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| author | David Majnemer <david.majnemer@gmail.com> | 2014-08-22 07:56:32 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2014-08-22 07:56:32 +0000 |
| commit | 42b83a5e3643c049eb4f89e9ca07de245d2979ea (patch) | |
| tree | 342f3edb130a939a4ffcf163bc8e970cec86a362 /llvm/test/Transforms | |
| parent | 987f1864caeb3b685e03d78c7316b97c506b649f (diff) | |
| download | bcm5719-llvm-42b83a5e3643c049eb4f89e9ca07de245d2979ea.tar.gz bcm5719-llvm-42b83a5e3643c049eb4f89e9ca07de245d2979ea.zip | |
InstCombine: Don't unconditionally preserve 'nsw' when shrinking constants
Consider:
%add = add nsw i32 %a, -16777216
%and = and i32 %add, 255
Regardless of whether or not we demand the sign bit of %add, we cannot
replace -16777216 with 2130706432 without also removing 'nsw' from the
instruction.
This fixes PR20377.
llvm-svn: 216261
Diffstat (limited to 'llvm/test/Transforms')
| -rw-r--r-- | llvm/test/Transforms/InstCombine/cast.ll | 14 |
1 files changed, 13 insertions, 1 deletions
diff --git a/llvm/test/Transforms/InstCombine/cast.ll b/llvm/test/Transforms/InstCombine/cast.ll index 86e9f3f5335..81b0d7eff52 100644 --- a/llvm/test/Transforms/InstCombine/cast.ll +++ b/llvm/test/Transforms/InstCombine/cast.ll @@ -1022,7 +1022,19 @@ define i64 @test83(i16 %a, i64 %k) { ret i64 %sh_prom1 ; CHECK-LABEL: @test83( -; CHECK: %sub = add nsw i64 %k, 4294967295 +; CHECK: %sub = add i64 %k, 4294967295 ; CHECK: %sh_prom = trunc i64 %sub to i32 ; CHECK: %shl = shl i32 %conv, %sh_prom } + +define i8 @test84(i32 %a) { + %add = add nsw i32 %a, -16777216 + %shr = lshr exact i32 %add, 23 + %trunc = trunc i32 %shr to i8 + ret i8 %trunc + +; CHECK-LABEL: @test84( +; CHECK: [[ADD:%.*]] = add i32 %a, 2130706432 +; CHECK: [[SHR:%.*]] = lshr exact i32 [[ADD]], 23 +; CHECK: [[CST:%.*]] = trunc i32 [[SHR]] to i8 +} |
