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| author | Benjamin Kramer <benny.kra@googlemail.com> | 2011-04-30 18:16:00 +0000 |
|---|---|---|
| committer | Benjamin Kramer <benny.kra@googlemail.com> | 2011-04-30 18:16:00 +0000 |
| commit | 23b02cd0315625d9d586118abcc972053298d50b (patch) | |
| tree | 5d9d5f6566ad26fd5ed58d7f5ee195ee14eb122d | |
| parent | 2f8e038b35c06cd130b327433e40d343e1d27244 (diff) | |
Use SimplifyDemandedBits on div instructions.
This folds away silly stuff like (a&255)/1000 -> 0.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@130614 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Transforms/InstCombine/InstCombineMulDivRem.cpp | 4 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/div.ll | 7 |
2 files changed, 11 insertions, 0 deletions
diff --git a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp index 6651387481..b4f4da6fb0 100644 --- a/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp +++ b/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp @@ -320,6 +320,10 @@ Instruction *InstCombiner::commonIDivTransforms(BinaryOperator &I) { } } + // See if we can fold away this div instruction. + if (SimplifyDemandedInstructionBits(I)) + return &I; + // (X - (X rem Y)) / Y -> X / Y; usually originates as ((X / Y) * Y) / Y Value *X = 0, *Z = 0; if (match(Op0, m_Sub(m_Value(X), m_Value(Z)))) { // (X - Z) / Y; Y = Op1 diff --git a/test/Transforms/InstCombine/div.ll b/test/Transforms/InstCombine/div.ll index 7ef640b420..2e24f19dce 100644 --- a/test/Transforms/InstCombine/div.ll +++ b/test/Transforms/InstCombine/div.ll @@ -111,3 +111,10 @@ define i32 @test13(i32 %x) nounwind { ; CHECK-NEXT: ret i32 1 } +define i32 @test14(i8 %x) nounwind { + %zext = zext i8 %x to i32 + %div = udiv i32 %zext, 257 ; 0 + ret i32 %div +; CHECK: @test14 +; CHECK-NEXT: ret i32 0 +} |