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Make tail merging the default, except on powerPC. There was no prior art

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for a target-dependent default with a command-line override; this way
should be generally usable.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@37285 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dale Johannesen
2007-05-22 17:14:46 +00:00
parent 9621921acb
commit 81da02b553
8 changed files with 69 additions and 7 deletions
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17
lib/CodeGen/BranchFolding.cpp
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@ -35,12 +35,19 @@ using namespace llvm;
STATISTIC(NumDeadBlocks, "Number of dead blocks removed");
STATISTIC(NumBranchOpts, "Number of branches optimized");
STATISTIC(NumTailMerge , "Number of block tails merged");
static cl::opt<bool> EnableTailMerge("enable-tail-merge", cl::Hidden);
static cl::opt<cl::boolOrDefault> FlagEnableTailMerge("enable-tail-merge",
cl::init(cl::BOU_UNSET), cl::Hidden);
namespace {
struct BranchFolder : public MachineFunctionPass {
static char ID;
BranchFolder() : MachineFunctionPass((intptr_t)&ID) {}
BranchFolder(bool defaultEnableTailMerge) :
MachineFunctionPass((intptr_t)&ID) {
switch (FlagEnableTailMerge) {
case cl::BOU_UNSET: EnableTailMerge = defaultEnableTailMerge; break;
case cl::BOU_TRUE: EnableTailMerge = true; break;
case cl::BOU_FALSE: EnableTailMerge = false; break;
}
}
virtual bool runOnMachineFunction(MachineFunction &MF);
virtual const char *getPassName() const { return "Control Flow Optimizer"; }
@ -49,6 +56,7 @@ namespace {
bool MadeChange;
private:
// Tail Merging.
bool EnableTailMerge;
bool TailMergeBlocks(MachineFunction &MF);
bool TryMergeBlocks(MachineBasicBlock* SuccBB,
MachineBasicBlock* PredBB);
@ -79,7 +87,8 @@ static bool CorrectExtraCFGEdges(MachineBasicBlock &MBB,
bool isCond,
MachineFunction::iterator FallThru);
FunctionPass *llvm::createBranchFoldingPass() { return new BranchFolder(); }
FunctionPass *llvm::createBranchFoldingPass(bool DefaultEnableTailMerge) {
return new BranchFolder(DefaultEnableTailMerge); }
/// RemoveDeadBlock - Remove the specified dead machine basic block from the
/// function, updating the CFG.