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-rw-r--r--lib/Transforms/IPO/Inliner.cpp441
1 files changed, 314 insertions, 127 deletions
diff --git a/lib/Transforms/IPO/Inliner.cpp b/lib/Transforms/IPO/Inliner.cpp
index b382837..ea47366 100644
--- a/lib/Transforms/IPO/Inliner.cpp
+++ b/lib/Transforms/IPO/Inliner.cpp
@@ -18,21 +18,25 @@
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Analysis/CallGraph.h"
+#include "llvm/Analysis/InlineCost.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Transforms/IPO/InlinerPass.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/Statistic.h"
#include <set>
using namespace llvm;
STATISTIC(NumInlined, "Number of functions inlined");
STATISTIC(NumDeleted, "Number of functions deleted because all callers found");
+STATISTIC(NumMergedAllocas, "Number of allocas merged together");
static cl::opt<int>
-InlineLimit("inline-threshold", cl::Hidden, cl::init(200),
+InlineLimit("inline-threshold", cl::Hidden, cl::init(200), cl::ZeroOrMore,
cl::desc("Control the amount of inlining to perform (default = 200)"));
Inliner::Inliner(void *ID)
@@ -45,19 +49,32 @@ Inliner::Inliner(void *ID, int Threshold)
/// the call graph. If the derived class implements this method, it should
/// always explicitly call the implementation here.
void Inliner::getAnalysisUsage(AnalysisUsage &Info) const {
- Info.addRequired<TargetData>();
CallGraphSCCPass::getAnalysisUsage(Info);
}
-// InlineCallIfPossible - If it is possible to inline the specified call site,
-// do so and update the CallGraph for this operation.
-bool Inliner::InlineCallIfPossible(CallSite CS, CallGraph &CG,
- const SmallPtrSet<Function*, 8> &SCCFunctions,
- const TargetData &TD) {
+
+typedef DenseMap<const ArrayType*, std::vector<AllocaInst*> >
+InlinedArrayAllocasTy;
+
+/// InlineCallIfPossible - If it is possible to inline the specified call site,
+/// do so and update the CallGraph for this operation.
+///
+/// This function also does some basic book-keeping to update the IR. The
+/// InlinedArrayAllocas map keeps track of any allocas that are already
+/// available from other functions inlined into the caller. If we are able to
+/// inline this call site we attempt to reuse already available allocas or add
+/// any new allocas to the set if not possible.
+static bool InlineCallIfPossible(CallSite CS, CallGraph &CG,
+ const TargetData *TD,
+ InlinedArrayAllocasTy &InlinedArrayAllocas) {
Function *Callee = CS.getCalledFunction();
Function *Caller = CS.getCaller();
- if (!InlineFunction(CS, &CG, &TD)) return false;
+ // Try to inline the function. Get the list of static allocas that were
+ // inlined.
+ SmallVector<AllocaInst*, 16> StaticAllocas;
+ if (!InlineFunction(CS, &CG, TD, &StaticAllocas))
+ return false;
// If the inlined function had a higher stack protection level than the
// calling function, then bump up the caller's stack protection level.
@@ -67,23 +84,89 @@ bool Inliner::InlineCallIfPossible(CallSite CS, CallGraph &CG,
!Caller->hasFnAttr(Attribute::StackProtectReq))
Caller->addFnAttr(Attribute::StackProtect);
- // If we inlined the last possible call site to the function, delete the
- // function body now.
- if (Callee->use_empty() && (Callee->hasLocalLinkage() ||
- Callee->hasAvailableExternallyLinkage()) &&
- !SCCFunctions.count(Callee)) {
- DOUT << " -> Deleting dead function: " << Callee->getName() << "\n";
- CallGraphNode *CalleeNode = CG[Callee];
-
- // Remove any call graph edges from the callee to its callees.
- CalleeNode->removeAllCalledFunctions();
-
- resetCachedCostInfo(CalleeNode->getFunction());
+
+ // Look at all of the allocas that we inlined through this call site. If we
+ // have already inlined other allocas through other calls into this function,
+ // then we know that they have disjoint lifetimes and that we can merge them.
+ //
+ // There are many heuristics possible for merging these allocas, and the
+ // different options have different tradeoffs. One thing that we *really*
+ // don't want to hurt is SRoA: once inlining happens, often allocas are no
+ // longer address taken and so they can be promoted.
+ //
+ // Our "solution" for that is to only merge allocas whose outermost type is an
+ // array type. These are usually not promoted because someone is using a
+ // variable index into them. These are also often the most important ones to
+ // merge.
+ //
+ // A better solution would be to have real memory lifetime markers in the IR
+ // and not have the inliner do any merging of allocas at all. This would
+ // allow the backend to do proper stack slot coloring of all allocas that
+ // *actually make it to the backend*, which is really what we want.
+ //
+ // Because we don't have this information, we do this simple and useful hack.
+ //
+ SmallPtrSet<AllocaInst*, 16> UsedAllocas;
+
+ // Loop over all the allocas we have so far and see if they can be merged with
+ // a previously inlined alloca. If not, remember that we had it.
+ for (unsigned AllocaNo = 0, e = StaticAllocas.size();
+ AllocaNo != e; ++AllocaNo) {
+ AllocaInst *AI = StaticAllocas[AllocaNo];
+
+ // Don't bother trying to merge array allocations (they will usually be
+ // canonicalized to be an allocation *of* an array), or allocations whose
+ // type is not itself an array (because we're afraid of pessimizing SRoA).
+ const ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
+ if (ATy == 0 || AI->isArrayAllocation())
+ continue;
+
+ // Get the list of all available allocas for this array type.
+ std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
+
+ // Loop over the allocas in AllocasForType to see if we can reuse one. Note
+ // that we have to be careful not to reuse the same "available" alloca for
+ // multiple different allocas that we just inlined, we use the 'UsedAllocas'
+ // set to keep track of which "available" allocas are being used by this
+ // function. Also, AllocasForType can be empty of course!
+ bool MergedAwayAlloca = false;
+ for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
+ AllocaInst *AvailableAlloca = AllocasForType[i];
+
+ // The available alloca has to be in the right function, not in some other
+ // function in this SCC.
+ if (AvailableAlloca->getParent() != AI->getParent())
+ continue;
+
+ // If the inlined function already uses this alloca then we can't reuse
+ // it.
+ if (!UsedAllocas.insert(AvailableAlloca))
+ continue;
+
+ // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
+ // success!
+ DEBUG(errs() << " ***MERGED ALLOCA: " << *AI);
+
+ AI->replaceAllUsesWith(AvailableAlloca);
+ AI->eraseFromParent();
+ MergedAwayAlloca = true;
+ ++NumMergedAllocas;
+ break;
+ }
- // Removing the node for callee from the call graph and delete it.
- delete CG.removeFunctionFromModule(CalleeNode);
- ++NumDeleted;
+ // If we already nuked the alloca, we're done with it.
+ if (MergedAwayAlloca)
+ continue;
+
+ // If we were unable to merge away the alloca either because there are no
+ // allocas of the right type available or because we reused them all
+ // already, remember that this alloca came from an inlined function and mark
+ // it used so we don't reuse it for other allocas from this inline
+ // operation.
+ AllocasForType.push_back(AI);
+ UsedAllocas.insert(AI);
}
+
return true;
}
@@ -91,69 +174,145 @@ bool Inliner::InlineCallIfPossible(CallSite CS, CallGraph &CG,
/// at the given CallSite.
bool Inliner::shouldInline(CallSite CS) {
InlineCost IC = getInlineCost(CS);
- float FudgeFactor = getInlineFudgeFactor(CS);
if (IC.isAlways()) {
- DOUT << " Inlining: cost=always"
- << ", Call: " << *CS.getInstruction();
+ DEBUG(errs() << " Inlining: cost=always"
+ << ", Call: " << *CS.getInstruction() << "\n");
return true;
}
if (IC.isNever()) {
- DOUT << " NOT Inlining: cost=never"
- << ", Call: " << *CS.getInstruction();
+ DEBUG(errs() << " NOT Inlining: cost=never"
+ << ", Call: " << *CS.getInstruction() << "\n");
return false;
}
int Cost = IC.getValue();
int CurrentThreshold = InlineThreshold;
- Function *Fn = CS.getCaller();
- if (Fn && !Fn->isDeclaration()
- && Fn->hasFnAttr(Attribute::OptimizeForSize)
- && InlineThreshold != 50) {
+ Function *Caller = CS.getCaller();
+ if (Caller && !Caller->isDeclaration() &&
+ Caller->hasFnAttr(Attribute::OptimizeForSize) &&
+ InlineLimit.getNumOccurrences() == 0 &&
+ InlineThreshold != 50)
CurrentThreshold = 50;
- }
+ float FudgeFactor = getInlineFudgeFactor(CS);
if (Cost >= (int)(CurrentThreshold * FudgeFactor)) {
- DOUT << " NOT Inlining: cost=" << Cost
- << ", Call: " << *CS.getInstruction();
+ DEBUG(errs() << " NOT Inlining: cost=" << Cost
+ << ", Call: " << *CS.getInstruction() << "\n");
return false;
- } else {
- DOUT << " Inlining: cost=" << Cost
- << ", Call: " << *CS.getInstruction();
- return true;
}
+
+ // Try to detect the case where the current inlining candidate caller
+ // (call it B) is a static function and is an inlining candidate elsewhere,
+ // and the current candidate callee (call it C) is large enough that
+ // inlining it into B would make B too big to inline later. In these
+ // circumstances it may be best not to inline C into B, but to inline B
+ // into its callers.
+ if (Caller->hasLocalLinkage()) {
+ int TotalSecondaryCost = 0;
+ bool outerCallsFound = false;
+ bool allOuterCallsWillBeInlined = true;
+ bool someOuterCallWouldNotBeInlined = false;
+ for (Value::use_iterator I = Caller->use_begin(), E =Caller->use_end();
+ I != E; ++I) {
+ CallSite CS2 = CallSite::get(*I);
+
+ // If this isn't a call to Caller (it could be some other sort
+ // of reference) skip it.
+ if (CS2.getInstruction() == 0 || CS2.getCalledFunction() != Caller)
+ continue;
+
+ InlineCost IC2 = getInlineCost(CS2);
+ if (IC2.isNever())
+ allOuterCallsWillBeInlined = false;
+ if (IC2.isAlways() || IC2.isNever())
+ continue;
+
+ outerCallsFound = true;
+ int Cost2 = IC2.getValue();
+ int CurrentThreshold2 = InlineThreshold;
+ Function *Caller2 = CS2.getCaller();
+ if (Caller2 && !Caller2->isDeclaration() &&
+ Caller2->hasFnAttr(Attribute::OptimizeForSize) &&
+ InlineThreshold != 50)
+ CurrentThreshold2 = 50;
+
+ float FudgeFactor2 = getInlineFudgeFactor(CS2);
+
+ if (Cost2 >= (int)(CurrentThreshold2 * FudgeFactor2))
+ allOuterCallsWillBeInlined = false;
+
+ // See if we have this case. We subtract off the penalty
+ // for the call instruction, which we would be deleting.
+ if (Cost2 < (int)(CurrentThreshold2 * FudgeFactor2) &&
+ Cost2 + Cost - (InlineConstants::CallPenalty + 1) >=
+ (int)(CurrentThreshold2 * FudgeFactor2)) {
+ someOuterCallWouldNotBeInlined = true;
+ TotalSecondaryCost += Cost2;
+ }
+ }
+ // If all outer calls to Caller would get inlined, the cost for the last
+ // one is set very low by getInlineCost, in anticipation that Caller will
+ // be removed entirely. We did not account for this above unless there
+ // is only one caller of Caller.
+ if (allOuterCallsWillBeInlined && Caller->use_begin() != Caller->use_end())
+ TotalSecondaryCost += InlineConstants::LastCallToStaticBonus;
+
+ if (outerCallsFound && someOuterCallWouldNotBeInlined &&
+ TotalSecondaryCost < Cost) {
+ DEBUG(errs() << " NOT Inlining: " << *CS.getInstruction() <<
+ " Cost = " << Cost <<
+ ", outer Cost = " << TotalSecondaryCost << '\n');
+ return false;
+ }
+ }
+
+ DEBUG(errs() << " Inlining: cost=" << Cost
+ << ", Call: " << *CS.getInstruction() << '\n');
+ return true;
}
-bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
+bool Inliner::runOnSCC(std::vector<CallGraphNode*> &SCC) {
CallGraph &CG = getAnalysis<CallGraph>();
- TargetData &TD = getAnalysis<TargetData>();
+ const TargetData *TD = getAnalysisIfAvailable<TargetData>();
SmallPtrSet<Function*, 8> SCCFunctions;
- DOUT << "Inliner visiting SCC:";
+ DEBUG(errs() << "Inliner visiting SCC:");
for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
Function *F = SCC[i]->getFunction();
if (F) SCCFunctions.insert(F);
- DOUT << " " << (F ? F->getName() : "INDIRECTNODE");
+ DEBUG(errs() << " " << (F ? F->getName() : "INDIRECTNODE"));
}
// Scan through and identify all call sites ahead of time so that we only
// inline call sites in the original functions, not call sites that result
// from inlining other functions.
- std::vector<CallSite> CallSites;
+ SmallVector<CallSite, 16> CallSites;
- for (unsigned i = 0, e = SCC.size(); i != e; ++i)
- if (Function *F = SCC[i]->getFunction())
- for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
- for (BasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
- CallSite CS = CallSite::get(I);
- if (CS.getInstruction() && !isa<DbgInfoIntrinsic>(I) &&
- (!CS.getCalledFunction() ||
- !CS.getCalledFunction()->isDeclaration()))
- CallSites.push_back(CS);
- }
+ for (unsigned i = 0, e = SCC.size(); i != e; ++i) {
+ Function *F = SCC[i]->getFunction();
+ if (!F) continue;
+
+ for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ CallSite CS = CallSite::get(I);
+ // If this isn't a call, or it is a call to an intrinsic, it can
+ // never be inlined.
+ if (CS.getInstruction() == 0 || isa<IntrinsicInst>(I))
+ continue;
+
+ // If this is a direct call to an external function, we can never inline
+ // it. If it is an indirect call, inlining may resolve it to be a
+ // direct call, so we keep it.
+ if (CS.getCalledFunction() && CS.getCalledFunction()->isDeclaration())
+ continue;
+
+ CallSites.push_back(CS);
+ }
+ }
- DOUT << ": " << CallSites.size() << " call sites.\n";
+ DEBUG(errs() << ": " << CallSites.size() << " call sites.\n");
// Now that we have all of the call sites, move the ones to functions in the
// current SCC to the end of the list.
@@ -163,6 +322,9 @@ bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
if (SCCFunctions.count(F))
std::swap(CallSites[i--], CallSites[--FirstCallInSCC]);
+
+ InlinedArrayAllocasTy InlinedArrayAllocas;
+
// Now that we have all of the call sites, loop over them and inline them if
// it looks profitable to do so.
bool Changed = false;
@@ -171,51 +333,68 @@ bool Inliner::runOnSCC(const std::vector<CallGraphNode*> &SCC) {
LocalChange = false;
// Iterate over the outer loop because inlining functions can cause indirect
// calls to become direct calls.
- for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi)
- if (Function *Callee = CallSites[CSi].getCalledFunction()) {
- // Calls to external functions are never inlinable.
- if (Callee->isDeclaration()) {
- if (SCC.size() == 1) {
- std::swap(CallSites[CSi], CallSites.back());
- CallSites.pop_back();
- } else {
- // Keep the 'in SCC / not in SCC' boundary correct.
- CallSites.erase(CallSites.begin()+CSi);
- }
- --CSi;
- continue;
- }
-
- // If the policy determines that we should inline this function,
- // try to do so.
- CallSite CS = CallSites[CSi];
- if (shouldInline(CS)) {
- Function *Caller = CS.getCaller();
- // Attempt to inline the function...
- if (InlineCallIfPossible(CS, CG, SCCFunctions, TD)) {
- // Remove any cached cost info for this caller, as inlining the
- // callee has increased the size of the caller (which may be the
- // same as the callee).
- resetCachedCostInfo(Caller);
-
- // Remove this call site from the list. If possible, use
- // swap/pop_back for efficiency, but do not use it if doing so would
- // move a call site to a function in this SCC before the
- // 'FirstCallInSCC' barrier.
- if (SCC.size() == 1) {
- std::swap(CallSites[CSi], CallSites.back());
- CallSites.pop_back();
- } else {
- CallSites.erase(CallSites.begin()+CSi);
- }
- --CSi;
-
- ++NumInlined;
- Changed = true;
- LocalChange = true;
- }
- }
+ for (unsigned CSi = 0; CSi != CallSites.size(); ++CSi) {
+ CallSite CS = CallSites[CSi];
+
+ Function *Callee = CS.getCalledFunction();
+ // We can only inline direct calls to non-declarations.
+ if (Callee == 0 || Callee->isDeclaration()) continue;
+
+ // If the policy determines that we should inline this function,
+ // try to do so.
+ if (!shouldInline(CS))
+ continue;
+
+ Function *Caller = CS.getCaller();
+ // Attempt to inline the function...
+ if (!InlineCallIfPossible(CS, CG, TD, InlinedArrayAllocas))
+ continue;
+
+ // If we inlined the last possible call site to the function, delete the
+ // function body now.
+ if (Callee->use_empty() && Callee->hasLocalLinkage() &&
+ // TODO: Can remove if in SCC now.
+ !SCCFunctions.count(Callee) &&
+
+ // The function may be apparently dead, but if there are indirect
+ // callgraph references to the node, we cannot delete it yet, this
+ // could invalidate the CGSCC iterator.
+ CG[Callee]->getNumReferences() == 0) {
+ DEBUG(errs() << " -> Deleting dead function: "
+ << Callee->getName() << "\n");
+ CallGraphNode *CalleeNode = CG[Callee];
+
+ // Remove any call graph edges from the callee to its callees.
+ CalleeNode->removeAllCalledFunctions();
+
+ resetCachedCostInfo(Callee);
+
+ // Removing the node for callee from the call graph and delete it.
+ delete CG.removeFunctionFromModule(CalleeNode);
+ ++NumDeleted;
}
+
+ // Remove any cached cost info for this caller, as inlining the
+ // callee has increased the size of the caller (which may be the
+ // same as the callee).
+ resetCachedCostInfo(Caller);
+
+ // Remove this call site from the list. If possible, use
+ // swap/pop_back for efficiency, but do not use it if doing so would
+ // move a call site to a function in this SCC before the
+ // 'FirstCallInSCC' barrier.
+ if (SCC.size() == 1) {
+ std::swap(CallSites[CSi], CallSites.back());
+ CallSites.pop_back();
+ } else {
+ CallSites.erase(CallSites.begin()+CSi);
+ }
+ --CSi;
+
+ ++NumInlined;
+ Changed = true;
+ LocalChange = true;
+ }
} while (LocalChange);
return Changed;
@@ -227,47 +406,55 @@ bool Inliner::doFinalization(CallGraph &CG) {
return removeDeadFunctions(CG);
}
- /// removeDeadFunctions - Remove dead functions that are not included in
- /// DNR (Do Not Remove) list.
+/// removeDeadFunctions - Remove dead functions that are not included in
+/// DNR (Do Not Remove) list.
bool Inliner::removeDeadFunctions(CallGraph &CG,
- SmallPtrSet<const Function *, 16> *DNR) {
- std::set<CallGraphNode*> FunctionsToRemove;
+ SmallPtrSet<const Function *, 16> *DNR) {
+ SmallPtrSet<CallGraphNode*, 16> FunctionsToRemove;
// Scan for all of the functions, looking for ones that should now be removed
// from the program. Insert the dead ones in the FunctionsToRemove set.
for (CallGraph::iterator I = CG.begin(), E = CG.end(); I != E; ++I) {
CallGraphNode *CGN = I->second;
- if (Function *F = CGN ? CGN->getFunction() : 0) {
- // If the only remaining users of the function are dead constants, remove
- // them.
- F->removeDeadConstantUsers();
-
- if (DNR && DNR->count(F))
- continue;
+ if (CGN->getFunction() == 0)
+ continue;
+
+ Function *F = CGN->getFunction();
+
+ // If the only remaining users of the function are dead constants, remove
+ // them.
+ F->removeDeadConstantUsers();
+
+ if (DNR && DNR->count(F))
+ continue;
+ if (!F->hasLinkOnceLinkage() && !F->hasLocalLinkage() &&
+ !F->hasAvailableExternallyLinkage())
+ continue;
+ if (!F->use_empty())
+ continue;
+
+ // Remove any call graph edges from the function to its callees.
+ CGN->removeAllCalledFunctions();
+
+ // Remove any edges from the external node to the function's call graph
+ // node. These edges might have been made irrelegant due to
+ // optimization of the program.
+ CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
- if ((F->hasLinkOnceLinkage() || F->hasLocalLinkage()) &&
- F->use_empty()) {
-
- // Remove any call graph edges from the function to its callees.
- CGN->removeAllCalledFunctions();
-
- // Remove any edges from the external node to the function's call graph
- // node. These edges might have been made irrelegant due to
- // optimization of the program.
- CG.getExternalCallingNode()->removeAnyCallEdgeTo(CGN);
-
- // Removing the node for callee from the call graph and delete it.
- FunctionsToRemove.insert(CGN);
- }
- }
+ // Removing the node for callee from the call graph and delete it.
+ FunctionsToRemove.insert(CGN);
}
// Now that we know which functions to delete, do so. We didn't want to do
// this inline, because that would invalidate our CallGraph::iterator
// objects. :(
+ //
+ // Note that it doesn't matter that we are iterating over a non-stable set
+ // here to do this, it doesn't matter which order the functions are deleted
+ // in.
bool Changed = false;
- for (std::set<CallGraphNode*>::iterator I = FunctionsToRemove.begin(),
- E = FunctionsToRemove.end(); I != E; ++I) {
+ for (SmallPtrSet<CallGraphNode*, 16>::iterator I = FunctionsToRemove.begin(),
+ E = FunctionsToRemove.end(); I != E; ++I) {
resetCachedCostInfo((*I)->getFunction());
delete CG.removeFunctionFromModule(*I);
++NumDeleted;
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