llvm: Add support for "-fno-delete-null-pointer-checks"
Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.
More details : https://lkml.org/lkml/2018/4/4/601
GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.
-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.
This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.
Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv
Reviewed By: efriedma, george.burgess.iv
Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits
Differential Revision: https://reviews.llvm.org/D47895
llvm-svn: 336613
diff --git a/llvm/lib/Analysis/BasicAliasAnalysis.cpp b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
index 883462a..9632634 100644
--- a/llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -85,15 +85,15 @@
// depth otherwise the algorithm in aliasGEP will assert.
static const unsigned MaxLookupSearchDepth = 6;
-bool BasicAAResult::invalidate(Function &F, const PreservedAnalyses &PA,
+bool BasicAAResult::invalidate(Function &Fn, const PreservedAnalyses &PA,
FunctionAnalysisManager::Invalidator &Inv) {
// We don't care if this analysis itself is preserved, it has no state. But
// we need to check that the analyses it depends on have been. Note that we
// may be created without handles to some analyses and in that case don't
// depend on them.
- if (Inv.invalidate<AssumptionAnalysis>(F, PA) ||
- (DT && Inv.invalidate<DominatorTreeAnalysis>(F, PA)) ||
- (LI && Inv.invalidate<LoopAnalysis>(F, PA)))
+ if (Inv.invalidate<AssumptionAnalysis>(Fn, PA) ||
+ (DT && Inv.invalidate<DominatorTreeAnalysis>(Fn, PA)) ||
+ (LI && Inv.invalidate<LoopAnalysis>(Fn, PA)))
return true;
// Otherwise this analysis result remains valid.
@@ -150,10 +150,12 @@
/// Returns the size of the object specified by V or UnknownSize if unknown.
static uint64_t getObjectSize(const Value *V, const DataLayout &DL,
const TargetLibraryInfo &TLI,
+ bool NullIsValidLoc,
bool RoundToAlign = false) {
uint64_t Size;
ObjectSizeOpts Opts;
Opts.RoundToAlign = RoundToAlign;
+ Opts.NullIsUnknownSize = NullIsValidLoc;
if (getObjectSize(V, Size, DL, &TLI, Opts))
return Size;
return MemoryLocation::UnknownSize;
@@ -163,7 +165,8 @@
/// Size.
static bool isObjectSmallerThan(const Value *V, uint64_t Size,
const DataLayout &DL,
- const TargetLibraryInfo &TLI) {
+ const TargetLibraryInfo &TLI,
+ bool NullIsValidLoc) {
// Note that the meanings of the "object" are slightly different in the
// following contexts:
// c1: llvm::getObjectSize()
@@ -195,15 +198,16 @@
// This function needs to use the aligned object size because we allow
// reads a bit past the end given sufficient alignment.
- uint64_t ObjectSize = getObjectSize(V, DL, TLI, /*RoundToAlign*/ true);
+ uint64_t ObjectSize = getObjectSize(V, DL, TLI, NullIsValidLoc,
+ /*RoundToAlign*/ true);
return ObjectSize != MemoryLocation::UnknownSize && ObjectSize < Size;
}
/// Returns true if we can prove that the object specified by V has size Size.
static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
- const TargetLibraryInfo &TLI) {
- uint64_t ObjectSize = getObjectSize(V, DL, TLI);
+ const TargetLibraryInfo &TLI, bool NullIsValidLoc) {
+ uint64_t ObjectSize = getObjectSize(V, DL, TLI, NullIsValidLoc);
return ObjectSize != MemoryLocation::UnknownSize && ObjectSize == Size;
}
@@ -1623,10 +1627,10 @@
// Null values in the default address space don't point to any object, so they
// don't alias any other pointer.
if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O1))
- if (CPN->getType()->getAddressSpace() == 0)
+ if (!NullPointerIsDefined(&F, CPN->getType()->getAddressSpace()))
return NoAlias;
if (const ConstantPointerNull *CPN = dyn_cast<ConstantPointerNull>(O2))
- if (CPN->getType()->getAddressSpace() == 0)
+ if (!NullPointerIsDefined(&F, CPN->getType()->getAddressSpace()))
return NoAlias;
if (O1 != O2) {
@@ -1662,10 +1666,11 @@
// If the size of one access is larger than the entire object on the other
// side, then we know such behavior is undefined and can assume no alias.
+ bool NullIsValidLocation = NullPointerIsDefined(&F);
if ((V1Size != MemoryLocation::UnknownSize &&
- isObjectSmallerThan(O2, V1Size, DL, TLI)) ||
+ isObjectSmallerThan(O2, V1Size, DL, TLI, NullIsValidLocation)) ||
(V2Size != MemoryLocation::UnknownSize &&
- isObjectSmallerThan(O1, V2Size, DL, TLI)))
+ isObjectSmallerThan(O1, V2Size, DL, TLI, NullIsValidLocation)))
return NoAlias;
// Check the cache before climbing up use-def chains. This also terminates
@@ -1725,8 +1730,8 @@
if (O1 == O2)
if (V1Size != MemoryLocation::UnknownSize &&
V2Size != MemoryLocation::UnknownSize &&
- (isObjectSize(O1, V1Size, DL, TLI) ||
- isObjectSize(O2, V2Size, DL, TLI)))
+ (isObjectSize(O1, V1Size, DL, TLI, NullIsValidLocation) ||
+ isObjectSize(O2, V2Size, DL, TLI, NullIsValidLocation)))
return AliasCache[Locs] = PartialAlias;
// Recurse back into the best AA results we have, potentially with refined
@@ -1870,6 +1875,7 @@
BasicAAResult BasicAA::run(Function &F, FunctionAnalysisManager &AM) {
return BasicAAResult(F.getParent()->getDataLayout(),
+ F,
AM.getResult<TargetLibraryAnalysis>(F),
AM.getResult<AssumptionAnalysis>(F),
&AM.getResult<DominatorTreeAnalysis>(F),
@@ -1902,7 +1908,7 @@
auto &DTWP = getAnalysis<DominatorTreeWrapperPass>();
auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
- Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), TLIWP.getTLI(),
+ Result.reset(new BasicAAResult(F.getParent()->getDataLayout(), F, TLIWP.getTLI(),
ACT.getAssumptionCache(F), &DTWP.getDomTree(),
LIWP ? &LIWP->getLoopInfo() : nullptr));
@@ -1919,6 +1925,7 @@
BasicAAResult llvm::createLegacyPMBasicAAResult(Pass &P, Function &F) {
return BasicAAResult(
F.getParent()->getDataLayout(),
+ F,
P.getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(),
P.getAnalysis<AssumptionCacheTracker>().getAssumptionCache(F));
}