From fa9f4208faa513c7b67ca3a75b785502c621aa07 Mon Sep 17 00:00:00 2001 From: Johannes Doerfert Date: Fri, 16 Aug 2019 21:53:49 +0000 Subject: [PATCH] [CaptureTracking] Allow null to be in either icmp operand Summary: Before we required the comparison against null to be "canonical", hence null to be operand #1. This patch allows null to be in either operand, similar to the handling of loaded globals that follows. Reviewers: sanjoy, hfinkel, aykevl, sstefan1, uenoku Subscribers: hiraditya, bollu, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D66321 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@369158 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Analysis/CaptureTracking.cpp | 12 +++++++----- test/Transforms/FunctionAttrs/nocapture.ll | 14 ++++++++++++++ 2 files changed, 21 insertions(+), 5 deletions(-) diff --git a/lib/Analysis/CaptureTracking.cpp b/lib/Analysis/CaptureTracking.cpp index f12e50e6c92..fe551bdfe18 100644 --- a/lib/Analysis/CaptureTracking.cpp +++ b/lib/Analysis/CaptureTracking.cpp @@ -331,7 +331,9 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker, AddUses(I); break; case Instruction::ICmp: { - if (auto *CPN = dyn_cast(I->getOperand(1))) { + unsigned Idx = (I->getOperand(0) == V) ? 0 : 1; + unsigned OtherIdx = 1 - Idx; + if (auto *CPN = dyn_cast(I->getOperand(OtherIdx))) { // Don't count comparisons of a no-alias return value against null as // captures. This allows us to ignore comparisons of malloc results // with null, for example. @@ -339,7 +341,7 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker, if (isNoAliasCall(V->stripPointerCasts())) break; if (!I->getFunction()->nullPointerIsDefined()) { - auto *O = I->getOperand(0)->stripPointerCastsSameRepresentation(); + auto *O = I->getOperand(Idx)->stripPointerCastsSameRepresentation(); // An inbounds GEP can either be a valid pointer (pointing into // or to the end of an allocation), or be null in the default // address space. So for an inbounds GEPs there is no way to let @@ -353,15 +355,15 @@ void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker, // cannot lead to pointer escapes, because if it is not null it // must be a valid (in-bounds) pointer. bool CanBeNull; - if (O->getPointerDereferenceableBytes(I->getModule()->getDataLayout(), CanBeNull)) + if (O->getPointerDereferenceableBytes(I->getModule()->getDataLayout(), + CanBeNull)) break; } } // Comparison against value stored in global variable. Given the pointer // does not escape, its value cannot be guessed and stored separately in a // global variable. - unsigned OtherIndex = (I->getOperand(0) == V) ? 1 : 0; - auto *LI = dyn_cast(I->getOperand(OtherIndex)); + auto *LI = dyn_cast(I->getOperand(OtherIdx)); if (LI && isa(LI->getPointerOperand())) break; // Otherwise, be conservative. There are crazy ways to capture pointers diff --git a/test/Transforms/FunctionAttrs/nocapture.ll b/test/Transforms/FunctionAttrs/nocapture.ll index b109249674b..b580cdcea7e 100644 --- a/test/Transforms/FunctionAttrs/nocapture.ll +++ b/test/Transforms/FunctionAttrs/nocapture.ll @@ -259,6 +259,12 @@ define i1 @captureICmp(i32* %x) { ret i1 %1 } +; CHECK: define i1 @captureICmpRev(i32* readnone %x) +define i1 @captureICmpRev(i32* %x) { + %1 = icmp eq i32* null, %x + ret i1 %1 +} + ; CHECK: define i1 @nocaptureInboundsGEPICmp(i32* nocapture readnone %x) define i1 @nocaptureInboundsGEPICmp(i32* %x) { %1 = getelementptr inbounds i32, i32* %x, i32 5 @@ -267,6 +273,14 @@ define i1 @nocaptureInboundsGEPICmp(i32* %x) { ret i1 %3 } +; CHECK: define i1 @nocaptureInboundsGEPICmpRev(i32* nocapture readnone %x) +define i1 @nocaptureInboundsGEPICmpRev(i32* %x) { + %1 = getelementptr inbounds i32, i32* %x, i32 5 + %2 = bitcast i32* %1 to i8* + %3 = icmp eq i8* null, %2 + ret i1 %3 +} + ; CHECK: define i1 @nocaptureDereferenceableOrNullICmp(i32* nocapture readnone dereferenceable_or_null(4) %x) define i1 @nocaptureDereferenceableOrNullICmp(i32* dereferenceable_or_null(4) %x) { %1 = bitcast i32* %x to i8* -- 2.49.0