6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2025-06-19 18:24:00 +00:00
Code Issues Projects Releases Wiki Activity

CVP: If we have a PHI with an incoming select, try to skip the select.

Browse Source 
This is a common pattern with dyn_cast and similar constructs, when the
PHI no longer depends on the select it can often be turned into a simpler
construct or even get hoisted out of the loop.

PR15340.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@175995 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Benjamin Kramer
2013-02-24 15:34:43 +00:00
parent bd4b21ea41
commit e8aa36a4af
2 changed files with 44 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
lib/Transforms/Scalar/CorrelatedValuePropagation.cpp
View File

@ -21,6 +21,8 @@
#include "llvm/IR/Instructions.h"
#include "llvm/Pass.h"
#include "llvm/Support/CFG.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Transforms/Utils/Local.h"
using namespace llvm;
@ -97,12 +99,29 @@ bool CorrelatedValuePropagation::processPHI(PHINode *P) {
Value *Incoming = P->getIncomingValue(i);
if (isa<Constant>(Incoming)) continue;
Constant *C = LVI->getConstantOnEdge(P->getIncomingValue(i),
P->getIncomingBlock(i),
BB);
if (!C) continue;
Value *V = LVI->getConstantOnEdge(Incoming, P->getIncomingBlock(i), BB);
P->setIncomingValue(i, C);
// Look if the incoming value is a select with a constant but LVI tells us
// that the incoming value can never be that constant. In that case replace
// the incoming value with the other value of the select. This often allows
// us to remove the select later.
if (!V) {
SelectInst *SI = dyn_cast<SelectInst>(Incoming);
if (!SI) continue;
Constant *C = dyn_cast<Constant>(SI->getFalseValue());
if (!C) continue;
if (LVI->getPredicateOnEdge(ICmpInst::ICMP_EQ, SI, C,
P->getIncomingBlock(i), BB) !=
LazyValueInfo::False)
continue;
DEBUG(dbgs() << "CVP: Threading PHI over " << *SI << '\n');
V = SI->getTrueValue();
}
P->setIncomingValue(i, V);
Changed = true;
}