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| author | Sanjay Patel <spatel@rotateright.com> | 2017-05-09 16:24:59 +0000 |
|---|---|---|
| committer | Sanjay Patel <spatel@rotateright.com> | 2017-05-09 16:24:59 +0000 |
| commit | 6844e21f593467c640f0e14e2113bf0dfb32b1a8 (patch) | |
| tree | a0bc16140ba56e87ca046528176741727e044666 /llvm/test/Transforms | |
| parent | 125c03070edbe7ee8b4f66879a08dc80cd280584 (diff) | |
| download | bcm5719-llvm-6844e21f593467c640f0e14e2113bf0dfb32b1a8.tar.gz bcm5719-llvm-6844e21f593467c640f0e14e2113bf0dfb32b1a8.zip | |
[InstCombineCasts] Fix checks in sext->lshr->trunc pattern.
The comment says to avoid the case where zero bits are shifted into the truncated value,
but the code checks that the shift is smaller than the truncated value instead of the
number of bits added by the sign extension. Fixing this allows a shift by more than the
value size to be introduced, which is undefined behavior, so the shift is capped at the
value size minus one, which has the expected behavior of filling the value with the sign
bit.
Patch by Jacob Young!
Differential Revision: https://reviews.llvm.org/D32285
llvm-svn: 302548
Diffstat (limited to 'llvm/test/Transforms')
| -rw-r--r-- | llvm/test/Transforms/InstCombine/cast.ll | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/llvm/test/Transforms/InstCombine/cast.ll b/llvm/test/Transforms/InstCombine/cast.ll index 0a1f73e7dec..a4375a5cd57 100644 --- a/llvm/test/Transforms/InstCombine/cast.ll +++ b/llvm/test/Transforms/InstCombine/cast.ll @@ -1436,8 +1436,10 @@ define <2 x i32> @test90() { ; Do not optimize to ashr i64 (shift by 48 > 96 - 64) define i64 @test91(i64 %A) { ; CHECK-LABEL: @test91( -; CHECK-NEXT: [[C:%.*]] = ashr i64 %A, 48 -; CHECK-NEXT: ret i64 [[C]] +; CHECK-NEXT: [[B:%.*]] = sext i64 %A to i96 +; CHECK-NEXT: [[C:%.*]] = lshr i96 [[B]], 48 +; CHECK-NEXT: [[D:%.*]] = trunc i96 [[C]] to i64 +; CHECK-NEXT: ret i64 [[D]] ; %B = sext i64 %A to i96 %C = lshr i96 %B, 48 @@ -1460,10 +1462,8 @@ define i64 @test92(i64 %A) { ; When optimizing to ashr i32, don't shift by more than 31. define i32 @test93(i32 %A) { ; CHECK-LABEL: @test93( -; CHECK-NEXT: [[B:%.*]] = sext i32 %A to i96 -; CHECK-NEXT: [[C:%.*]] = lshr i96 [[B]], 64 -; CHECK-NEXT: [[D:%.*]] = trunc i96 [[C]] to i32 -; CHECK-NEXT: ret i32 [[D]] +; CHECK-NEXT: [[C:%.*]] = ashr i32 %A, 31 +; CHECK-NEXT: ret i32 [[C]] ; %B = sext i32 %A to i96 %C = lshr i96 %B, 64 |
