[PATCH] D11453: [GMR] Fix a long-standing bug in GlobalsModRef where it failed to clear out the per-function modref data structures when functions were deleted or when globals were deleted.
Chandler Carruth
chandlerc at gmail.com
Thu Jul 23 02:02:07 PDT 2015
chandlerc created this revision.
chandlerc added a reviewer: hfinkel.
chandlerc added a subscriber: llvm-commits.
I don't actually know how the global deletion side of this bug hasn't
been hit before, but for the other it just-so-happens that functions
aren't likely to be deleted in the particular part of the LTO pipeline
where we currently enable GMR, so we got lucky.
With this patch, I can self-host with GMR enabled in the normal pass
pipeline!
I was a bit concerned about the compile-time impact of this chang, which
is part of what motivated my prior string of patches to make the
per-function datastructure very dense and fast to walk. With those
changes in place, I can't measure a significant compile time difference
(the difference is around 0.1% which is *way* below the noise) before
and after this patch when building a linked bitcode for all of Clang.
http://reviews.llvm.org/D11453
Files:
lib/Analysis/IPA/GlobalsModRef.cpp
Index: lib/Analysis/IPA/GlobalsModRef.cpp
===================================================================
--- lib/Analysis/IPA/GlobalsModRef.cpp
+++ lib/Analysis/IPA/GlobalsModRef.cpp
@@ -180,6 +180,13 @@
GlobalMRI = ModRefInfo(GlobalMRI | NewMRI);
}
+ /// Clear a global's ModRef info. Should be used when a global is being
+ /// deleted.
+ void eraseModRefInfoForGlobal(const GlobalValue &GV) {
+ if (AlignedMap *P = Info.getPointer())
+ P->Map.erase(&GV);
+ }
+
private:
/// All of the information is encoded into a single pointer, with a three bit
/// integer in the low three bits. The high bit provides a flag for when this
@@ -215,19 +222,26 @@
void deleted() override {
Value *V = getValPtr();
+ if (auto *F = dyn_cast<Function>(V))
+ GMR.FunctionInfos.erase(F);
+
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.
+ // remove any AllocRelatedValues for it.
if (GMR.IndirectGlobals.erase(GV)) {
// Remove any entries in AllocsForIndirectGlobals for this global.
for (auto I = GMR.AllocsForIndirectGlobals.begin(),
E = GMR.AllocsForIndirectGlobals.end();
I != E; ++I)
if (I->second == GV)
GMR.AllocsForIndirectGlobals.erase(I);
}
+
+ // Scan the function info we have collected and remove tihs global
+ // from all of them.
+ for (auto &FIPair : GMR.FunctionInfos)
+ FIPair.second.eraseModRefInfoForGlobal(*GV);
}
}
@@ -361,11 +375,13 @@
/// (really, their address passed to something nontrivial), record this fact,
/// and record the functions that they are used directly in.
void GlobalsModRef::AnalyzeGlobals(Module &M) {
+ SmallPtrSet<Function *, 64> TrackedFunctions;
for (Function &F : M)
if (F.hasLocalLinkage())
if (!AnalyzeUsesOfPointer(&F)) {
// Remember that we are tracking this global.
NonAddressTakenGlobals.insert(&F);
+ TrackedFunctions.insert(&F);
Handles.emplace_front(*this, &F);
Handles.front().I = Handles.begin();
++NumNonAddrTakenFunctions;
@@ -381,12 +397,22 @@
Handles.emplace_front(*this, &GV);
Handles.front().I = Handles.begin();
- for (Function *Reader : Readers)
+ for (Function *Reader : Readers) {
+ if (TrackedFunctions.insert(Reader).second) {
+ Handles.emplace_front(*this, Reader);
+ Handles.front().I = Handles.begin();
+ }
FunctionInfos[Reader].addModRefInfoForGlobal(GV, MRI_Ref);
+ }
if (!GV.isConstant()) // No need to keep track of writers to constants
- for (Function *Writer : Writers)
+ for (Function *Writer : Writers) {
+ if (TrackedFunctions.insert(Writer).second) {
+ Handles.emplace_front(*this, Writer);
+ Handles.front().I = Handles.begin();
+ }
FunctionInfos[Writer].addModRefInfoForGlobal(GV, MRI_Mod);
+ }
++NumNonAddrTakenGlobalVars;
// If this global holds a pointer type, see if it is an indirect global.
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