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Add a new beta option for critical edge splitting, to avoid a problem that

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Nate noticed in yacr2 (and I know occurs in other places as well).

This is still rough, as the critical edge blocks are not intelligently placed
but is added to get some idea to see if this improves performance.

llvm-svn: 22825
This commit is contained in:
Chris Lattner 2005-08-17 06:37:43 +00:00
parent 969232d2ec
commit dbfcba7565
1 changed files with 23 additions and 0 deletions
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23
lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp
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@ -29,12 +29,18 @@
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <map>
#include <iostream>
using namespace llvm;
static cl::opt<bool>
SplitPHICritEdges("split-phi-constant-crit-edges", cl::Hidden,
cl::desc("Split critical edges for PHI values that are constants"));
#ifndef _NDEBUG
static cl::opt<bool>
ViewDAGs("view-isel-dags", cl::Hidden,
@ -959,6 +965,10 @@ unsigned SelectionDAGISel::MakeReg(MVT::ValueType VT) {
return RegMap->createVirtualRegister(TLI.getRegClassFor(VT));
}
void SelectionDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
if (!SplitPHICritEdges)
AU.setPreservesAll();
}
bool SelectionDAGISel::runOnFunction(Function &Fn) {
@ -966,6 +976,19 @@ bool SelectionDAGISel::runOnFunction(Function &Fn) {
RegMap = MF.getSSARegMap();
DEBUG(std::cerr << "\n\n\n=== " << Fn.getName() << "\n");
// First pass, split all critical edges for PHI nodes with incoming values
// that are constants, this way the load of the constant into a vreg will not
// be placed into MBBs that are used some other way.
if (SplitPHICritEdges)
for (Function::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
PHINode *PN;
for (BasicBlock::iterator BBI = BB->begin();
(PN = dyn_cast<PHINode>(BBI)); ++BBI)
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
if (isa<Constant>(PN->getIncomingValue(i)))
SplitCriticalEdge(PN->getIncomingBlock(i), BB);
}
FunctionLoweringInfo FuncInfo(TLI, Fn, MF);
for (Function::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I)