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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
This commit is contained in:
Chris Lattner 2010-01-19 18:16:19 +00:00
parent 9201b10daa
commit c0404b3715
3 changed files with 47 additions and 0 deletions
lib/Transforms/InstCombine
test/Transforms/InstCombine

View File

@ -1751,6 +1751,11 @@ Instruction *InstCombiner::visitXor(BinaryOperator &I) {
return BinaryOperator::CreateOr(NotX, NotY);
return BinaryOperator::CreateAnd(NotX, NotY);
}
} else if (Op0I->getOpcode() == Instruction::AShr) {
// ~(~X >>s Y) --> (X >>s Y)
if (Value *Op0NotVal = dyn_castNotVal(Op0I->getOperand(0)))
return BinaryOperator::CreateAShr(Op0NotVal, Op0I->getOperand(1));
}
}
}

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@ -0,0 +1,32 @@
; RUN: opt -instcombine %s -S | FileCheck %s
; Check that code corresponding to the following C function is
; simplified into a single ASR operation:
;
; int test_asr(int a, int b) {
; return a < 0 ? -(-a - 1 >> b) - 1 : a >> b;
; }
;
define i32 @test_asr(i32 %a, i32 %b) {
entry:
%c = icmp slt i32 %a, 0
br i1 %c, label %bb2, label %bb3
bb2:
%t1 = sub i32 0, %a
%not = sub i32 %t1, 1
%d = ashr i32 %not, %b
%t2 = sub i32 0, %d
%not2 = sub i32 %t2, 1
br label %bb4
bb3:
%e = ashr i32 %a, %b
br label %bb4
bb4:
%f = phi i32 [ %not2, %bb2 ], [ %e, %bb3 ]
ret i32 %f
; CHECK: @test_asr
; CHECK: bb4:
; CHECK: %f = ashr i32 %a, %b
; CHECK: ret i32 %f
}

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@ -41,3 +41,13 @@ define i32 @test3(i32 %tmp1) {
%ov110 = xor i32 %ov31, 153
ret i32 %ov110
}
define i32 @test4(i32 %A, i32 %B) {
%1 = xor i32 %A, -1
%2 = ashr i32 %1, %B
%3 = xor i32 %2, -1
ret i32 %3
; CHECK: @test4
; CHECK: %1 = ashr i32 %A, %B
; CHECK: ret i32 %1
}