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Teach MemoryBuiltins and InstructionSimplify that operator new never returns NULL.

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This is safe per C++11 18.6.1.1p3: [operator new returns] a non-null pointer to
suitably aligned storage (3.7.4), or else throw a bad_alloc exception. This
requirement is binding on a replacement version of this function.

Brings us a tiny bit closer to eliminating more vector push_backs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@191310 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2013-09-24 16:37:51 +00:00
parent d721520e4c
commit 6629210aaf
6 changed files with 46 additions and 7 deletions
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8
lib/Analysis/ValueTracking.cpp
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@ -15,6 +15,7 @@
#include "llvm/Analysis/ValueTracking.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/Analysis/InstructionSimplify.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/GlobalAlias.h"
@ -2064,7 +2065,7 @@ bool llvm::isSafeToSpeculativelyExecute(const Value *V,
/// isKnownNonNull - Return true if we know that the specified value is never
/// null.
bool llvm::isKnownNonNull(const Value *V) {
bool llvm::isKnownNonNull(const Value *V, const TargetLibraryInfo *TLI) {
// Alloca never returns null, malloc might.
if (isa<AllocaInst>(V)) return true;
@ -2075,5 +2076,10 @@ bool llvm::isKnownNonNull(const Value *V) {
// Global values are not null unless extern weak.
if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
return !GV->hasExternalWeakLinkage();
// operator new never returns null.
if (isOperatorNewLikeFn(V, TLI, /*LookThroughBitCast=*/true))
return true;
return false;
}