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optimize ~(~X >>s Y) --> (X >>s Y), patch by Edmund Grimley
Evans! git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@93884 91177308-0d34-0410-b5e6-96231b3b80d8
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@ -1751,6 +1751,11 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
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return BinaryOperator::CreateOr(NotX, NotY);
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return BinaryOperator::CreateAnd(NotX, NotY);
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}
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} else if (Op0I->getOpcode() == Instruction::AShr) {
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// ~(~X >>s Y) --> (X >>s Y)
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if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0)))
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return BinaryOperator::CreateAShr(Op0NotVal, Op0I->getOperand(1));
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}
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}
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}
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32
test/Transforms/InstCombine/idioms.ll
Normal file
32
test/Transforms/InstCombine/idioms.ll
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@ -0,0 +1,32 @@
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; RUN: opt -instcombine %s -S | FileCheck %s
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; Check that code corresponding to the following C function is
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; simplified into a single ASR operation:
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;
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; int test_asr(int a, int b) {
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; return a < 0 ? -(-a - 1 >> b) - 1 : a >> b;
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; }
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;
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define i32 @test_asr(i32 %a, i32 %b) {
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entry:
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%c = icmp slt i32 %a, 0
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br i1 %c, label %bb2, label %bb3
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bb2:
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%t1 = sub i32 0, %a
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%not = sub i32 %t1, 1
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%d = ashr i32 %not, %b
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%t2 = sub i32 0, %d
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%not2 = sub i32 %t2, 1
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br label %bb4
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bb3:
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%e = ashr i32 %a, %b
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br label %bb4
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bb4:
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%f = phi i32 [ %not2, %bb2 ], [ %e, %bb3 ]
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ret i32 %f
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; CHECK: @test_asr
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; CHECK: bb4:
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; CHECK: %f = ashr i32 %a, %b
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; CHECK: ret i32 %f
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}
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@ -41,3 +41,13 @@ define i32 @test3(i32 %tmp1) {
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%ov110 = xor i32 %ov31, 153
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ret i32 %ov110
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}
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define i32 @test4(i32 %A, i32 %B) {
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%1 = xor i32 %A, -1
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%2 = ashr i32 %1, %B
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%3 = xor i32 %2, -1
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ret i32 %3
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; CHECK: @test4
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; CHECK: %1 = ashr i32 %A, %B
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; CHECK: ret i32 %1
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}
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