[llvm-commits] [llvm] r141463 - /llvm/trunk/lib/CodeGen/SjLjEHPrepare.cpp
Bill Wendling
isanbard at gmail.com
Fri Oct 7 17:56:47 PDT 2011
Author: void
Date: Fri Oct 7 19:56:47 2011
New Revision: 141463
URL: http://llvm.org/viewvc/llvm-project?rev=141463&view=rev
Log:
Use the code that lowers the arguments and spills any values which are alive
across unwind edges. This is for the back-end which expects such things.
The code is from the original SjLj EH pass.
Modified:
llvm/trunk/lib/CodeGen/SjLjEHPrepare.cpp
Modified: llvm/trunk/lib/CodeGen/SjLjEHPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SjLjEHPrepare.cpp?rev=141463&r1=141462&r2=141463&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SjLjEHPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/SjLjEHPrepare.cpp Fri Oct 7 19:56:47 2011
@@ -76,6 +76,8 @@
private:
bool setupEntryBlockAndCallSites(Function &F);
Value *setupFunctionContext(Function &F, ArrayRef<LandingPadInst*> LPads);
+ void lowerIncomingArguments(Function &F);
+ void lowerAcrossUnwindEdges(Function &F, ArrayRef<InvokeInst*> Invokes);
void insertCallSiteStore(Instruction *I, int Number, Value *CallSite);
void markInvokeCallSite(InvokeInst *II, int InvokeNo, Value *CallSite,
@@ -345,9 +347,8 @@
bool NeedsSpill = false;
for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
- if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
+ if (UnwindBlock != BB && LiveBBs.count(UnwindBlock))
NeedsSpill = true;
- }
}
// If we decided we need a spill, do it.
@@ -789,6 +790,125 @@
return FuncCtx;
}
+/// lowerIncomingArguments - To avoid having to handle incoming arguments
+/// specially, we lower each arg to a copy instruction in the entry block. This
+/// ensures that the argument value itself cannot be live out of the entry
+/// block.
+void SjLjEHPass::lowerIncomingArguments(Function &F) {
+ BasicBlock::iterator AfterAllocaInsPt = F.begin()->begin();
+ while (isa<AllocaInst>(AfterAllocaInsPt) &&
+ isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsPt)->getArraySize()))
+ ++AfterAllocaInsPt;
+
+ for (Function::arg_iterator
+ AI = F.arg_begin(), AE = F.arg_end(); AI != AE; ++AI) {
+ Type *Ty = AI->getType();
+
+ // Aggregate types can't be cast, but are legal argument types, so we have
+ // to handle them differently. We use an extract/insert pair as a
+ // lightweight method to achieve the same goal.
+ if (isa<StructType>(Ty) || isa<ArrayType>(Ty) || isa<VectorType>(Ty)) {
+ Instruction *EI = ExtractValueInst::Create(AI, 0, "", AfterAllocaInsPt);
+ Instruction *NI = InsertValueInst::Create(AI, EI, 0);
+ NI->insertAfter(EI);
+ AI->replaceAllUsesWith(NI);
+
+ // Set the operand of the instructions back to the AllocaInst.
+ EI->setOperand(0, AI);
+ NI->setOperand(0, AI);
+ } else {
+ // This is always a no-op cast because we're casting AI to AI->getType()
+ // so src and destination types are identical. BitCast is the only
+ // possibility.
+ CastInst *NC =
+ new BitCastInst(AI, AI->getType(), AI->getName() + ".tmp",
+ AfterAllocaInsPt);
+ AI->replaceAllUsesWith(NC);
+
+ // Set the operand of the cast instruction back to the AllocaInst.
+ // Normally it's forbidden to replace a CastInst's operand because it
+ // could cause the opcode to reflect an illegal conversion. However, we're
+ // replacing it here with the same value it was constructed with. We do
+ // this because the above replaceAllUsesWith() clobbered the operand, but
+ // we want this one to remain.
+ NC->setOperand(0, AI);
+ }
+ }
+}
+
+/// lowerAcrossUnwindEdges - Find all variables which are alive across an unwind
+/// edge and spill them.
+void SjLjEHPass::lowerAcrossUnwindEdges(Function &F,
+ ArrayRef<InvokeInst*> Invokes) {
+ // Finally, scan the code looking for instructions with bad live ranges.
+ for (Function::iterator
+ BB = F.begin(), BBE = F.end(); BB != BBE; ++BB) {
+ for (BasicBlock::iterator
+ II = BB->begin(), IIE = BB->end(); II != IIE; ++II) {
+ // Ignore obvious cases we don't have to handle. In particular, most
+ // instructions either have no uses or only have a single use inside the
+ // current block. Ignore them quickly.
+ Instruction *Inst = II;
+ if (Inst->use_empty()) continue;
+ if (Inst->hasOneUse() &&
+ cast<Instruction>(Inst->use_back())->getParent() == BB &&
+ !isa<PHINode>(Inst->use_back())) continue;
+
+ // If this is an alloca in the entry block, it's not a real register
+ // value.
+ if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
+ if (isa<ConstantInt>(AI->getArraySize()) && BB == F.begin())
+ continue;
+
+ // Avoid iterator invalidation by copying users to a temporary vector.
+ SmallVector<Instruction*, 16> Users;
+ for (Value::use_iterator
+ UI = Inst->use_begin(), E = Inst->use_end(); UI != E; ++UI) {
+ Instruction *User = cast<Instruction>(*UI);
+ if (User->getParent() != BB || isa<PHINode>(User))
+ Users.push_back(User);
+ }
+
+ // Find all of the blocks that this value is live in.
+ std::set<BasicBlock*> LiveBBs;
+ LiveBBs.insert(Inst->getParent());
+ while (!Users.empty()) {
+ Instruction *U = Users.back();
+ Users.pop_back();
+
+ if (!isa<PHINode>(U)) {
+ MarkBlocksLiveIn(U->getParent(), LiveBBs);
+ } else {
+ // Uses for a PHI node occur in their predecessor block.
+ PHINode *PN = cast<PHINode>(U);
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
+ if (PN->getIncomingValue(i) == Inst)
+ MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
+ }
+ }
+
+ // Now that we know all of the blocks that this thing is live in, see if
+ // it includes any of the unwind locations.
+ bool NeedsSpill = false;
+ for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
+ BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
+ if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
+ NeedsSpill = true;
+ }
+ }
+
+ // If we decided we need a spill, do it.
+ // FIXME: Spilling this way is overkill, as it forces all uses of
+ // the value to be reloaded from the stack slot, even those that aren't
+ // in the unwind blocks. We should be more selective.
+ if (NeedsSpill) {
+ ++NumSpilled;
+ DemoteRegToStack(*Inst, true);
+ }
+ }
+ }
+}
+
/// setupEntryBlockAndCallSites - Setup the entry block by creating and filling
/// the function context and marking the call sites with the appropriate
/// values. These values are used by the DWARF EH emitter.
@@ -808,6 +928,9 @@
if (Invokes.empty()) return false;
+ lowerIncomingArguments(F);
+ lowerAcrossUnwindEdges(F, Invokes);
+
Value *FuncCtx = setupFunctionContext(F, LPads);
BasicBlock *EntryBB = F.begin();
Type *Int32Ty = Type::getInt32Ty(F.getContext());
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