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Do not dup malloc, vector instructions, etc. Throttle the default theshold way down. 

llvm-svn: 51183
This commit is contained in:
Evan Cheng 2008-05-16 07:55:50 +00:00
parent c7d6eceb69
commit 173a53f87c
1 changed files with 15 additions and 5 deletions
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20
llvm/lib/Transforms/Scalar/TailDuplication.cpp
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@ -39,8 +39,9 @@ using namespace llvm;
STATISTIC(NumEliminated, "Number of unconditional branches eliminated");
static cl::opt<unsigned>
Threshold("taildup-threshold", cl::desc("Max block size to tail duplicate"),
cl::init(6), cl::Hidden);
TailDupThreshold("taildup-threshold",
cl::desc("Max block size to tail duplicate"),
cl::init(1), cl::Hidden);
namespace {
class VISIBILITY_HIDDEN TailDup : public FunctionPass {
@ -50,7 +51,7 @@ namespace {
TailDup() : FunctionPass((intptr_t)&ID) {}
private:
inline bool shouldEliminateUnconditionalBranch(TerminatorInst *TI);
inline bool shouldEliminateUnconditionalBranch(TerminatorInst *, unsigned);
inline void eliminateUnconditionalBranch(BranchInst *BI);
SmallPtrSet<BasicBlock*, 4> CycleDetector;
};
@ -70,7 +71,8 @@ bool TailDup::runOnFunction(Function &F) {
bool Changed = false;
CycleDetector.clear();
for (Function::iterator I = F.begin(), E = F.end(); I != E; ) {
if (shouldEliminateUnconditionalBranch(I->getTerminator())) {
if (shouldEliminateUnconditionalBranch(I->getTerminator(),
TailDupThreshold)) {
eliminateUnconditionalBranch(cast<BranchInst>(I->getTerminator()));
Changed = true;
} else {
@ -90,7 +92,8 @@ bool TailDup::runOnFunction(Function &F) {
/// We don't count PHI nodes in the count since they will be removed when the
/// contents of the block are copied over.
///
bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI) {
bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI,
unsigned Threshold) {
BranchInst *BI = dyn_cast<BranchInst>(TI);
if (!BI || !BI->isUnconditional()) return false; // Not an uncond branch!
@ -124,6 +127,13 @@ bool TailDup::shouldEliminateUnconditionalBranch(TerminatorInst *TI) {
// Don't tail duplicate call instructions. They are very large compared to
// other instructions.
if (isa<CallInst>(I) || isa<InvokeInst>(I)) return false;
// Allso alloca and malloc.
if (isa<AllocationInst>(I)) return false;
// Some vector instructions can expand into a number of instructions.
if (isa<ShuffleVectorInst>(I) || isa<ExtractElementInst>(I) ||
isa<InsertElementInst>(I)) return false;
// Only count instructions that are not debugger intrinsics.
if (!isa<DbgInfoIntrinsic>(I)) ++Size;