From 7a2ed26563512149ea03e56d8ecd92c884c32f8f Mon Sep 17 00:00:00 2001 From: David Majnemer Date: Fri, 16 May 2014 16:57:04 +0000 Subject: [PATCH] InstSimplify: Optimize using dividend in sdiv Summary: The dividend in an sdiv tells us the largest and smallest possible results. Use this fact to optimize comparisons against an sdiv with a constant dividend. Reviewers: nicholas Subscribers: llvm-commits Differential Revision: http://reviews.llvm.org/D3795 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@208999 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/InstructionSimplify.cpp | 4 ++++ test/Transforms/InstSimplify/compare.ll | 9 +++++++++ 2 files changed, 13 insertions(+) diff --git a/lib/Analysis/InstructionSimplify.cpp b/lib/Analysis/InstructionSimplify.cpp index 5421a399226..4cad81b1398 100644 --- a/lib/Analysis/InstructionSimplify.cpp +++ b/lib/Analysis/InstructionSimplify.cpp @@ -2020,6 +2020,10 @@ static Value *SimplifyICmpInst(unsigned Predicate, Value *LHS, Value *RHS, APInt NegOne = APInt::getAllOnesValue(Width); if (!CI2->isZero()) Upper = NegOne.udiv(CI2->getValue()) + 1; + } else if (match(LHS, m_SDiv(m_ConstantInt(CI2), m_Value()))) { + // 'sdiv CI2, x' produces [-|CI2|, |CI2|]. + Upper = CI2->getValue().abs() + 1; + Lower = (-Upper) + 1; } else if (match(LHS, m_SDiv(m_Value(), m_ConstantInt(CI2)))) { // 'sdiv x, CI2' produces [INT_MIN / CI2, INT_MAX / CI2]. APInt IntMin = APInt::getSignedMinValue(Width); diff --git a/test/Transforms/InstSimplify/compare.ll b/test/Transforms/InstSimplify/compare.ll index 76cff902c96..0e270bbe0f9 100644 --- a/test/Transforms/InstSimplify/compare.ll +++ b/test/Transforms/InstSimplify/compare.ll @@ -817,3 +817,12 @@ define i1 @compare_always_false_ne(i16 %a) { ; CHECK-LABEL: @compare_always_false_ne ; CHECK-NEXT: ret i1 true } + +define i1 @compare_dividend(i32 %a) { + %div = sdiv i32 2, %a + %cmp = icmp eq i32 %div, 3 + ret i1 %cmp + +; CHECK-LABEL: @compare_dividend +; CHECK-NEXT: ret i1 false +} -- 2.34.1