From 011cb4d5bdc3a56e9d8e7a19c1a576a3eaabe5ad Mon Sep 17 00:00:00 2001 From: Nick Lewycky Date: Fri, 13 Mar 2015 01:37:52 +0000 Subject: [PATCH] When forming an addrec out of a phi don't just look at the last computation and steal its flags for our own, there may be other computations in the middle. Check whether the LHS of the computation is the phi itself and then we know it's safe to steal the flags. Fixes PR22795. There's a missed optimization opportunity where we could look at the full chain of computation and take the intersection of the flags instead of only looking one instruction deep. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232134 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/ScalarEvolution.cpp | 12 ++-- test/Analysis/ScalarEvolution/trip-count.ll | 64 ++++++++++++++++++++- 2 files changed, 70 insertions(+), 6 deletions(-) diff --git a/lib/Analysis/ScalarEvolution.cpp b/lib/Analysis/ScalarEvolution.cpp index dcff7b60fb7..dfef7296848 100644 --- a/lib/Analysis/ScalarEvolution.cpp +++ b/lib/Analysis/ScalarEvolution.cpp @@ -3591,10 +3591,12 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) { // If the increment doesn't overflow, then neither the addrec nor // the post-increment will overflow. if (const AddOperator *OBO = dyn_cast(BEValueV)) { - if (OBO->hasNoUnsignedWrap()) - Flags = setFlags(Flags, SCEV::FlagNUW); - if (OBO->hasNoSignedWrap()) - Flags = setFlags(Flags, SCEV::FlagNSW); + if (OBO->getOperand(0) == PN) { + if (OBO->hasNoUnsignedWrap()) + Flags = setFlags(Flags, SCEV::FlagNUW); + if (OBO->hasNoSignedWrap()) + Flags = setFlags(Flags, SCEV::FlagNSW); + } } else if (GEPOperator *GEP = dyn_cast(BEValueV)) { // If the increment is an inbounds GEP, then we know the address // space cannot be wrapped around. We cannot make any guarantee @@ -3602,7 +3604,7 @@ const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) { // unsigned but we may have a negative index from the base // pointer. We can guarantee that no unsigned wrap occurs if the // indices form a positive value. - if (GEP->isInBounds()) { + if (GEP->isInBounds() && GEP->getOperand(0) == PN) { Flags = setFlags(Flags, SCEV::FlagNW); const SCEV *Ptr = getSCEV(GEP->getPointerOperand()); diff --git a/test/Analysis/ScalarEvolution/trip-count.ll b/test/Analysis/ScalarEvolution/trip-count.ll index f705be60fad..1b75c88c753 100644 --- a/test/Analysis/ScalarEvolution/trip-count.ll +++ b/test/Analysis/ScalarEvolution/trip-count.ll @@ -1,11 +1,15 @@ ; RUN: opt < %s -analyze -scalar-evolution -scalar-evolution-max-iterations=0 | FileCheck %s ; PR1101 +target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128" +target triple = "x86_64-unknown-linux-gnu" + @A = weak global [1000 x i32] zeroinitializer, align 32 +; CHECK: Printing analysis 'Scalar Evolution Analysis' for function 'test1': ; CHECK: backedge-taken count is 10000 -define void @test(i32 %N) { +define void @test1(i32 %N) { entry: br label %bb3 @@ -26,3 +30,61 @@ bb5: ; preds = %bb3 return: ; preds = %bb5 ret void } + +; PR22795 +; CHECK: Printing analysis 'Scalar Evolution Analysis' for function 'test2': +; CHECK: %iv = phi i32 [ -1, %entry ], [ %next.1, %for.inc.1 ] +; CHECK-NEXT: --> {-1,+,2}<%preheader> U: full-set S: full-set Exits: 13 + +define i32 @test2() { +entry: + %bins = alloca [16 x i64], align 16 + %0 = bitcast [16 x i64]* %bins to i8* + call void @llvm.memset.p0i8.i64(i8* %0, i8 0, i64 128, i32 16, i1 false) + br label %preheader + +preheader: ; preds = %for.inc.1, %entry + %v11 = phi i64 [ 0, %entry ], [ %next12.1, %for.inc.1 ] + %iv = phi i32 [ -1, %entry ], [ %next.1, %for.inc.1 ] + %cmp = icmp sgt i64 %v11, 0 + br i1 %cmp, label %for.body, label %for.inc + +for.body: ; preds = %preheader + %zext = zext i32 %iv to i64 + %arrayidx = getelementptr [16 x i64], [16 x i64]* %bins, i64 0, i64 %v11 + %loaded = load i64, i64* %arrayidx, align 8 + %add = add i64 %loaded, 1 + %add2 = add i64 %add, %zext + store i64 %add2, i64* %arrayidx, align 8 + br label %for.inc + +for.inc: ; preds = %for.body, %preheader + %next12 = add nuw nsw i64 %v11, 1 + %next = add nsw i32 %iv, 1 + br i1 true, label %for.body.1, label %for.inc.1 + +end: ; preds = %for.inc.1 + %arrayidx8 = getelementptr [16 x i64], [16 x i64]* %bins, i64 0, i64 2 + %load = load i64, i64* %arrayidx8, align 16 + %shr4 = lshr i64 %load, 32 + %conv = trunc i64 %shr4 to i32 + ret i32 %conv + +for.body.1: ; preds = %for.inc + %zext.1 = zext i32 %next to i64 + %arrayidx.1 = getelementptr [16 x i64], [16 x i64]* %bins, i64 0, i64 %next12 + %loaded.1 = load i64, i64* %arrayidx.1, align 8 + %add.1 = add i64 %loaded.1, 1 + %add2.1 = add i64 %add.1, %zext.1 + store i64 %add2.1, i64* %arrayidx.1, align 8 + br label %for.inc.1 + +for.inc.1: ; preds = %for.body.1, %for.inc + %next12.1 = add nuw nsw i64 %next12, 1 + %next.1 = add nuw nsw i32 %next, 1 + %exitcond.1 = icmp eq i64 %next12.1, 16 + br i1 %exitcond.1, label %end, label %preheader +} + +; Function Attrs: nounwind +declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) #0