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[PM/AA] Replace the only use of the AliasAnalysis::deleteValue API (in

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GlobalsModRef) with CallbackVHs that trigger the same behavior.

This is technically more expensive, but in benchmarking some LTO runs,
it seems unlikely to even be above the noise floor. The only way I was
able to measure the performance of GMR at all was to run nothing else
but this one analysis on a linked clang bitcode file. The call graph
analysis still took 5x more time than GMR, and this change at most made
GMR 2% slower (this is well within the noise, so its hard for me to be
sure that this is an actual change). However, in a real LTO run over the
same bitcode, the GMR run takes so little time that the pass timers
don't measure it.

With this, I can remove the last update API from the AliasAnalysis
interface, but I'll actually remove the interface hook point in
a follow-up commit.

Differential Revision: http://reviews.llvm.org/D11324

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@242878 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chandler Carruth 2015-07-22 09:27:58 +00:00
parent 78d824a9ff
commit 0ea4760295
1 changed files with 58 additions and 35 deletions
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93
lib/Analysis/IPA/GlobalsModRef.cpp
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@ -29,6 +29,7 @@
#include "llvm/IR/Module.h"
#include "llvm/Pass.h"
#include "llvm/Support/CommandLine.h"
#include <list>
#include <set>
using namespace llvm;
@ -87,8 +88,7 @@ struct FunctionRecord {
/// GlobalsModRef - The actual analysis pass.
class GlobalsModRef : public ModulePass, public AliasAnalysis {
/// NonAddressTakenGlobals - The globals that do not have their addresses
/// taken.
/// The globals that do not have their addresses taken.
std::set<const GlobalValue *> NonAddressTakenGlobals;
/// IndirectGlobals - The memory pointed to by this global is known to be
@ -103,6 +103,15 @@ class GlobalsModRef : public ModulePass, public AliasAnalysis {
/// modified or read.
std::map<const Function *, FunctionRecord> FunctionInfo;
/// Handle to clear this analysis on deletion of values.
struct DeletionCallbackHandle;
/// List of callbacks for globals being tracked by this analysis. Note that
/// these objects are quite large, but we only anticipate having one per
/// global tracked by this analysis. There are numerous optimizations we
/// could perform to the memory utilization here if this becomes a problem.
std::list<DeletionCallbackHandle> Handles;
public:
static char ID;
GlobalsModRef() : ModulePass(ID) {
@ -171,8 +180,6 @@ public:
return ModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
}
void deleteValue(Value *V) override;
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it
/// should override this to adjust the this pointer as needed for the
@ -214,6 +221,45 @@ INITIALIZE_AG_PASS_END(GlobalsModRef, AliasAnalysis, "globalsmodref-aa",
Pass *llvm::createGlobalsModRefPass() { return new GlobalsModRef(); }
struct final GlobalsModRef::DeletionCallbackHandle : CallbackVH {
GlobalsModRef &GMR;
std::list<DeletionCallbackHandle>::iterator I;
DeletionCallbackHandle(GlobalsModRef &GMR, Value *V)
: CallbackVH(V), GMR(GMR) {}
void deleted() override {
Value *V = getValPtr();
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (GMR.NonAddressTakenGlobals.erase(GV)) {
// This global might be an indirect global. If so, remove it and remove
// any AllocRelatedValues for it.
if (GMR.IndirectGlobals.erase(GV)) {
// Remove any entries in AllocsForIndirectGlobals for this global.
for (std::map<const Value *, const GlobalValue *>::iterator
I = GMR.AllocsForIndirectGlobals.begin(),
E = GMR.AllocsForIndirectGlobals.end();
I != E;) {
if (I->second == GV) {
GMR.AllocsForIndirectGlobals.erase(I++);
} else {
++I;
}
}
}
}
}
// If this is an allocation related to an indirect global, remove it.
GMR.AllocsForIndirectGlobals.erase(V);
// And clear out the handle.
setValPtr(nullptr);
GMR.Handles.erase(I);
// This object is now destroyed!
}
};
/// AnalyzeGlobals - Scan through the users of all of the internal
/// GlobalValue's in the program. If none of them have their "address taken"
/// (really, their address passed to something nontrivial), record this fact,
@ -225,6 +271,8 @@ void GlobalsModRef::AnalyzeGlobals(Module &M) {
if (!AnalyzeUsesOfPointer(&F, Readers, Writers)) {
// Remember that we are tracking this global.
NonAddressTakenGlobals.insert(&F);
Handles.emplace_front(*this, &F);
Handles.front().I = Handles.begin();
++NumNonAddrTakenFunctions;
}
Readers.clear();
@ -236,6 +284,8 @@ void GlobalsModRef::AnalyzeGlobals(Module &M) {
if (!AnalyzeUsesOfPointer(&GV, Readers, Writers)) {
// Remember that we are tracking this global, and the mod/ref fns
NonAddressTakenGlobals.insert(&GV);
Handles.emplace_front(*this, &GV);
Handles.front().I = Handles.begin();
for (Function *Reader : Readers)
FunctionInfo[Reader].GlobalInfo[&GV] |= Ref;
@ -362,9 +412,13 @@ bool GlobalsModRef::AnalyzeIndirectGlobalMemory(GlobalValue *GV) {
// this global in AllocsForIndirectGlobals.
while (!AllocRelatedValues.empty()) {
AllocsForIndirectGlobals[AllocRelatedValues.back()] = GV;
Handles.emplace_front(*this, AllocRelatedValues.back());
Handles.front().I = Handles.begin();
AllocRelatedValues.pop_back();
}
IndirectGlobals.insert(GV);
Handles.emplace_front(*this, GV);
Handles.front().I = Handles.begin();
return true;
}
@ -591,34 +645,3 @@ GlobalsModRef::getModRefInfo(ImmutableCallSite CS, const MemoryLocation &Loc) {
return NoModRef; // No need to query other mod/ref analyses
return ModRefResult(Known & AliasAnalysis::getModRefInfo(CS, Loc));
}
//===----------------------------------------------------------------------===//
// Methods to update the analysis as a result of the client transformation.
//
void GlobalsModRef::deleteValue(Value *V) {
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
if (NonAddressTakenGlobals.erase(GV)) {
// This global might be an indirect global. If so, remove it and remove
// any AllocRelatedValues for it.
if (IndirectGlobals.erase(GV)) {
// Remove any entries in AllocsForIndirectGlobals for this global.
for (std::map<const Value *, const GlobalValue *>::iterator
I = AllocsForIndirectGlobals.begin(),
E = AllocsForIndirectGlobals.end();
I != E;) {
if (I->second == GV) {
AllocsForIndirectGlobals.erase(I++);
} else {
++I;
}
}
}
}
}
// Otherwise, if this is an allocation related to an indirect global, remove
// it.
AllocsForIndirectGlobals.erase(V);
AliasAnalysis::deleteValue(V);
}