStart, ILI->second);
LaterIntEnd = std::max(LaterIntEnd, ILI->first);
ILI = IM.erase(ILI);
while (ILI != IM.end() && ILI->first <= LaterIntEnd)
ILI = IM.erase(ILI);
if (ILI != IM.end() && ILI->second < LaterIntEnd)
// Continue erasing and adjusting our end in case other previous
// intervals are also overlapped with the current store.
//
// |--- ealier 1 ---| |--- ealier 2 ---|
// |------- later---------|
//
while (ILI != IM.end() && ILI->second <= LaterIntEnd) {
assert(ILI->second > LaterIntStart && "Unexpected interval");
LaterIntEnd = std::max(LaterIntEnd, ILI->first);
ILI = IM.erase(ILI);
}
}
IM[LaterIntEnd] = LaterIntStart;

39
test/Transforms/DeadStoreElimination/combined-partial-overwrites.ll
View File

@ -198,3 +198,42 @@ entry:
ret i8 0
}
define signext i8 @test6(i32 *%ptr) {
entry:
; CHECK-LABEL: @test6
store i32 0, i32* %ptr
%bptr = bitcast i32* %ptr to i16*
%bptr1 = getelementptr inbounds i16, i16* %bptr, i64 0
%bptr2 = getelementptr inbounds i16, i16* %bptr, i64 1
store i16 1456, i16* %bptr2, align 1
store i16 65535, i16* %bptr1, align 1
; CHECK-NOT: store i32 0, i32* %ptr
ret i8 0
}
define signext i8 @test7(i64 *%ptr) {
entry:
; CHECK-LABEL: @test7
store i64 0, i64* %ptr
%bptr = bitcast i64* %ptr to i16*
%bptr1 = getelementptr inbounds i16, i16* %bptr, i64 0
%bptr2 = getelementptr inbounds i16, i16* %bptr, i64 1
%bptr3 = getelementptr inbounds i16, i16* %bptr, i64 2
%bptr4 = getelementptr inbounds i16, i16* %bptr, i64 3
store i16 1346, i16* %bptr1, align 1
store i16 1756, i16* %bptr3, align 1
store i16 1456, i16* %bptr2, align 1
store i16 5656, i16* %bptr4, align 1
; CHECK-NOT: store i64 0, i64* %ptr
ret i8 0
}