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isBlockPredicable() always ignore terminal instructions; add comments.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37126 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Evan Cheng 2007-05-16 21:54:37 +00:00
parent 3f8602cf20
commit d6ddc308f0
1 changed files with 23 additions and 13 deletions
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36
lib/CodeGen/IfConversion.cpp
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@ -68,8 +68,7 @@ namespace {
std::vector<int> &Candidates);
bool IfConvertDiamond(BBInfo &BBI);
bool IfConvertTriangle(BBInfo &BBI);
bool isBlockPredicable(MachineBasicBlock *BB,
bool IgnoreTerm = false) const;
bool isBlockPredicable(MachineBasicBlock *BB) const;
void PredicateBlock(MachineBasicBlock *BB,
std::vector<MachineOperand> &Cond,
bool IgnoreTerm = false);
@ -134,15 +133,19 @@ void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
if (TII->AnalyzeBranch(*BB, BBI.TBB, BBI.FBB, BBI.Cond)
|| !BBI.TBB || BBI.Cond.size() == 0)
return;
// Can't do it if 'true' block is already marked as to be if-converted.
AnalyzeBlock(BBI.TBB);
BBInfo &TBBI = BBAnalysis[BBI.TBB->getNumber()];
if (TBBI.Kind != ICNotClassfied)
return;
// No false branch. This BB must end with a conditional branch and a
// fallthrough.
if (!BBI.FBB)
BBI.FBB = findFalseBlock(BB, BBI.TBB);
assert(BBI.FBB && "Expected to find the fallthrough block!");
// Can't do it if 'false' block is already marked as to be if-converted.
AnalyzeBlock(BBI.FBB);
BBInfo &FBBI = BBAnalysis[BBI.FBB->getNumber()];
if (FBBI.Kind != ICNotClassfied)
@ -178,6 +181,8 @@ void IfConverter::AnalyzeBlock(MachineBasicBlock *BB) {
return;
}
/// InitialFunctionAnalysis - Analyze all blocks and find entries for all
/// if-conversion candidates.
void IfConverter::InitialFunctionAnalysis(MachineFunction &MF,
std::vector<int> &Candidates) {
for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
@ -189,8 +194,10 @@ void IfConverter::InitialFunctionAnalysis(MachineFunction &MF,
}
}
/// IfConvertTriangle - If convert a triangle sub-CFG.
///
bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
if (isBlockPredicable(BBI.TBB, true)) {
if (isBlockPredicable(BBI.TBB)) {
// Predicate the 'true' block after removing its branch.
TII->RemoveBranch(*BBI.TBB);
PredicateBlock(BBI.TBB, BBI.Cond);
@ -213,9 +220,10 @@ bool IfConverter::IfConvertTriangle(BBInfo &BBI) {
return false;
}
/// IfConvertDiamond - If convert a diamond sub-CFG.
///
bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
if (isBlockPredicable(BBI.TBB, true) &&
isBlockPredicable(BBI.FBB, true)) {
if (isBlockPredicable(BBI.TBB) && isBlockPredicable(BBI.FBB)) {
std::vector<MachineInstr*> Dups;
if (!BBI.CMBB) {
// No common merge block. Check if the terminators (e.g. return) are
@ -230,7 +238,8 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
++TT;
++FT;
}
// One of the two pathes have more terminators, make sure they are all
// predicable.
while (TT != BBI.TBB->end())
if (!TT->isPredicable())
return false; // Can't if-convert. Abort!
@ -272,13 +281,11 @@ bool IfConverter::IfConvertDiamond(BBInfo &BBI) {
/// isBlockPredicable - Returns true if the block is predicable. In most
/// cases, that means all the instructions in the block has M_PREDICABLE flag.
/// If IgnoreTerm is true, assume all the terminator instructions can be
/// converted or deleted.
bool IfConverter::isBlockPredicable(MachineBasicBlock *BB,
bool IgnoreTerm) const {
/// It assume all the terminator instructions can be converted or deleted.
bool IfConverter::isBlockPredicable(MachineBasicBlock *BB) const {
for (MachineBasicBlock::iterator I = BB->begin(), E = BB->end();
I != E; ++I) {
if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
if (TII->isTerminatorInstr(I->getOpcode()))
continue;
if (!I->isPredicable())
return false;
@ -295,7 +302,10 @@ void IfConverter::PredicateBlock(MachineBasicBlock *BB,
I != E; ++I) {
if (IgnoreTerm && TII->isTerminatorInstr(I->getOpcode()))
continue;
TII->PredicateInstruction(&*I, Cond);
if (!TII->PredicateInstruction(&*I, Cond)) {
cerr << "Unable to predication " << *I << "!\n";
abort();
}
}
}