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Refactor code a little bit, eliminating the gratuitous InstVisitor, which

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should make subsequent changes simpler.  This also allows us to hoist vaarg
and vanext instructions


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10342 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner 2003-12-09 19:32:44 +00:00
parent 92094b4d92
commit ed6dfc2856
1 changed files with 43 additions and 41 deletions
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84
lib/Transforms/Scalar/LICM.cpp
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@ -41,7 +41,6 @@
#include "llvm/Instructions.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/CFG.h"
#include "Support/CommandLine.h"
#include "Support/Debug.h"
@ -60,7 +59,7 @@ namespace {
Statistic<> NumPromoted("licm",
"Number of memory locations promoted to registers");
struct LICM : public FunctionPass, public InstVisitor<LICM> {
struct LICM : public FunctionPass {
virtual bool runOnFunction(Function &F);
/// This transformation requires natural loop information & requires that
@ -137,6 +136,7 @@ namespace {
return !CurLoop->contains(I->getParent());
return true; // All non-instructions are loop invariant
}
bool isLoopInvariantInst(Instruction &Inst);
/// PromoteValuesInLoop - Look at the stores in the loop and promote as many
/// to scalars as we can.
@ -152,32 +152,6 @@ namespace {
void findPromotableValuesInLoop(
std::vector<std::pair<AllocaInst*, Value*> > &PromotedValues,
std::map<Value*, AllocaInst*> &Val2AlMap);
/// Instruction visitation handlers... these basically control whether or
/// not the specified instruction types are hoisted.
///
friend class InstVisitor<LICM>;
void visitBinaryOperator(Instruction &I) {
if (isLoopInvariant(I.getOperand(0)) &&
isLoopInvariant(I.getOperand(1)) && SafeToHoist(I))
hoist(I);
}
void visitCastInst(CastInst &CI) {
Instruction &I = (Instruction&)CI;
if (isLoopInvariant(I.getOperand(0)) && SafeToHoist(CI)) hoist(I);
}
void visitShiftInst(ShiftInst &I) { visitBinaryOperator((Instruction&)I); }
void visitLoadInst(LoadInst &LI);
void visitGetElementPtrInst(GetElementPtrInst &GEPI) {
Instruction &I = (Instruction&)GEPI;
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
if (!isLoopInvariant(I.getOperand(i))) return;
if(SafeToHoist(GEPI))
hoist(I);
}
};
RegisterOpt<LICM> X("licm", "Loop Invariant Code Motion");
@ -202,7 +176,7 @@ bool LICM::runOnFunction(Function &) {
for (std::vector<Loop*>::const_iterator I = TopLevelLoops.begin(),
E = TopLevelLoops.end(); I != E; ++I) {
AliasSetTracker AST(*AA);
LICM::visitLoop(*I, AST);
visitLoop(*I, AST);
}
return Changed;
}
@ -215,7 +189,7 @@ void LICM::visitLoop(Loop *L, AliasSetTracker &AST) {
for (std::vector<Loop*>::const_iterator I = L->getSubLoops().begin(),
E = L->getSubLoops().end(); I != E; ++I) {
AliasSetTracker SubAST(*AA);
LICM::visitLoop(*I, SubAST);
visitLoop(*I, SubAST);
// Incorporate information about the subloops into this loop...
AST.add(SubAST);
@ -265,20 +239,53 @@ void LICM::visitLoop(Loop *L, AliasSetTracker &AST) {
///
void LICM::HoistRegion(DominatorTree::Node *N) {
assert(N != 0 && "Null dominator tree node?");
BasicBlock *BB = N->getBlock();
// If this subregion is not in the top level loop at all, exit.
if (!CurLoop->contains(N->getBlock())) return;
if (!CurLoop->contains(BB)) return;
// Only need to hoist the contents of this block if it is not part of a
// subloop (which would already have been hoisted)
if (!inSubLoop(N->getBlock()))
visit(*N->getBlock());
if (!inSubLoop(BB))
for (BasicBlock::iterator I = BB->begin(), E = --BB->end(); I != E; ) {
Instruction &Inst = *I++;
if (isLoopInvariantInst(Inst) && SafeToHoist(Inst))
hoist(Inst);
}
const std::vector<DominatorTree::Node*> &Children = N->getChildren();
for (unsigned i = 0, e = Children.size(); i != e; ++i)
HoistRegion(Children[i]);
}
bool LICM::isLoopInvariantInst(Instruction &I) {
assert(!isa<TerminatorInst>(I) && "Can't hoist terminator instructions!");
// We can only hoist simple expressions...
if (!isa<BinaryOperator>(I) && !isa<ShiftInst>(I) && !isa<LoadInst>(I) &&
!isa<GetElementPtrInst>(I) && !isa<CastInst>(I) && !isa<VANextInst>(I) &&
!isa<VAArgInst>(I))
return false;
// The instruction is loop invariant if all of its operands are loop-invariant
for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
if (!isLoopInvariant(I.getOperand(i)))
return false;
// Loads have extra constraints we have to verify before we can hoist them.
if (LoadInst *LI = dyn_cast<LoadInst>(&I)) {
if (LI->isVolatile())
return false; // Don't hoist volatile loads!
// Don't hoist loads which have may-aliased stores in loop.
if (pointerInvalidatedByLoop(I.getOperand(0)))
return false;
}
// If we got this far, the instruction is loop invariant!
return true;
}
/// hoist - When an instruction is found to only use loop invariant operands
/// that is safe to hoist, this instruction is called to do the dirty work.
@ -288,6 +295,9 @@ void LICM::hoist(Instruction &Inst) {
WriteAsOperand(std::cerr, Preheader, false);
std::cerr << ": " << Inst);
if (isa<LoadInst>(Inst))
++NumHoistedLoads;
// Remove the instruction from its current basic block... but don't delete the
// instruction.
Inst.getParent()->getInstList().remove(&Inst);
@ -344,14 +354,6 @@ bool LICM::SafeToHoist(Instruction &Inst) {
}
void LICM::visitLoadInst(LoadInst &LI) {
if (isLoopInvariant(LI.getOperand(0)) && !LI.isVolatile() &&
!pointerInvalidatedByLoop(LI.getOperand(0)) && SafeToHoist(LI)) {
hoist(LI);
++NumHoistedLoads;
}
}
/// PromoteValuesInLoop - Try to promote memory values to scalars by sinking
/// stores out of the loop and moving loads to before the loop. We do this by
/// looping over the stores in the loop, looking for stores to Must pointers