instcombine: Migrate strstr optimizations
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
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index e3e9266..b5ea46d 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -86,6 +86,20 @@
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 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 @@
StrToOpt StrTo;
StrSpnOpt StrSpn;
StrCSpnOpt StrCSpn;
+ StrStrOpt StrStr;
void initOptimizations();
void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
@@ -914,6 +993,7 @@
addOpt(LibFunc::strtoull, &StrTo);
addOpt(LibFunc::strspn, &StrSpn);
addOpt(LibFunc::strcspn, &StrCSpn);
+ addOpt(LibFunc::strstr, &StrStr);
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {