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| author | Nikita Popov <nikita.ppv@gmail.com> | 2019-02-28 08:11:20 +0000 |
|---|---|---|
| committer | Nikita Popov <nikita.ppv@gmail.com> | 2019-02-28 08:11:20 +0000 |
| commit | 6c57395fb438881018e0897f09f2137dc8dbd111 (patch) | |
| tree | 35f8da1b04f4e77d6e0271036c0f69911566b212 /llvm/test/Transforms/InstCombine/saturating-add-sub.ll | |
| parent | 6ca7398a1e9481c950d60f2200b297fd9c2d67a7 (diff) | |
| download | bcm5719-llvm-6c57395fb438881018e0897f09f2137dc8dbd111.tar.gz bcm5719-llvm-6c57395fb438881018e0897f09f2137dc8dbd111.zip | |
[ValueTracking] More accurate unsigned add overflow detection
Part of D58593.
Compute precise overflow conditions based on all known bits, rather
than just the sign bits. Unsigned a + b overflows iff a > ~b, and we
can determine whether this always/never happens based on the minimal
and maximal values achievable for a and ~b subject to the known bits
constraint.
llvm-svn: 355072
Diffstat (limited to 'llvm/test/Transforms/InstCombine/saturating-add-sub.ll')
| -rw-r--r-- | llvm/test/Transforms/InstCombine/saturating-add-sub.ll | 12 |
1 files changed, 4 insertions, 8 deletions
diff --git a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll index 6f616bfe1ee..aa833f7c728 100644 --- a/llvm/test/Transforms/InstCombine/saturating-add-sub.ll +++ b/llvm/test/Transforms/InstCombine/saturating-add-sub.ll @@ -233,7 +233,7 @@ define <2 x i8> @test_vector_uadd_neg_nneg(<2 x i8> %a) { define i8 @test_scalar_uadd_never_overflows(i8 %a) { ; CHECK-LABEL: @test_scalar_uadd_never_overflows( ; CHECK-NEXT: [[A_MASKED:%.*]] = and i8 [[A:%.*]], -127 -; CHECK-NEXT: [[R:%.*]] = call i8 @llvm.uadd.sat.i8(i8 [[A_MASKED]], i8 1) +; CHECK-NEXT: [[R:%.*]] = add nuw nsw i8 [[A_MASKED]], 1 ; CHECK-NEXT: ret i8 [[R]] ; %a_masked = and i8 %a, 129 @@ -244,7 +244,7 @@ define i8 @test_scalar_uadd_never_overflows(i8 %a) { define <2 x i8> @test_vector_uadd_never_overflows(<2 x i8> %a) { ; CHECK-LABEL: @test_vector_uadd_never_overflows( ; CHECK-NEXT: [[A_MASKED:%.*]] = and <2 x i8> [[A:%.*]], <i8 -127, i8 -127> -; CHECK-NEXT: [[R:%.*]] = call <2 x i8> @llvm.uadd.sat.v2i8(<2 x i8> [[A_MASKED]], <2 x i8> <i8 1, i8 1>) +; CHECK-NEXT: [[R:%.*]] = add nuw nsw <2 x i8> [[A_MASKED]], <i8 1, i8 1> ; CHECK-NEXT: ret <2 x i8> [[R]] ; %a_masked = and <2 x i8> %a, <i8 129, i8 129> @@ -254,9 +254,7 @@ define <2 x i8> @test_vector_uadd_never_overflows(<2 x i8> %a) { define i8 @test_scalar_uadd_always_overflows(i8 %a) { ; CHECK-LABEL: @test_scalar_uadd_always_overflows( -; CHECK-NEXT: [[A_MASKED:%.*]] = or i8 [[A:%.*]], -64 -; CHECK-NEXT: [[R:%.*]] = call i8 @llvm.uadd.sat.i8(i8 [[A_MASKED]], i8 64) -; CHECK-NEXT: ret i8 [[R]] +; CHECK-NEXT: ret i8 -1 ; %a_masked = or i8 %a, 192 %r = call i8 @llvm.uadd.sat.i8(i8 %a_masked, i8 64) @@ -265,9 +263,7 @@ define i8 @test_scalar_uadd_always_overflows(i8 %a) { define <2 x i8> @test_vector_uadd_always_overflows(<2 x i8> %a) { ; CHECK-LABEL: @test_vector_uadd_always_overflows( -; CHECK-NEXT: [[A_MASKED:%.*]] = or <2 x i8> [[A:%.*]], <i8 -64, i8 -64> -; CHECK-NEXT: [[R:%.*]] = call <2 x i8> @llvm.uadd.sat.v2i8(<2 x i8> [[A_MASKED]], <2 x i8> <i8 64, i8 64>) -; CHECK-NEXT: ret <2 x i8> [[R]] +; CHECK-NEXT: ret <2 x i8> <i8 -1, i8 -1> ; %a_masked = or <2 x i8> %a, <i8 192, i8 192> %r = call <2 x i8> @llvm.uadd.sat.v2i8(<2 x i8> %a_masked, <2 x i8> <i8 64, i8 64>) |
