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[WinEHPrepare] Refactor explicit EH preparation

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Split the preparation machinery into several functions, we will want to
selectively enable/disable different parts of it for an alternative
mechanism for dealing with cross-funclet uses.

llvm-svn: 247834
This commit is contained in:
David Majnemer 2015-09-16 18:40:24 +00:00
parent 78568b0dfc
commit 35bf605dd9
1 changed files with 48 additions and 10 deletions
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58
lib/CodeGen/WinEHPrepare.cpp
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@ -133,6 +133,14 @@ private:
bool prepareExplicitEH(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks);
void colorFunclets(Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks);
void demotePHIsOnFunclets(Function &F);
void demoteUsesBetweenFunclets(Function &F);
void demoteArgumentUses(Function &F);
void cloneCommonBlocks(Function &F,
SmallVectorImpl<BasicBlock *> &EntryBlocks);
void removeImplausibleTerminators(Function &F);
void cleanupPreparedFunclets(Function &F);
void verifyPreparedFunclets(Function &F);
Triple TheTriple;
@ -3288,16 +3296,7 @@ void WinEHPrepare::colorFunclets(Function &F,
}
}
bool WinEHPrepare::prepareExplicitEH(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
// Remove unreachable blocks. It is not valuable to assign them a color and
// their existence can trick us into thinking values are alive when they are
// not.
removeUnreachableBlocks(F);
// Determine which blocks are reachable from which funclet entries.
colorFunclets(F, EntryBlocks);
void WinEHPrepare::demotePHIsOnFunclets(Function &F) {
// Strip PHI nodes off of EH pads.
SmallVector<PHINode *, 16> PHINodes;
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
@ -3324,7 +3323,9 @@ bool WinEHPrepare::prepareExplicitEH(
PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
PN->eraseFromParent();
}
}
void WinEHPrepare::demoteUsesBetweenFunclets(Function &F) {
// Turn all inter-funclet uses of a Value into loads and stores.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
BasicBlock *BB = FI++;
@ -3339,11 +3340,17 @@ bool WinEHPrepare::prepareExplicitEH(
demoteNonlocalUses(I, ColorsForBB, F);
}
}
}
void WinEHPrepare::demoteArgumentUses(Function &F) {
// Also demote function parameters used in funclets.
std::set<BasicBlock *> &ColorsForEntry = BlockColors[&F.getEntryBlock()];
for (Argument &Arg : F.args())
demoteNonlocalUses(&Arg, ColorsForEntry, F);
}
void WinEHPrepare::cloneCommonBlocks(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
// We need to clone all blocks which belong to multiple funclets. Values are
// remapped throughout the funclet to propogate both the new instructions
// *and* the new basic blocks themselves.
@ -3393,7 +3400,9 @@ bool WinEHPrepare::prepareExplicitEH(
for (Instruction &I : *BB)
RemapInstruction(&I, VMap, RF_IgnoreMissingEntries);
}
}
void WinEHPrepare::removeImplausibleTerminators(Function &F) {
// Remove implausible terminators and replace them with UnreachableInst.
for (auto &Funclet : FuncletBlocks) {
BasicBlock *FuncletPadBB = Funclet.first;
@ -3425,7 +3434,9 @@ bool WinEHPrepare::prepareExplicitEH(
}
}
}
}
void WinEHPrepare::cleanupPreparedFunclets(Function &F) {
// Clean-up some of the mess we made by removing useles PHI nodes, trivial
// branches, etc.
for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE;) {
@ -3438,7 +3449,9 @@ bool WinEHPrepare::prepareExplicitEH(
// We might have some unreachable blocks after cleaning up some impossible
// control flow.
removeUnreachableBlocks(F);
}
void WinEHPrepare::verifyPreparedFunclets(Function &F) {
// Recolor the CFG to verify that all is well.
for (BasicBlock &BB : F) {
size_t NumColors = BlockColors[&BB].size();
@ -3452,6 +3465,31 @@ bool WinEHPrepare::prepareExplicitEH(
if (EHPadHasPHI)
report_fatal_error("EH Pad still has a PHI!");
}
}
bool WinEHPrepare::prepareExplicitEH(
Function &F, SmallVectorImpl<BasicBlock *> &EntryBlocks) {
// Remove unreachable blocks. It is not valuable to assign them a color and
// their existence can trick us into thinking values are alive when they are
// not.
removeUnreachableBlocks(F);
// Determine which blocks are reachable from which funclet entries.
colorFunclets(F, EntryBlocks);
demotePHIsOnFunclets(F);
demoteUsesBetweenFunclets(F);
demoteArgumentUses(F);
cloneCommonBlocks(F, EntryBlocks);
removeImplausibleTerminators(F);
cleanupPreparedFunclets(F);
verifyPreparedFunclets(F);
BlockColors.clear();
FuncletBlocks.clear();