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Add an option to disable codegen prepare critical edge splitting. In theory, PHI elimination is already doing all (most?) of the splitting needed. But machine-licm and machine-sink seem to miss some important optimizations when splitting is disabled.

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llvm-svn: 111224
This commit is contained in:
Evan Cheng 2010-08-17 01:34:49 +00:00
parent 2bf87a1c77
commit 908b65c371
1 changed files with 14 additions and 6 deletions
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20
lib/Transforms/Scalar/CodeGenPrepare.cpp
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@ -33,6 +33,7 @@
#include "llvm/ADT/SmallSet.h"
#include "llvm/Assembly/Writer.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/PatternMatch.h"
@ -41,6 +42,11 @@
using namespace llvm;
using namespace llvm::PatternMatch;
static cl::opt<bool>
CriticalEdgeSplit("cgp-critical-edge-splitting",
cl::desc("Split critical edges during codegen prepare"),
cl::init(true), cl::Hidden);
namespace {
class CodeGenPrepare : public FunctionPass {
/// TLI - Keep a pointer of a TargetLowering to consult for determining
@ -891,12 +897,14 @@ bool CodeGenPrepare::OptimizeBlock(BasicBlock &BB) {
bool MadeChange = false;
// Split all critical edges where the dest block has a PHI.
TerminatorInst *BBTI = BB.getTerminator();
if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) {
for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
BasicBlock *SuccBB = BBTI->getSuccessor(i);
if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
SplitEdgeNicely(BBTI, i, BackEdges, this);
if (CriticalEdgeSplit) {
TerminatorInst *BBTI = BB.getTerminator();
if (BBTI->getNumSuccessors() > 1 && !isa<IndirectBrInst>(BBTI)) {
for (unsigned i = 0, e = BBTI->getNumSuccessors(); i != e; ++i) {
BasicBlock *SuccBB = BBTI->getSuccessor(i);
if (isa<PHINode>(SuccBB->begin()) && isCriticalEdge(BBTI, i, true))
SplitEdgeNicely(BBTI, i, BackEdges, this);
}
}
}