instcombine: Migrate strncpy optimizations
This patch migrates the strncpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167102 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index bc36001..cc03573 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -628,6 +628,53 @@
}
};
+struct StrNCpyOpt : public LibCallOptimization {
+ virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+ FunctionType *FT = Callee->getFunctionType();
+ if (FT->getNumParams() != 3 || FT->getReturnType() != FT->getParamType(0) ||
+ FT->getParamType(0) != FT->getParamType(1) ||
+ FT->getParamType(0) != B.getInt8PtrTy() ||
+ !FT->getParamType(2)->isIntegerTy())
+ return 0;
+
+ Value *Dst = CI->getArgOperand(0);
+ Value *Src = CI->getArgOperand(1);
+ Value *LenOp = CI->getArgOperand(2);
+
+ // See if we can get the length of the input string.
+ uint64_t SrcLen = GetStringLength(Src);
+ if (SrcLen == 0) return 0;
+ --SrcLen;
+
+ if (SrcLen == 0) {
+ // strncpy(x, "", y) -> memset(x, '\0', y, 1)
+ B.CreateMemSet(Dst, B.getInt8('\0'), LenOp, 1);
+ return Dst;
+ }
+
+ uint64_t Len;
+ if (ConstantInt *LengthArg = dyn_cast<ConstantInt>(LenOp))
+ Len = LengthArg->getZExtValue();
+ else
+ return 0;
+
+ if (Len == 0) return Dst; // strncpy(x, y, 0) -> x
+
+ // These optimizations require DataLayout.
+ if (!TD) return 0;
+
+ // Let strncpy handle the zero padding
+ if (Len > SrcLen+1) return 0;
+
+ Type *PT = FT->getParamType(0);
+ // strncpy(x, s, c) -> memcpy(x, s, c, 1) [s and c are constant]
+ B.CreateMemCpy(Dst, Src,
+ ConstantInt::get(TD->getIntPtrType(PT), Len), 1);
+
+ return Dst;
+ }
+};
+
} // End anonymous namespace.
namespace llvm {
@@ -654,6 +701,7 @@
StrNCmpOpt StrNCmp;
StrCpyOpt StrCpy;
StpCpyOpt StpCpy;
+ StrNCpyOpt StrNCpy;
void initOptimizations();
public:
@@ -684,6 +732,7 @@
Optimizations["strncmp"] = &StrNCmp;
Optimizations["strcpy"] = &StrCpy;
Optimizations["stpcpy"] = &StpCpy;
+ Optimizations["strncpy"] = &StrNCpy;
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {