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Fairly major change: emit fixed sized allocas in the entry block as a variable,

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instead of a variable pointer and an alloca.  All accesses to the variable then
use the address-of operator to access it.  This plays better with the internal
GCC code generation phases, which bail early on functions which contain allocas.
It also makes the code a bit easier to read.

llvm-svn: 6734
This commit is contained in:
Chris Lattner 2003-06-17 04:39:14 +00:00
parent 2b01ee820e
commit 44689264b2
1 changed files with 26 additions and 6 deletions
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30
lib/CWriter/Writer.cpp
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@ -97,6 +97,20 @@ namespace {
return I.getParent() == cast<Instruction>(I.use_back())->getParent();
}
// isDirectAlloca - Define fixed sized allocas in the entry block as direct
// variables which are accessed with the & operator. This causes GCC to
// generate significantly better code than to emit alloca calls directly.
//
static const AllocaInst *isDirectAlloca(const Value *V) {
const AllocaInst *AI = dyn_cast<AllocaInst>(V);
if (!AI) return false;
if (AI->isArrayAllocation())
return 0; // FIXME: we can also inline fixed size array allocas!
if (AI->getParent() != &AI->getParent()->getParent()->getEntryNode())
return 0;
return AI;
}
// Instruction visitation functions
friend class InstVisitor<CWriter>;
@ -463,7 +477,7 @@ void CWriter::printConstant(Constant *CPV) {
void CWriter::writeOperandInternal(Value *Operand) {
if (Instruction *I = dyn_cast<Instruction>(Operand))
if (isInlinableInst(*I)) {
if (isInlinableInst(*I) && !isDirectAlloca(I)) {
// Should we inline this instruction to build a tree?
Out << "(";
visit(*I);
@ -483,12 +497,12 @@ void CWriter::writeOperandInternal(Value *Operand) {
}
void CWriter::writeOperand(Value *Operand) {
if (isa<GlobalVariable>(Operand))
if (isa<GlobalVariable>(Operand) || isDirectAlloca(Operand))
Out << "(&"; // Global variables are references as their addresses by llvm
writeOperandInternal(Operand);
if (isa<GlobalVariable>(Operand))
if (isa<GlobalVariable>(Operand) || isDirectAlloca(Operand))
Out << ")";
}
@ -792,7 +806,11 @@ void CWriter::printFunction(Function *F) {
// print local variable information for the function
for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
if ((*I)->getType() != Type::VoidTy && !isInlinableInst(**I)) {
if (const AllocaInst *AI = isDirectAlloca(*I)) {
Out << " ";
printType(Out, AI->getAllocatedType(), getValueName(AI));
Out << "; /* Address exposed local */\n";
} else if ((*I)->getType() != Type::VoidTy && !isInlinableInst(**I)) {
Out << " ";
printType(Out, (*I)->getType(), getValueName(*I));
Out << ";\n";
@ -856,7 +874,7 @@ void CWriter::printFunction(Function *F) {
// Output all of the instructions in the basic block...
for (BasicBlock::iterator II = BB->begin(), E = --BB->end(); II != E; ++II){
if (!isInlinableInst(*II)) {
if (!isInlinableInst(*II) && !isDirectAlloca(II)) {
if (II->getType() != Type::VoidTy)
outputLValue(II);
else
@ -1132,6 +1150,8 @@ void CWriter::printIndexingExpression(Value *Ptr, User::op_iterator I,
} else if (ConstantPointerRef *CPR = dyn_cast<ConstantPointerRef>(Ptr)) {
HasImplicitAddress = true;
Ptr = CPR->getValue(); // Get to the global...
} else if (isDirectAlloca(Ptr)) {
HasImplicitAddress = true;
}
if (I == E) {