mirror of
https://github.com/RPCS3/llvm.git
synced 2024-12-07 19:47:09 +00:00
Allow more cmp / bcc to be predicated; clean up triangle ifcvt checking code.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37518 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
parent
1fc7cb695c
commit
ac5f142b9f
@ -98,13 +98,14 @@ namespace {
|
||||
|
||||
private:
|
||||
bool ReverseBranchCondition(BBInfo &BBI);
|
||||
bool BlockModifyPredicate(MachineBasicBlock *BB) const;
|
||||
bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI) const;
|
||||
bool ValidSimple(BBInfo &TrueBBI) const;
|
||||
bool ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
|
||||
bool FalseBranch = false) const;
|
||||
bool ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI) const;
|
||||
void StructuralAnalysis(MachineBasicBlock *BB);
|
||||
bool FeasibilityAnalysis(BBInfo &BBI,
|
||||
std::vector<MachineOperand> &Cond,
|
||||
bool IgnoreTerm = false);
|
||||
void ScanInstructions(BBInfo &BBI);
|
||||
void AnalyzeBlock(MachineBasicBlock *BB);
|
||||
bool FeasibilityAnalysis(BBInfo &BBI, std::vector<MachineOperand> &Cond,
|
||||
bool isTriangle = false, bool RevBranch = false);
|
||||
bool AttemptRestructuring(BBInfo &BBI);
|
||||
bool AnalyzeBlocks(MachineFunction &MF,
|
||||
std::vector<BBInfo*> &Candidates);
|
||||
@ -235,47 +236,44 @@ bool IfConverter::ReverseBranchCondition(BBInfo &BBI) {
|
||||
return false;
|
||||
}
|
||||
|
||||
/// BlockModifyPredicate - Returns true if any instruction in the block may
|
||||
/// clobber the condition code or register(s) used to predicate instructions,
|
||||
/// e.g. call, cmp.
|
||||
bool IfConverter::BlockModifyPredicate(MachineBasicBlock *BB) const {
|
||||
for (MachineBasicBlock::const_reverse_iterator I = BB->rbegin(),
|
||||
E = BB->rend(); I != E; ++I)
|
||||
if (I->getInstrDescriptor()->Flags & M_CLOBBERS_PRED)
|
||||
return true;
|
||||
return false;
|
||||
/// ValidSimple - Returns true if the 'true' block (along with its
|
||||
/// predecessor) forms a valid simple shape for ifcvt.
|
||||
bool IfConverter::ValidSimple(BBInfo &TrueBBI) const {
|
||||
return !blockAlwaysFallThrough(TrueBBI) &&
|
||||
TrueBBI.BrCond.size() == 0 && TrueBBI.BB->pred_size() == 1;
|
||||
}
|
||||
|
||||
/// ValidTriangle - Returns true if the 'true' and 'false' blocks paths (along
|
||||
/// ValidTriangle - Returns true if the 'true' and 'false' blocks (along
|
||||
/// with their common predecessor) forms a valid triangle shape for ifcvt.
|
||||
bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI) const {
|
||||
bool IfConverter::ValidTriangle(BBInfo &TrueBBI, BBInfo &FalseBBI,
|
||||
bool FalseBranch) const {
|
||||
if (TrueBBI.BB->pred_size() != 1)
|
||||
return false;
|
||||
|
||||
MachineBasicBlock *TTBB = TrueBBI.TrueBB;
|
||||
if (!TTBB && blockAlwaysFallThrough(TrueBBI)) {
|
||||
MachineBasicBlock *TExit = FalseBranch ? TrueBBI.FalseBB : TrueBBI.TrueBB;
|
||||
if (!TExit && blockAlwaysFallThrough(TrueBBI)) {
|
||||
MachineFunction::iterator I = TrueBBI.BB;
|
||||
if (++I == TrueBBI.BB->getParent()->end())
|
||||
return false;
|
||||
TTBB = I;
|
||||
TExit = I;
|
||||
}
|
||||
return TTBB && TTBB == FalseBBI.BB;
|
||||
return TExit && TExit == FalseBBI.BB;
|
||||
}
|
||||
|
||||
/// ValidDiamond - Returns true if the 'true' and 'false' blocks paths (along
|
||||
/// ValidDiamond - Returns true if the 'true' and 'false' blocks (along
|
||||
/// with their common predecessor) forms a valid diamond shape for ifcvt.
|
||||
bool IfConverter::ValidDiamond(BBInfo &TrueBBI, BBInfo &FalseBBI) const {
|
||||
// FIXME: Also look for fallthrough
|
||||
return (TrueBBI.TrueBB == FalseBBI.TrueBB &&
|
||||
TrueBBI.BB->pred_size() == 1 &&
|
||||
FalseBBI.BB->pred_size() == 1 &&
|
||||
!(TrueBBI.ModifyPredicate && FalseBBI.ModifyPredicate) &&
|
||||
!TrueBBI.FalseBB && !FalseBBI.FalseBB);
|
||||
}
|
||||
|
||||
/// StructuralAnalysis - Analyze the structure of the sub-CFG starting from
|
||||
/// AnalyzeBlock - Analyze the structure of the sub-CFG starting from
|
||||
/// the specified block. Record its successors and whether it looks like an
|
||||
/// if-conversion candidate.
|
||||
void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
|
||||
BBInfo &BBI = BBAnalysis[BB->getNumber()];
|
||||
|
||||
if (BBI.Kind == ICReAnalyze) {
|
||||
@ -286,7 +284,6 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
return; // Already analyzed.
|
||||
BBI.BB = BB;
|
||||
BBI.NonPredSize = std::distance(BB->begin(), BB->end());
|
||||
BBI.ModifyPredicate = BlockModifyPredicate(BB);
|
||||
}
|
||||
|
||||
// Look for 'root' of a simple (non-nested) triangle or diamond.
|
||||
@ -301,7 +298,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
if (BBI.TrueBB == BB || BBI.FalseBB == BB)
|
||||
return;
|
||||
|
||||
StructuralAnalysis(BBI.TrueBB);
|
||||
AnalyzeBlock(BBI.TrueBB);
|
||||
BBInfo &TrueBBI = BBAnalysis[BBI.TrueBB->getNumber()];
|
||||
|
||||
// No false branch. This BB must end with a conditional branch and a
|
||||
@ -310,7 +307,7 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
BBI.FalseBB = findFalseBlock(BB, BBI.TrueBB);
|
||||
assert(BBI.FalseBB && "Expected to find the fallthrough block!");
|
||||
|
||||
StructuralAnalysis(BBI.FalseBB);
|
||||
AnalyzeBlock(BBI.FalseBB);
|
||||
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
||||
|
||||
// If both paths are dead, then forget about it.
|
||||
@ -323,34 +320,11 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
// the CFG to form a triangle with the 'false' path.
|
||||
std::vector<MachineOperand> RevCond(BBI.BrCond);
|
||||
bool CanRevCond = !TII->ReverseBranchCondition(RevCond);
|
||||
if (FalseBBI.FalseBB) {
|
||||
if (TrueBBI.TrueBB && TrueBBI.TrueBB == BBI.FalseBB)
|
||||
return;
|
||||
std::vector<MachineOperand> Cond(BBI.BrCond);
|
||||
if (CanRevCond &&
|
||||
FalseBBI.TrueBB && FalseBBI.BB->pred_size() == 1 &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond, true)) {
|
||||
std::vector<MachineOperand> FalseCond(FalseBBI.BrCond);
|
||||
if (FalseBBI.TrueBB == BBI.TrueBB &&
|
||||
TII->SubsumesPredicate(FalseCond, BBI.BrCond)) {
|
||||
// Reverse 'true' and 'false' paths.
|
||||
ReverseBranchCondition(BBI);
|
||||
BBI.Kind = ICTriangle;
|
||||
FalseBBI.Kind = ICChild;
|
||||
} else if (FalseBBI.FalseBB == BBI.TrueBB &&
|
||||
!TII->ReverseBranchCondition(FalseCond) &&
|
||||
TII->SubsumesPredicate(FalseCond, BBI.BrCond)) {
|
||||
// Reverse 'false' block's 'true' and 'false' paths and then
|
||||
// reverse 'true' and 'false' paths.
|
||||
ReverseBranchCondition(FalseBBI);
|
||||
ReverseBranchCondition(BBI);
|
||||
BBI.Kind = ICTriangle;
|
||||
FalseBBI.Kind = ICChild;
|
||||
}
|
||||
}
|
||||
} else if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI) &&
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond)) {
|
||||
|
||||
if (CanRevCond && ValidDiamond(TrueBBI, FalseBBI) &&
|
||||
!(TrueBBI.ModifyPredicate && FalseBBI.ModifyPredicate) &&
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond) &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond)) {
|
||||
// Diamond:
|
||||
// EBB
|
||||
// / \_
|
||||
@ -364,50 +338,46 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
BBI.TailBB = TrueBBI.TrueBB;
|
||||
} else {
|
||||
// FIXME: Consider duplicating if BB is small.
|
||||
bool TryTriangle = ValidTriangle(TrueBBI, FalseBBI);
|
||||
bool TrySimple = !blockAlwaysFallThrough(TrueBBI) &&
|
||||
TrueBBI.BrCond.size() == 0 && TrueBBI.BB->pred_size() == 1;
|
||||
if ((TryTriangle || TrySimple) &&
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
|
||||
if (TryTriangle) {
|
||||
// Triangle:
|
||||
// EBB
|
||||
// | \_
|
||||
// | |
|
||||
// | TBB
|
||||
// | /
|
||||
// FBB
|
||||
BBI.Kind = ICTriangle;
|
||||
TrueBBI.Kind = ICChild;
|
||||
} else {
|
||||
// Simple (split, no rejoin):
|
||||
// EBB
|
||||
// | \_
|
||||
// | |
|
||||
// | TBB---> exit
|
||||
// |
|
||||
// FBB
|
||||
BBI.Kind = ICSimple;
|
||||
TrueBBI.Kind = ICChild;
|
||||
}
|
||||
} else if (FalseBBI.BrCond.size() == 0 && FalseBBI.BB->pred_size() == 1) {
|
||||
if (ValidTriangle(TrueBBI, FalseBBI) &&
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond, true)) {
|
||||
// Triangle:
|
||||
// EBB
|
||||
// | \_
|
||||
// | |
|
||||
// | TBB
|
||||
// | /
|
||||
// FBB
|
||||
BBI.Kind = ICTriangle;
|
||||
TrueBBI.Kind = ICChild;
|
||||
} else if (ValidSimple(TrueBBI) &&
|
||||
FeasibilityAnalysis(TrueBBI, BBI.BrCond)) {
|
||||
// Simple (split, no rejoin):
|
||||
// EBB
|
||||
// | \_
|
||||
// | |
|
||||
// | TBB---> exit
|
||||
// |
|
||||
// FBB
|
||||
BBI.Kind = ICSimple;
|
||||
TrueBBI.Kind = ICChild;
|
||||
} else if (CanRevCond) {
|
||||
// Try the other path...
|
||||
bool TryTriangle = ValidTriangle(FalseBBI, TrueBBI);
|
||||
bool TrySimple = !blockAlwaysFallThrough(FalseBBI);
|
||||
if (TryTriangle || TrySimple) {
|
||||
std::vector<MachineOperand> RevCond(BBI.BrCond);
|
||||
if (!TII->ReverseBranchCondition(RevCond) &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond)) {
|
||||
if (TryTriangle) {
|
||||
// Reverse 'true' and 'false' paths.
|
||||
ReverseBranchCondition(BBI);
|
||||
BBI.Kind = ICTriangle;
|
||||
FalseBBI.Kind = ICChild;
|
||||
} else {
|
||||
BBI.Kind = ICSimpleFalse;
|
||||
FalseBBI.Kind = ICChild;
|
||||
}
|
||||
}
|
||||
if (ValidTriangle(FalseBBI, TrueBBI) &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond, true)) {
|
||||
// Reverse 'true' and 'false' paths.
|
||||
ReverseBranchCondition(BBI);
|
||||
BBI.Kind = ICTriangle;
|
||||
FalseBBI.Kind = ICChild;
|
||||
} else if (ValidTriangle(FalseBBI, TrueBBI, true) &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond, true, true)) {
|
||||
ReverseBranchCondition(FalseBBI);
|
||||
ReverseBranchCondition(BBI);
|
||||
BBI.Kind = ICTriangle;
|
||||
FalseBBI.Kind = ICChild;
|
||||
} else if (ValidSimple(FalseBBI) &&
|
||||
FeasibilityAnalysis(FalseBBI, RevCond)) {
|
||||
BBI.Kind = ICSimpleFalse;
|
||||
FalseBBI.Kind = ICChild;
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -418,11 +388,10 @@ void IfConverter::StructuralAnalysis(MachineBasicBlock *BB) {
|
||||
/// cases, that means all the instructions in the block has M_PREDICABLE flag.
|
||||
/// Also checks if the block contains any instruction which can clobber a
|
||||
/// predicate (e.g. condition code register). If so, the block is not
|
||||
/// predicable unless it's the last instruction. If IgnoreTerm is true then
|
||||
/// all the terminator instructions are skipped.
|
||||
/// predicable unless it's the last instruction.
|
||||
bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
|
||||
std::vector<MachineOperand> &Cond,
|
||||
bool IgnoreTerm) {
|
||||
std::vector<MachineOperand> &Pred,
|
||||
bool isTriangle, bool RevBranch) {
|
||||
// If the block is dead, or it is going to be the entry block of a sub-CFG
|
||||
// that will be if-converted, then it cannot be predicated.
|
||||
if (BBI.Kind != ICNotAnalyzed &&
|
||||
@ -436,13 +405,46 @@ bool IfConverter::FeasibilityAnalysis(BBInfo &BBI,
|
||||
|
||||
// If it is already predicated, check if its predicate subsumes the new
|
||||
// predicate.
|
||||
if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Cond))
|
||||
if (BBI.Predicate.size() && !TII->SubsumesPredicate(BBI.Predicate, Pred))
|
||||
return false;
|
||||
|
||||
bool SeenPredMod = false;
|
||||
bool SeenCondBr = false;
|
||||
for (MachineBasicBlock::iterator I = BBI.BB->begin(), E = BBI.BB->end();
|
||||
I != E; ++I) {
|
||||
if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
|
||||
continue;
|
||||
const TargetInstrDescriptor *TID = I->getInstrDescriptor();
|
||||
if (SeenPredMod) {
|
||||
// Predicate modification instruction should end the block (except for
|
||||
// already predicated instructions and end of block branches).
|
||||
if (!TII->isPredicated(I)) {
|
||||
// This is the 'true' block of a triangle, i.e. its 'true' block is
|
||||
// the same as the 'false' block of the entry. So false positive
|
||||
// is ok.
|
||||
if (isTriangle && !SeenCondBr && BBI.IsAnalyzable &&
|
||||
(TID->Flags & M_BRANCH_FLAG) != 0 &&
|
||||
(TID->Flags & M_BARRIER_FLAG) == 0) {
|
||||
// This is the first conditional branch, test predicate subsumsion.
|
||||
std::vector<MachineOperand> RevPred(Pred);
|
||||
std::vector<MachineOperand> Cond(BBI.BrCond);
|
||||
if (RevBranch) {
|
||||
if (TII->ReverseBranchCondition(Cond))
|
||||
return false;
|
||||
}
|
||||
if (TII->ReverseBranchCondition(RevPred) ||
|
||||
!TII->SubsumesPredicate(Cond, RevPred))
|
||||
return false;
|
||||
SeenCondBr = true;
|
||||
continue; // Conditional branches is not predicable.
|
||||
}
|
||||
return false;
|
||||
}
|
||||
}
|
||||
|
||||
if (TID->Flags & M_CLOBBERS_PRED) {
|
||||
BBI.ModifyPredicate = true;
|
||||
SeenPredMod = true;
|
||||
}
|
||||
|
||||
if (!I->isPredicable())
|
||||
return false;
|
||||
}
|
||||
@ -488,7 +490,7 @@ bool IfConverter::AnalyzeBlocks(MachineFunction &MF,
|
||||
for (idf_ext_iterator<MachineBasicBlock*> I=idf_ext_begin(Roots[i],Visited),
|
||||
E = idf_ext_end(Roots[i], Visited); I != E; ++I) {
|
||||
MachineBasicBlock *BB = *I;
|
||||
StructuralAnalysis(BB);
|
||||
AnalyzeBlock(BB);
|
||||
BBInfo &BBI = BBAnalysis[BB->getNumber()];
|
||||
switch (BBI.Kind) {
|
||||
case ICSimple:
|
||||
@ -560,23 +562,23 @@ bool IfConverter::IfConvertSimple(BBInfo &BBI) {
|
||||
// to the 'false' branch.
|
||||
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
||||
MergeBlocks(BBI, *CvtBBI);
|
||||
BBI.BB->removeSuccessor(CvtBBI->BB);
|
||||
|
||||
bool IterIfcvt = true;
|
||||
if (!isNextBlock(BBI.BB, NextBBI->BB)) {
|
||||
InsertUncondBranch(BBI.BB, NextBBI->BB, TII);
|
||||
BBI.hasFallThrough = false;
|
||||
if (BBI.ModifyPredicate)
|
||||
// Now ifcvt'd block will look like this:
|
||||
// BB:
|
||||
// ...
|
||||
// t, f = cmp
|
||||
// if t op
|
||||
// b BBf
|
||||
//
|
||||
// We cannot further ifcvt this block because the unconditional branch
|
||||
// will have to be predicated on the new condition, that will not be
|
||||
// available if cmp executes.
|
||||
IterIfcvt = false;
|
||||
// Now ifcvt'd block will look like this:
|
||||
// BB:
|
||||
// ...
|
||||
// t, f = cmp
|
||||
// if t op
|
||||
// b BBf
|
||||
//
|
||||
// We cannot further ifcvt this block because the unconditional branch
|
||||
// will have to be predicated on the new condition, that will not be
|
||||
// available if cmp executes.
|
||||
IterIfcvt = false;
|
||||
}
|
||||
std::copy(Cond.begin(), Cond.end(), std::back_inserter(BBI.Predicate));
|
||||
|
||||
@ -610,45 +612,34 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
|
||||
TII->InsertBranch(*BBI.TrueBB, TrueBBI.FalseBB, NULL, RevCond);
|
||||
}
|
||||
|
||||
// Join the 'true' and 'false' blocks if the 'false' block has no other
|
||||
// predecessors. Otherwise, add a unconditional branch from 'true' to 'false'.
|
||||
// Now merge the entry of the triangle with the true block.
|
||||
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
||||
MergeBlocks(BBI, TrueBBI);
|
||||
|
||||
// Merge in the 'false' block if the 'false' block has no other
|
||||
// predecessors. Otherwise, add a unconditional branch from to 'false'.
|
||||
BBInfo &FalseBBI = BBAnalysis[BBI.FalseBB->getNumber()];
|
||||
bool FalseBBDead = false;
|
||||
bool IterIfcvt = true;
|
||||
bool isFallThrough = isNextBlock(TrueBBI.BB, FalseBBI.BB);
|
||||
bool isFallThrough = isNextBlock(BBI.BB, FalseBBI.BB);
|
||||
if (!isFallThrough) {
|
||||
// Only merge them if the true block does not fallthrough to the false
|
||||
// block. By not merging them, we make it possible to iteratively
|
||||
// ifcvt the blocks.
|
||||
if (!HasEarlyExit && FalseBBI.BB->pred_size() == 2) {
|
||||
MergeBlocks(TrueBBI, FalseBBI);
|
||||
if (!HasEarlyExit && FalseBBI.BB->pred_size() == 1) {
|
||||
MergeBlocks(BBI, FalseBBI);
|
||||
FalseBBDead = true;
|
||||
// Mixed predicated and unpredicated code. This cannot be iteratively
|
||||
// predicated.
|
||||
IterIfcvt = false;
|
||||
} else {
|
||||
InsertUncondBranch(TrueBBI.BB, FalseBBI.BB, TII);
|
||||
InsertUncondBranch(BBI.BB, FalseBBI.BB, TII);
|
||||
TrueBBI.hasFallThrough = false;
|
||||
if (BBI.ModifyPredicate || TrueBBI.ModifyPredicate)
|
||||
// Now ifcvt'd block will look like this:
|
||||
// BB:
|
||||
// ...
|
||||
// t, f = cmp
|
||||
// if t op
|
||||
// b BBf
|
||||
//
|
||||
// We cannot further ifcvt this block because the unconditional branch will
|
||||
// have to be predicated on the new condition, that will not be available
|
||||
// if cmp executes.
|
||||
IterIfcvt = false;
|
||||
}
|
||||
// Mixed predicated and unpredicated code. This cannot be iteratively
|
||||
// predicated.
|
||||
IterIfcvt = false;
|
||||
}
|
||||
|
||||
// Now merge the entry of the triangle with the true block.
|
||||
BBI.NonPredSize -= TII->RemoveBranch(*BBI.BB);
|
||||
MergeBlocks(BBI, TrueBBI);
|
||||
// Remove entry to false edge if false block is merged in as well.
|
||||
if (FalseBBDead && BBI.BB->isSuccessor(FalseBBI.BB))
|
||||
if (FalseBBDead)
|
||||
BBI.BB->removeSuccessor(FalseBBI.BB);
|
||||
std::copy(BBI.BrCond.begin(), BBI.BrCond.end(),
|
||||
std::back_inserter(BBI.Predicate));
|
||||
|
Loading…
Reference in New Issue
Block a user