RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-12-22 03:28:35 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

It is not safe to execute split condition's true branch first all the time. If split

Browse Source 
condition predicate is GT or GE then execute false branch first.

llvm-svn: 41358
This commit is contained in:
Devang Patel 2007-08-24 06:17:19 +00:00
parent 59af13f0cf
commit 0b351a64db
1 changed files with 35 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
lib/Transforms/Scalar/LoopIndexSplit.cpp
View File

@ -57,7 +57,8 @@ namespace {
class SplitInfo {
public:
SplitInfo() : SplitValue(NULL), SplitCondition(NULL) {}
SplitInfo() : SplitValue(NULL), SplitCondition(NULL),
UseTrueBranchFirst(true) {}
// Induction variable's range is split at this value.
Value *SplitValue;
@ -65,10 +66,14 @@ namespace {
// This compare instruction compares IndVar against SplitValue.
ICmpInst *SplitCondition;
// True if after loop index split, first loop will execute split condition's
// true branch.
bool UseTrueBranchFirst;
// Clear split info.
void clear() {
SplitValue = NULL;
SplitCondition = NULL;
UseTrueBranchFirst = true;
}
};
@ -199,6 +204,9 @@ bool LoopIndexSplit::runOnLoop(Loop *IncomingLoop, LPPassManager &LPM_Ref) {
++SI;
}
if (SplitData.empty())
return false;
// Split most profitiable condition.
// FIXME : Implement cost analysis.
unsigned MostProfitableSDIndex = 0;
@ -341,6 +349,14 @@ void LoopIndexSplit::findSplitCondition() {
if (CI->getPredicate() == ICmpInst::ICMP_NE)
return;
// If split condition predicate is GT or GE then first execute
// false branch of split condition.
if (CI->getPredicate() != ICmpInst::ICMP_ULT
&& CI->getPredicate() != ICmpInst::ICMP_SLT
&& CI->getPredicate() != ICmpInst::ICMP_ULE
&& CI->getPredicate() != ICmpInst::ICMP_SLE)
SD.UseTrueBranchFirst = false;
// If one operand is loop invariant and second operand is SCEVAddRecExpr
// based on induction variable then CI is a candidate split condition.
Value *V0 = CI->getOperand(0);
@ -878,16 +894,30 @@ bool LoopIndexSplit::splitLoop(SplitInfo &SD) {
//[*] Eliminate split condition's inactive branch from ALoop.
BasicBlock *A_SplitCondBlock = SD.SplitCondition->getParent();
BranchInst *A_BR = cast<BranchInst>(A_SplitCondBlock->getTerminator());
BasicBlock *A_InactiveBranch = A_BR->getSuccessor(1);
BasicBlock *A_ActiveBranch = A_BR->getSuccessor(0);
BasicBlock *A_InactiveBranch = NULL;
BasicBlock *A_ActiveBranch = NULL;
if (SD.UseTrueBranchFirst) {
A_ActiveBranch = A_BR->getSuccessor(0);
A_InactiveBranch = A_BR->getSuccessor(1);
} else {
A_ActiveBranch = A_BR->getSuccessor(1);
A_InactiveBranch = A_BR->getSuccessor(0);
}
A_BR->setUnconditionalDest(A_BR->getSuccessor(0));
removeBlocks(A_InactiveBranch, L, A_ActiveBranch);
//[*] Eliminate split condition's inactive branch in from BLoop.
BasicBlock *B_SplitCondBlock = cast<BasicBlock>(ValueMap[A_SplitCondBlock]);
BranchInst *B_BR = cast<BranchInst>(B_SplitCondBlock->getTerminator());
BasicBlock *B_InactiveBranch = B_BR->getSuccessor(0);
BasicBlock *B_ActiveBranch = B_BR->getSuccessor(1);
BasicBlock *B_InactiveBranch = NULL;
BasicBlock *B_ActiveBranch = NULL;
if (SD.UseTrueBranchFirst) {
B_ActiveBranch = B_BR->getSuccessor(1);
B_InactiveBranch = B_BR->getSuccessor(0);
} else {
B_ActiveBranch = B_BR->getSuccessor(0);
B_InactiveBranch = B_BR->getSuccessor(1);
}
B_BR->setUnconditionalDest(B_BR->getSuccessor(1));
removeBlocks(B_InactiveBranch, BLoop, B_ActiveBranch);