instcombine: Migrate strcat and strncat optimizations
This patch migrates the strcat and strncat optimizations from the
simplify-libcalls pass into the instcombine library call simplifier.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165874 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 7e4c1e7..2c8fb8b 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -222,6 +222,104 @@
}
};
+//===----------------------------------------------------------------------===//
+// String and Memory Library Call Optimizations
+//===----------------------------------------------------------------------===//
+
+struct StrCatOpt : public LibCallOptimization {
+ virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+ // Verify the "strcat" function prototype.
+ FunctionType *FT = Callee->getFunctionType();
+ if (FT->getNumParams() != 2 ||
+ FT->getReturnType() != B.getInt8PtrTy() ||
+ FT->getParamType(0) != FT->getReturnType() ||
+ FT->getParamType(1) != FT->getReturnType())
+ return 0;
+
+ // Extract some information from the instruction
+ Value *Dst = CI->getArgOperand(0);
+ Value *Src = CI->getArgOperand(1);
+
+ // See if we can get the length of the input string.
+ uint64_t Len = GetStringLength(Src);
+ if (Len == 0) return 0;
+ --Len; // Unbias length.
+
+ // Handle the simple, do-nothing case: strcat(x, "") -> x
+ if (Len == 0)
+ return Dst;
+
+ // These optimizations require DataLayout.
+ if (!TD) return 0;
+
+ return emitStrLenMemCpy(Src, Dst, Len, B);
+ }
+
+ Value *emitStrLenMemCpy(Value *Src, Value *Dst, uint64_t Len,
+ IRBuilder<> &B) {
+ // We need to find the end of the destination string. That's where the
+ // memory is to be moved to. We just generate a call to strlen.
+ Value *DstLen = EmitStrLen(Dst, B, TD, TLI);
+ if (!DstLen)
+ return 0;
+
+ // Now that we have the destination's length, we must index into the
+ // destination's pointer to get the actual memcpy destination (end of
+ // the string .. we're concatenating).
+ Value *CpyDst = B.CreateGEP(Dst, DstLen, "endptr");
+
+ // We have enough information to now generate the memcpy call to do the
+ // concatenation for us. Make a memcpy to copy the nul byte with align = 1.
+ B.CreateMemCpy(CpyDst, Src,
+ ConstantInt::get(TD->getIntPtrType(*Context), Len + 1), 1);
+ return Dst;
+ }
+};
+
+struct StrNCatOpt : public StrCatOpt {
+ virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+ // Verify the "strncat" function prototype.
+ FunctionType *FT = Callee->getFunctionType();
+ if (FT->getNumParams() != 3 ||
+ FT->getReturnType() != B.getInt8PtrTy() ||
+ FT->getParamType(0) != FT->getReturnType() ||
+ FT->getParamType(1) != FT->getReturnType() ||
+ !FT->getParamType(2)->isIntegerTy())
+ return 0;
+
+ // Extract some information from the instruction
+ Value *Dst = CI->getArgOperand(0);
+ Value *Src = CI->getArgOperand(1);
+ uint64_t Len;
+
+ // We don't do anything if length is not constant
+ if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(CI->getArgOperand(2)))
+ Len = LengthArg->getZExtValue();
+ else
+ return 0;
+
+ // See if we can get the length of the input string.
+ uint64_t SrcLen = GetStringLength(Src);
+ if (SrcLen == 0) return 0;
+ --SrcLen; // Unbias length.
+
+ // Handle the simple, do-nothing cases:
+ // strncat(x, "", c) -> x
+ // strncat(x, c, 0) -> x
+ if (SrcLen == 0 || Len == 0) return Dst;
+
+ // These optimizations require DataLayout.
+ if (!TD) return 0;
+
+ // We don't optimize this case
+ if (Len < SrcLen) return 0;
+
+ // strncat(x, s, c) -> strcat(x, s)
+ // s is constant so the strcat can be optimized further
+ return emitStrLenMemCpy(Src, Dst, SrcLen, B);
+ }
+};
+
} // End anonymous namespace.
namespace llvm {
@@ -239,6 +337,10 @@
StrCpyChkOpt StrCpyChk;
StrNCpyChkOpt StrNCpyChk;
+ // String and memory library call optimizations.
+ StrCatOpt StrCat;
+ StrNCatOpt StrNCat;
+
void initOptimizations();
public:
LibCallSimplifierImpl(const DataLayout *TD, const TargetLibraryInfo *TLI) {
@@ -258,6 +360,10 @@
Optimizations["__stpcpy_chk"] = &StrCpyChk;
Optimizations["__strncpy_chk"] = &StrNCpyChk;
Optimizations["__stpncpy_chk"] = &StrNCpyChk;
+
+ // String and memory library call optimizations.
+ Optimizations["strcat"] = &StrCat;
+ Optimizations["strncat"] = &StrNCat;
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {