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| author | David Majnemer <david.majnemer@gmail.com> | 2013-07-09 22:01:22 +0000 |
|---|---|---|
| committer | David Majnemer <david.majnemer@gmail.com> | 2013-07-09 22:01:22 +0000 |
| commit | 8c5c6f0e090f91b6555cdd9d2eea238fff3befe6 (patch) | |
| tree | 8d3a93378e1e1c3c148122b14136a9c685ca9891 | |
| parent | e4e742a62d5efa8f69b351dde87f9a20c03503ef (diff) | |
| download | llvm-8c5c6f0e090f91b6555cdd9d2eea238fff3befe6.tar.gz llvm-8c5c6f0e090f91b6555cdd9d2eea238fff3befe6.tar.bz2 llvm-8c5c6f0e090f91b6555cdd9d2eea238fff3befe6.tar.xz | |
InstSimplify: X >> X -> 0
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185973 91177308-0d34-0410-b5e6-96231b3b80d8
| -rw-r--r-- | lib/Analysis/InstructionSimplify.cpp | 8 | ||||
| -rw-r--r-- | test/Transforms/InstCombine/div-shift.ll | 6 | ||||
| -rw-r--r-- | test/Transforms/InstSimplify/compare.ll | 16 |
3 files changed, 27 insertions, 3 deletions
diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp index bf7745143d..d66ecca928 100644 --- a/lib/Analysis/InstructionSimplify.cpp +++ b/lib/Analysis/InstructionSimplify.cpp @@ -1363,6 +1363,10 @@ static Value *SimplifyLShrInst(Value *Op0, Value *Op1, bool isExact, if (Value *V = SimplifyShift(Instruction::LShr, Op0, Op1, Q, MaxRecurse)) return V; + // X >> X -> 0 + if (Op0 == Op1) + return Constant::getNullValue(Op0->getType()); + // undef >>l X -> 0 if (match(Op0, m_Undef())) return Constant::getNullValue(Op0->getType()); @@ -1391,6 +1395,10 @@ static Value *SimplifyAShrInst(Value *Op0, Value *Op1, bool isExact, if (Value *V = SimplifyShift(Instruction::AShr, Op0, Op1, Q, MaxRecurse)) return V; + // X >> X -> 0 + if (Op0 == Op1) + return Constant::getNullValue(Op0->getType()); + // all ones >>a X -> all ones if (match(Op0, m_AllOnes())) return Op0; diff --git a/test/Transforms/InstCombine/div-shift.ll b/test/Transforms/InstCombine/div-shift.ll index 46d0f9afd7..3350f19405 100644 --- a/test/Transforms/InstCombine/div-shift.ll +++ b/test/Transforms/InstCombine/div-shift.ll @@ -54,9 +54,9 @@ define i32 @t5(i1 %x, i1 %y, i32 %V) nounwind { ; CHECK: t5 ; CHECK-NOT: udiv ; CHECK-NEXT: [[SEL1:%.*]] = select i1 %x, i32 5, i32 6 -; CHECK-NEXT: [[SEL2:%.*]] = select i1 %y, i32 [[SEL1]], i32 %V -; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 %V, [[SEL2]] -; CHECK-NEXT: ret i32 [[LSHR]] +; CHECK-NEXT: [[LSHR:%.*]] = lshr i32 %V, [[SEL1]] +; CHECK-NEXT: [[SEL2:%.*]] = select i1 %y, i32 [[LSHR]], i32 0 +; CHECK-NEXT: ret i32 [[SEL2]] %1 = shl i32 1, %V %2 = select i1 %x, i32 32, i32 64 %3 = select i1 %y, i32 %2, i32 %1 diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll index b764c761cf..82d56028c3 100644 --- a/test/Transforms/InstSimplify/compare.ll +++ b/test/Transforms/InstSimplify/compare.ll @@ -357,6 +357,14 @@ define i1 @lshr2(i32 %x) { ; CHECK: ret i1 false } +define i1 @lshr3(i32 %x) { +; CHECK: @lshr3 + %s = lshr i32 %x, %x + %c = icmp eq i32 %s, 0 + ret i1 %c +; CHECK: ret i1 true +} + define i1 @ashr1(i32 %x) { ; CHECK: @ashr1 %s = ashr i32 -1, %x @@ -373,6 +381,14 @@ define i1 @ashr2(i32 %x) { ; CHECK: ret i1 false } +define i1 @ashr3(i32 %x) { +; CHECK: @ashr3 + %s = ashr i32 %x, %x + %c = icmp eq i32 %s, 0 + ret i1 %c +; CHECK: ret i1 true +} + define i1 @select1(i1 %cond) { ; CHECK: @select1 %s = select i1 %cond, i32 1, i32 0 |