138 lines
5.2 KiB
C++
138 lines
5.2 KiB
C++
//===- LibCallAliasAnalysis.cpp - Implement AliasAnalysis for libcalls ----===//
|
|
//
|
|
// The LLVM Compiler Infrastructure
|
|
//
|
|
// This file is distributed under the University of Illinois Open Source
|
|
// License. See LICENSE.TXT for details.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
//
|
|
// This file implements the LibCallAliasAnalysis class.
|
|
//
|
|
//===----------------------------------------------------------------------===//
|
|
|
|
#include "llvm/Analysis/LibCallAliasAnalysis.h"
|
|
#include "llvm/Analysis/Passes.h"
|
|
#include "llvm/Analysis/LibCallSemantics.h"
|
|
#include "llvm/Function.h"
|
|
#include "llvm/Pass.h"
|
|
using namespace llvm;
|
|
|
|
// Register this pass...
|
|
char LibCallAliasAnalysis::ID = 0;
|
|
INITIALIZE_AG_PASS(LibCallAliasAnalysis, AliasAnalysis, "libcall-aa",
|
|
"LibCall Alias Analysis", false, true, false);
|
|
|
|
FunctionPass *llvm::createLibCallAliasAnalysisPass(LibCallInfo *LCI) {
|
|
return new LibCallAliasAnalysis(LCI);
|
|
}
|
|
|
|
LibCallAliasAnalysis::~LibCallAliasAnalysis() {
|
|
delete LCI;
|
|
}
|
|
|
|
void LibCallAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
|
|
AliasAnalysis::getAnalysisUsage(AU);
|
|
AU.setPreservesAll(); // Does not transform code
|
|
}
|
|
|
|
|
|
|
|
/// AnalyzeLibCallDetails - Given a call to a function with the specified
|
|
/// LibCallFunctionInfo, see if we can improve the mod/ref footprint of the call
|
|
/// vs the specified pointer/size.
|
|
AliasAnalysis::ModRefResult
|
|
LibCallAliasAnalysis::AnalyzeLibCallDetails(const LibCallFunctionInfo *FI,
|
|
ImmutableCallSite CS, const Value *P,
|
|
unsigned Size) {
|
|
// If we have a function, check to see what kind of mod/ref effects it
|
|
// has. Start by including any info globally known about the function.
|
|
AliasAnalysis::ModRefResult MRInfo = FI->UniversalBehavior;
|
|
if (MRInfo == NoModRef) return MRInfo;
|
|
|
|
// If that didn't tell us that the function is 'readnone', check to see
|
|
// if we have detailed info and if 'P' is any of the locations we know
|
|
// about.
|
|
const LibCallFunctionInfo::LocationMRInfo *Details = FI->LocationDetails;
|
|
if (Details == 0)
|
|
return MRInfo;
|
|
|
|
// If the details array is of the 'DoesNot' kind, we only know something if
|
|
// the pointer is a match for one of the locations in 'Details'. If we find a
|
|
// match, we can prove some interactions cannot happen.
|
|
//
|
|
if (FI->DetailsType == LibCallFunctionInfo::DoesNot) {
|
|
// Find out if the pointer refers to a known location.
|
|
for (unsigned i = 0; Details[i].LocationID != ~0U; ++i) {
|
|
const LibCallLocationInfo &Loc =
|
|
LCI->getLocationInfo(Details[i].LocationID);
|
|
LibCallLocationInfo::LocResult Res = Loc.isLocation(CS, P, Size);
|
|
if (Res != LibCallLocationInfo::Yes) continue;
|
|
|
|
// If we find a match against a location that we 'do not' interact with,
|
|
// learn this info into MRInfo.
|
|
return ModRefResult(MRInfo & ~Details[i].MRInfo);
|
|
}
|
|
return MRInfo;
|
|
}
|
|
|
|
// If the details are of the 'DoesOnly' sort, we know something if the pointer
|
|
// is a match for one of the locations in 'Details'. Also, if we can prove
|
|
// that the pointers is *not* one of the locations in 'Details', we know that
|
|
// the call is NoModRef.
|
|
assert(FI->DetailsType == LibCallFunctionInfo::DoesOnly);
|
|
|
|
// Find out if the pointer refers to a known location.
|
|
bool NoneMatch = true;
|
|
for (unsigned i = 0; Details[i].LocationID != ~0U; ++i) {
|
|
const LibCallLocationInfo &Loc =
|
|
LCI->getLocationInfo(Details[i].LocationID);
|
|
LibCallLocationInfo::LocResult Res = Loc.isLocation(CS, P, Size);
|
|
if (Res == LibCallLocationInfo::No) continue;
|
|
|
|
// If we don't know if this pointer points to the location, then we have to
|
|
// assume it might alias in some case.
|
|
if (Res == LibCallLocationInfo::Unknown) {
|
|
NoneMatch = false;
|
|
continue;
|
|
}
|
|
|
|
// If we know that this pointer definitely is pointing into the location,
|
|
// merge in this information.
|
|
return ModRefResult(MRInfo & Details[i].MRInfo);
|
|
}
|
|
|
|
// If we found that the pointer is guaranteed to not match any of the
|
|
// locations in our 'DoesOnly' rule, then we know that the pointer must point
|
|
// to some other location. Since the libcall doesn't mod/ref any other
|
|
// locations, return NoModRef.
|
|
if (NoneMatch)
|
|
return NoModRef;
|
|
|
|
// Otherwise, return any other info gained so far.
|
|
return MRInfo;
|
|
}
|
|
|
|
// getModRefInfo - Check to see if the specified callsite can clobber the
|
|
// specified memory object.
|
|
//
|
|
AliasAnalysis::ModRefResult
|
|
LibCallAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
|
|
const Value *P, unsigned Size) {
|
|
ModRefResult MRInfo = ModRef;
|
|
|
|
// If this is a direct call to a function that LCI knows about, get the
|
|
// information about the runtime function.
|
|
if (LCI) {
|
|
if (const Function *F = CS.getCalledFunction()) {
|
|
if (const LibCallFunctionInfo *FI = LCI->getFunctionInfo(F)) {
|
|
MRInfo = ModRefResult(MRInfo & AnalyzeLibCallDetails(FI, CS, P, Size));
|
|
if (MRInfo == NoModRef) return NoModRef;
|
|
}
|
|
}
|
|
}
|
|
|
|
// The AliasAnalysis base class has some smarts, lets use them.
|
|
return (ModRefResult)(MRInfo | AliasAnalysis::getModRefInfo(CS, P, Size));
|
|
}
|