6502/llvm-6502
1
0
Fork 0
mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-14 11:32:34 +00:00
Code Issues Projects Releases Wiki Activity

Refactor some code out into its own helper function, getting rid of crazy multiline

Browse Source 
conditionals and commenting the code better.

No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@53526 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2008-07-13 21:12:01 +00:00
parent 56eb133095
commit 1347e87c7b
1 changed files with 84 additions and 54 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

136
lib/Transforms/Utils/SimplifyCFG.cpp
View File

@ -1425,6 +1425,86 @@ static bool SimplifyCondBranchToTwoReturns(BranchInst *BI) {
return true;
}
/// FoldBranchToCommonDest - If this basic block is ONLY a setcc and a branch,
/// and if a predecessor branches to us and one of our successors, fold the
/// setcc into the predecessor and use logical operations to pick the right
/// destination.
static bool FoldBranchToCommonDest(BranchInst *BI) {
Instruction *Cond = dyn_cast<Instruction>(BI->getCondition());
if (Cond == 0) return false;
BasicBlock *BB = BI->getParent();
// Only allow this if the condition is a simple instruction that can be
// executed unconditionally. It must be in the same block as the branch, and
// must be at the front of the block.
if ((!isa<CmpInst>(Cond) && !isa<BinaryOperator>(Cond)) ||
Cond->getParent() != BB || &BB->front() != Cond || !Cond->hasOneUse())
return false;
// Make sure the instruction after the condition is the cond branch.
BasicBlock::iterator CondIt = Cond; ++CondIt;
if (&*CondIt != BI)
return false;
// Finally, don't infinitely unroll conditional loops.
BasicBlock *TrueDest = BI->getSuccessor(0);
BasicBlock *FalseDest = BI->getSuccessor(1);
if (TrueDest == BB || FalseDest == BB)
return false;
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
BasicBlock *PredBlock = *PI;
BranchInst *PBI = dyn_cast<BranchInst>(PredBlock->getTerminator());
if (PBI == 0 || PBI->isUnconditional() ||
!SafeToMergeTerminators(BI, PBI))
continue;
// Canonicalize the predecessors condition (inverting it) if needed to allow
// this xform to trigger.
if (PBI->getSuccessor(0) == FalseDest ||
PBI->getSuccessor(1) == TrueDest) {
Value *NewCond =
BinaryOperator::CreateNot(PBI->getCondition(),
PBI->getCondition()->getName()+".not", PBI);
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
BasicBlock *OldFalse = PBI->getSuccessor(1);
PBI->setSuccessor(0, OldFalse);
PBI->setSuccessor(1, OldTrue);
}
if ((PBI->getSuccessor(0) == TrueDest && FalseDest != BB) ||
(PBI->getSuccessor(1) == FalseDest && TrueDest != BB)) {
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
Instruction *New = Cond->clone();
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
Value *NewCond;
if (PBI->getSuccessor(0) == TrueDest)
NewCond = BinaryOperator::CreateOr(PBI->getCondition(), New, "or.cond",
PBI);
else
NewCond = BinaryOperator::CreateOr(PBI->getCondition(), New, "and.cond",
PBI);
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
PBI->setSuccessor(0, TrueDest);
}
if (PBI->getSuccessor(1) == BB) {
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
return true;
}
}
return false;
}
namespace {
/// ConstantIntOrdering - This class implements a stable ordering of constant
@ -1628,7 +1708,7 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
if (BBI->isTerminator() && // Terminator is the only non-phi instruction!
Succ != BB) // Don't hurt infinite loops!
if (TryToSimplifyUncondBranchFromEmptyBlock(BB, Succ))
return 1;
return true;
} else { // Conditional branch
if (isValueEqualityComparison(BI)) {
@ -1658,59 +1738,9 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
// If this basic block is ONLY a setcc and a branch, and if a predecessor
// branches to us and one of our successors, fold the setcc into the
// predecessor and use logical operations to pick the right destination.
BasicBlock *TrueDest = BI->getSuccessor(0);
BasicBlock *FalseDest = BI->getSuccessor(1);
if (Instruction *Cond = dyn_cast<Instruction>(BI->getCondition())) {
BasicBlock::iterator CondIt = Cond;
if ((isa<CmpInst>(Cond) || isa<BinaryOperator>(Cond)) &&
Cond->getParent() == BB && &BB->front() == Cond &&
&*++CondIt == BI && Cond->hasOneUse() &&
TrueDest != BB && FalseDest != BB)
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI!=E; ++PI)
if (BranchInst *PBI = dyn_cast<BranchInst>((*PI)->getTerminator()))
if (PBI->isConditional() && SafeToMergeTerminators(BI, PBI)) {
BasicBlock *PredBlock = *PI;
if (PBI->getSuccessor(0) == FalseDest ||
PBI->getSuccessor(1) == TrueDest) {
// Invert the predecessors condition test (xor it with true),
// which allows us to write this code once.
Value *NewCond =
BinaryOperator::CreateNot(PBI->getCondition(),
PBI->getCondition()->getName()+".not", PBI);
PBI->setCondition(NewCond);
BasicBlock *OldTrue = PBI->getSuccessor(0);
BasicBlock *OldFalse = PBI->getSuccessor(1);
PBI->setSuccessor(0, OldFalse);
PBI->setSuccessor(1, OldTrue);
}
if ((PBI->getSuccessor(0) == TrueDest && FalseDest != BB) ||
(PBI->getSuccessor(1) == FalseDest && TrueDest != BB)) {
// Clone Cond into the predecessor basic block, and or/and the
// two conditions together.
Instruction *New = Cond->clone();
PredBlock->getInstList().insert(PBI, New);
New->takeName(Cond);
Cond->setName(New->getName()+".old");
Instruction::BinaryOps Opcode =
PBI->getSuccessor(0) == TrueDest ?
Instruction::Or : Instruction::And;
Value *NewCond =
BinaryOperator::Create(Opcode, PBI->getCondition(),
New, "bothcond", PBI);
PBI->setCondition(NewCond);
if (PBI->getSuccessor(0) == BB) {
AddPredecessorToBlock(TrueDest, PredBlock, BB);
PBI->setSuccessor(0, TrueDest);
}
if (PBI->getSuccessor(1) == BB) {
AddPredecessorToBlock(FalseDest, PredBlock, BB);
PBI->setSuccessor(1, FalseDest);
}
if (FoldBranchToCommonDest(BI))
return SimplifyCFG(BB) | 1;
}
}
}
// Scan predessor blocks for conditional branches.
for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)