RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-24 19:52:54 +01:00
Code Issues Projects Releases Wiki Activity

Implement a simple xform to turn code like this:

Browse Source 
if () { store A -> P; } else { store B -> P; }

into a PHI node with one store, in the most trival case.  This implements
load.ll:test10.

llvm-svn: 23324
This commit is contained in:
Chris Lattner 2005-09-12 23:23:25 +00:00
parent dbe60107c5
commit d35d5d2492
1 changed files with 66 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

66
lib/Transforms/Scalar/InstructionCombining.cpp
View File

@ -5157,6 +5157,72 @@ Instruction *InstCombiner::visitStoreInst(StoreInst &SI) {
if (Instruction *Res = InstCombineStoreToCast(*this, SI)) if (Instruction *Res = InstCombineStoreToCast(*this, SI))
return Res; return Res;
// If this store is the last instruction in the basic block, and if the block
// ends with an unconditional branch, try to move it to the successor block.
BasicBlock::iterator BBI = &SI; ++BBI;
if (BranchInst *BI = dyn_cast<BranchInst>(BBI))
if (BI->isUnconditional()) {
// Check to see if the successor block has exactly two incoming edges. If
// so, see if the other predecessor contains a store to the same location.
// if so, insert a PHI node (if needed) and move the stores down.
BasicBlock *Dest = BI->getSuccessor(0);
pred_iterator PI = pred_begin(Dest);
BasicBlock *Other = 0;
if (*PI != BI->getParent())
Other = *PI;
++PI;
if (PI != pred_end(Dest)) {
if (*PI != BI->getParent())
if (Other)
Other = 0;
else
Other = *PI;
if (++PI != pred_end(Dest))
Other = 0;
}
if (Other) { // If only one other pred...
BBI = Other->getTerminator();
// Make sure this other block ends in an unconditional branch and that
// there is an instruction before the branch.
if (isa<BranchInst>(BBI) && cast<BranchInst>(BBI)->isUnconditional() &&
BBI != Other->begin()) {
--BBI;
StoreInst *OtherStore = dyn_cast<StoreInst>(BBI);
// If this instruction is a store to the same location.
if (OtherStore && OtherStore->getOperand(1) == SI.getOperand(1)) {
// Okay, we know we can perform this transformation. Insert a PHI
// node now if we need it.
Value *MergedVal = OtherStore->getOperand(0);
if (MergedVal != SI.getOperand(0)) {
PHINode *PN = new PHINode(MergedVal->getType(), "storemerge");
PN->reserveOperandSpace(2);
PN->addIncoming(SI.getOperand(0), SI.getParent());
PN->addIncoming(OtherStore->getOperand(0), Other);
MergedVal = InsertNewInstBefore(PN, Dest->front());
}
// Advance to a place where it is safe to insert the new store and
// insert it.
BBI = Dest->begin();
while (isa<PHINode>(BBI)) ++BBI;
InsertNewInstBefore(new StoreInst(MergedVal, SI.getOperand(1),
OtherStore->isVolatile()), *BBI);
// Nuke the old stores.
removeFromWorkList(&SI);
removeFromWorkList(OtherStore);
SI.eraseFromParent();
OtherStore->eraseFromParent();
++NumCombined;
return 0;
}
}
}
}
return 0; return 0;
} }