From c0404b3715151d020dda074740bbdaa794f9328a Mon Sep 17 00:00:00 2001 From: Chris Lattner Date: Tue, 19 Jan 2010 18:16:19 +0000 Subject: [PATCH] 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 --- .../InstCombine/InstCombineAndOrXor.cpp | 5 +++ test/Transforms/InstCombine/idioms.ll | 32 +++++++++++++++++++ test/Transforms/InstCombine/xor2.ll | 10 ++++++ 3 files changed, 47 insertions(+) create mode 100644 test/Transforms/InstCombine/idioms.ll diff --git a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp index af300fc3577..fa7bb12ff21 100644 --- a/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp +++ b/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp @@ -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)); } } } diff --git a/test/Transforms/InstCombine/idioms.ll b/test/Transforms/InstCombine/idioms.ll new file mode 100644 index 00000000000..6b3567fc6e8 --- /dev/null +++ b/test/Transforms/InstCombine/idioms.ll @@ -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 +} diff --git a/test/Transforms/InstCombine/xor2.ll b/test/Transforms/InstCombine/xor2.ll index 23a99158137..de3d65dd8cb 100644 --- a/test/Transforms/InstCombine/xor2.ll +++ b/test/Transforms/InstCombine/xor2.ll @@ -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 +}