From 53fc39992df9c485ea45f28998c1ef99caed63f9 Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Mon, 8 Jul 2013 11:53:08 +0000 Subject: [PATCH] InstCombine: Fold X-C1 (X & -2) == C1 Back in r179493 we determined that two transforms collided with each other. The fix back then was to reorder the transforms so that the preferred transform would give it a try and then we would try the secondary transform. However, it was noted that the best approach would canonicalize one transform into the other, removing the collision and allowing us to optimize IR given to us in that form. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185808 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/InstCombine/InstCombineCompares.cpp | 8 ++++++++ test/Transforms/InstCombine/icmp.ll | 10 ++++++++++ 2 files changed, 18 insertions(+) diff --git a/lib/Transforms/InstCombine/InstCombineCompares.cpp b/lib/Transforms/InstCombine/InstCombineCompares.cpp index 0f1576050ff..f4734461a62 100644 --- a/lib/Transforms/InstCombine/InstCombineCompares.cpp +++ b/lib/Transforms/InstCombine/InstCombineCompares.cpp @@ -1539,6 +1539,14 @@ Instruction *InstCombiner::visitICmpInstWithInstAndIntCst(ICmpInst &ICI, Builder->getInt(CR.getLower())); } } + + // X-C1 (X & -2) == C1 + // iff C1 & 1 == 0 + if (ICI.getPredicate() == ICmpInst::ICMP_ULT && LHSI->hasOneUse() && + LHSV[0] == 0 && RHSV == 2) + return new ICmpInst(ICmpInst::ICMP_EQ, + Builder->CreateAnd(LHSI->getOperand(0), -RHSV), + ConstantExpr::getNeg(LHSC)); } break; } diff --git a/test/Transforms/InstCombine/icmp.ll b/test/Transforms/InstCombine/icmp.ll index 929688195fe..cf8305df2a9 100644 --- a/test/Transforms/InstCombine/icmp.ll +++ b/test/Transforms/InstCombine/icmp.ll @@ -1113,3 +1113,13 @@ define i1 @or_icmp_eq_B_0_icmp_ult_A_B(i64 %a, i64 %b) { %3 = or i1 %1, %2 ret i1 %3 } + +; CHECK: @icmp_add_ult_2 +; CHECK-NEXT: [[AND:%[a-z0-9]+]] = and i32 %X, -2 +; CHECK-NEXT: [[CMP:%[a-z0-9]+]] = icmp eq i32 [[AND]], 14 +; CHECK-NEXT: ret i1 [[CMP]] +define i1 @icmp_add_ult_2(i32 %X) { + %add = add i32 %X, -14 + %cmp = icmp ult i32 %add, 2 + ret i1 %cmp +} -- 2.34.1