instcombine: Migrate fwrite optimizations
This patch migrates the fwrite optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@168892 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Utils/SimplifyLibCalls.cpp b/lib/Transforms/Utils/SimplifyLibCalls.cpp
index 5d217bb..00a5d89 100644
--- a/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1577,6 +1577,39 @@
}
};
+struct FWriteOpt : public LibCallOptimization {
+ virtual Value *callOptimizer(Function *Callee, CallInst *CI, IRBuilder<> &B) {
+ // Require a pointer, an integer, an integer, a pointer, returning integer.
+ FunctionType *FT = Callee->getFunctionType();
+ if (FT->getNumParams() != 4 || !FT->getParamType(0)->isPointerTy() ||
+ !FT->getParamType(1)->isIntegerTy() ||
+ !FT->getParamType(2)->isIntegerTy() ||
+ !FT->getParamType(3)->isPointerTy() ||
+ !FT->getReturnType()->isIntegerTy())
+ return 0;
+
+ // Get the element size and count.
+ ConstantInt *SizeC = dyn_cast<ConstantInt>(CI->getArgOperand(1));
+ ConstantInt *CountC = dyn_cast<ConstantInt>(CI->getArgOperand(2));
+ if (!SizeC || !CountC) return 0;
+ uint64_t Bytes = SizeC->getZExtValue()*CountC->getZExtValue();
+
+ // If this is writing zero records, remove the call (it's a noop).
+ if (Bytes == 0)
+ return ConstantInt::get(CI->getType(), 0);
+
+ // If this is writing one byte, turn it into fputc.
+ // This optimisation is only valid, if the return value is unused.
+ if (Bytes == 1 && CI->use_empty()) { // fwrite(S,1,1,F) -> fputc(S[0],F)
+ Value *Char = B.CreateLoad(CastToCStr(CI->getArgOperand(0), B), "char");
+ Value *NewCI = EmitFPutC(Char, CI->getArgOperand(3), B, TD, TLI);
+ return NewCI ? ConstantInt::get(CI->getType(), 1) : 0;
+ }
+
+ return 0;
+ }
+};
+
} // End anonymous namespace.
namespace llvm {
@@ -1634,6 +1667,7 @@
PrintFOpt PrintF;
SPrintFOpt SPrintF;
FPrintFOpt FPrintF;
+ FWriteOpt FWrite;
void initOptimizations();
void addOpt(LibFunc::Func F, LibCallOptimization* Opt);
@@ -1760,6 +1794,7 @@
addOpt(LibFunc::printf, &PrintF);
addOpt(LibFunc::sprintf, &SPrintF);
addOpt(LibFunc::fprintf, &FPrintF);
+ addOpt(LibFunc::fwrite, &FWrite);
}
Value *LibCallSimplifierImpl::optimizeCall(CallInst *CI) {