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instcombine: Migrate strstr optimizations

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This patch migrates the strstr optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167682 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Meador Inge
2012-11-11 03:51:48 +00:00
parent b69bf6be1b
commit 6e1591a5d5
5 changed files with 166 additions and 148 deletions
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80
lib/Transforms/Utils/SimplifyLibCalls.cpp
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@ -86,6 +86,20 @@ static bool isOnlyUsedInZeroEqualityComparison(Value *V) {
return true;
}
/// isOnlyUsedInEqualityComparison - Return true if it is only used in equality
/// comparisons with With.
static bool isOnlyUsedInEqualityComparison(Value *V, Value *With) {
for (Value::use_iterator UI = V->use_begin(), E = V->use_end();
UI != E; ++UI) {
if (ICmpInst *IC = dyn_cast<ICmpInst>(*UI))
if (IC->isEquality() && IC->getOperand(1) == With)
continue;
// Unknown instruction.
return false;
}
return true;
}
//===----------------------------------------------------------------------===//
// Fortified Library Call Optimizations
//===----------------------------------------------------------------------===//
@ -836,6 +850,70 @@ struct StrCSpnOpt : public LibCallOptimization {
}
};
struct StrStrOpt : public LibCallOptimization {
virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
FunctionType *FT = Callee->getFunctionType();
if (FT->getNumParams() != 2 ||
!FT->getParamType(0)->isPointerTy() ||
!FT->getParamType(1)->isPointerTy() ||
!FT->getReturnType()->isPointerTy())
return 0;
// fold strstr(x, x) -> x.
if (CI->getArgOperand(0) == CI->getArgOperand(1))
return B.CreateBitCast(CI->getArgOperand(0), CI->getType());
// fold strstr(a, b) == a -> strncmp(a, b, strlen(b)) == 0
if (TD && isOnlyUsedInEqualityComparison(CI, CI->getArgOperand(0))) {
Value *StrLen = EmitStrLen(CI->getArgOperand(1), B, TD, TLI);
if (!StrLen)
return 0;
Value *StrNCmp = EmitStrNCmp(CI->getArgOperand(0), CI->getArgOperand(1),
StrLen, B, TD, TLI);
if (!StrNCmp)
return 0;
for (Value::use_iterator UI = CI->use_begin(), UE = CI->use_end();
UI != UE; ) {
ICmpInst *Old = cast<ICmpInst>(*UI++);
Value *Cmp = B.CreateICmp(Old->getPredicate(), StrNCmp,
ConstantInt::getNullValue(StrNCmp->getType()),
"cmp");
LCS->replaceAllUsesWith(Old, Cmp);
}
return CI;
}
// See if either input string is a constant string.
StringRef SearchStr, ToFindStr;
bool HasStr1 = getConstantStringInfo(CI->getArgOperand(0), SearchStr);
bool HasStr2 = getConstantStringInfo(CI->getArgOperand(1), ToFindStr);
// fold strstr(x, "") -> x.
if (HasStr2 && ToFindStr.empty())
return B.CreateBitCast(CI->getArgOperand(0), CI->getType());
// If both strings are known, constant fold it.
if (HasStr1 && HasStr2) {
std::string::size_type Offset = SearchStr.find(ToFindStr);
if (Offset == StringRef::npos) // strstr("foo", "bar") -> null
return Constant::getNullValue(CI->getType());
// strstr("abcd", "bc") -> gep((char*)"abcd", 1)
Value *Result = CastToCStr(CI->getArgOperand(0), B);
Result = B.CreateConstInBoundsGEP1_64(Result, Offset, "strstr");
return B.CreateBitCast(Result, CI->getType());
}
// fold strstr(x, "y") -> strchr(x, 'y').
if (HasStr2 && ToFindStr.size() == 1) {
Value *StrChr= EmitStrChr(CI->getArgOperand(0), ToFindStr[0], B, TD, TLI);
return StrChr ? B.CreateBitCast(StrChr, CI->getType()) : 0;
}
return 0;
}
};
} // End anonymous namespace.
namespace llvm {
@ -869,6 +947,7 @@ class LibCallSimplifierImpl {
StrToOpt StrTo;
StrSpnOpt StrSpn;
StrCSpnOpt StrCSpn;
StrStrOpt StrStr;
void initOptimizations();
void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
@ -914,6 +993,7 @@ void LibCallSimplifierImpl::initOptimizations() {
addOpt(LibFunc::strtoull, &StrTo);
addOpt(LibFunc::strspn, &StrSpn);
addOpt(LibFunc::strcspn, &StrCSpn);
addOpt(LibFunc::strstr, &StrStr);
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {