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Clean up the FFS optimization code, and make it correctly create the appropriate

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unsigned llvm.cttz.* intrinsic, fixing the 2005-05-11-Popcount-ffs-fls regression
last night.

llvm-svn: 25398
This commit is contained in:
Chris Lattner 2006-01-17 18:27:17 +00:00
parent 0c4202b0ba
commit ddbf4fba37
1 changed files with 43 additions and 41 deletions
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84
lib/Transforms/IPO/SimplifyLibCalls.cpp
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@ -1810,69 +1810,71 @@ public:
/// optimization is to compute the result at compile time if the argument is
/// a constant.
/// @brief Simplify the ffs library function.
struct FFSOptimization : public LibCallOptimization
{
struct FFSOptimization : public LibCallOptimization {
protected:
/// @brief Subclass Constructor
FFSOptimization(const char* funcName, const char* description)
: LibCallOptimization(funcName, description)
{}
: LibCallOptimization(funcName, description) {}
public:
/// @brief Default Constructor
FFSOptimization() : LibCallOptimization("ffs",
"Number of 'ffs' calls simplified") {}
/// @brief Make sure that the "fputs" function has the right prototype
virtual bool ValidateCalledFunction(const Function* f, SimplifyLibCalls& SLC)
{
/// @brief Make sure that the "ffs" function has the right prototype
virtual bool ValidateCalledFunction(const Function *F, SimplifyLibCalls &SLC){
// Just make sure this has 2 arguments
return (f->arg_size() == 1 && f->getReturnType() == Type::IntTy);
return F->arg_size() == 1 && F->getReturnType() == Type::IntTy;
}
/// @brief Perform the ffs optimization.
virtual bool OptimizeCall(CallInst* ci, SimplifyLibCalls& SLC)
{
if (ConstantInt* CI = dyn_cast<ConstantInt>(ci->getOperand(1)))
{
virtual bool OptimizeCall(CallInst *TheCall, SimplifyLibCalls &SLC) {
if (ConstantInt *CI = dyn_cast<ConstantInt>(TheCall->getOperand(1))) {
// ffs(cnst) -> bit#
// ffsl(cnst) -> bit#
// ffsll(cnst) -> bit#
uint64_t val = CI->getRawValue();
int result = 0;
while (val != 0) {
result +=1;
if (val&1)
break;
val >>= 1;
if (val) {
++result;
while ((val & 1) == 0) {
++result;
val >>= 1;
}
}
ci->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
ci->eraseFromParent();
TheCall->replaceAllUsesWith(ConstantSInt::get(Type::IntTy, result));
TheCall->eraseFromParent();
return true;
}
// ffs(x) -> ( x == 0 ? 0 : llvm.cttz(x)+1)
// ffsl(x) -> ( x == 0 ? 0 : llvm.cttz(x)+1)
// ffsll(x) -> ( x == 0 ? 0 : llvm.cttz(x)+1)
const Type* arg_type = ci->getOperand(1)->getType();
std::vector<const Type*> args;
args.push_back(arg_type);
FunctionType* llvm_cttz_type = FunctionType::get(arg_type,args,false);
Function* F =
SLC.getModule()->getOrInsertFunction("llvm.cttz",llvm_cttz_type);
std::string inst_name(ci->getName()+".ffs");
Instruction* call =
new CallInst(F, ci->getOperand(1), inst_name, ci);
if (arg_type != Type::IntTy)
call = new CastInst(call, Type::IntTy, inst_name, ci);
BinaryOperator* add = BinaryOperator::createAdd(call,
ConstantSInt::get(Type::IntTy,1), inst_name, ci);
SetCondInst* eq = new SetCondInst(Instruction::SetEQ,ci->getOperand(1),
ConstantSInt::get(ci->getOperand(1)->getType(),0),inst_name,ci);
SelectInst* select = new SelectInst(eq,ConstantSInt::get(Type::IntTy,0),add,
inst_name,ci);
ci->replaceAllUsesWith(select);
ci->eraseFromParent();
// ffs(x) -> x == 0 ? 0 : llvm.cttz(x)+1
// ffsl(x) -> x == 0 ? 0 : llvm.cttz(x)+1
// ffsll(x) -> x == 0 ? 0 : llvm.cttz(x)+1
const Type *ArgType = TheCall->getOperand(1)->getType();
ArgType = ArgType->getUnsignedVersion();
const char *CTTZName;
switch (ArgType->getTypeID()) {
default: assert(0 && "Unknown unsigned type!");
case Type::UByteTyID : CTTZName = "llvm.cttz.i8" ; break;
case Type::UShortTyID: CTTZName = "llvm.cttz.i16"; break;
case Type::UIntTyID : CTTZName = "llvm.cttz.i32"; break;
case Type::ULongTyID : CTTZName = "llvm.cttz.i64"; break;
}
Function *F = SLC.getModule()->getOrInsertFunction(CTTZName, ArgType,
ArgType, NULL);
Value *V = new CastInst(TheCall->getOperand(1), ArgType, "tmp", TheCall);
Value *V2 = new CallInst(F, V, "tmp", TheCall);
V2 = new CastInst(V2, Type::IntTy, "tmp", TheCall);
V2 = BinaryOperator::createAdd(V2, ConstantSInt::get(Type::IntTy, 1),
"tmp", TheCall);
Value *Cond =
BinaryOperator::createSetEQ(V, Constant::getNullValue(V->getType()),
"tmp", TheCall);
V2 = new SelectInst(Cond, ConstantInt::get(Type::IntTy, 0), V2,
TheCall->getName(), TheCall);
TheCall->replaceAllUsesWith(V2);
TheCall->eraseFromParent();
return true;
}
} FFSOptimizer;