return ConstantInt::get(CI->getType(), 0);
// If this is writing one byte, turn it into fputc.
- if (Bytes == 1) { // fwrite(S,1,1,F) -> fputc(S[0],F)
+ // 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");
EmitFPutC(Char, CI->getArgOperand(3), B, TD);
return ConstantInt::get(CI->getType(), 1);
--- /dev/null
+; RUN: opt < %s -simplify-libcalls -S | FileCheck %s
+
+%FILE = type { i32 }
+
+@.str = private unnamed_addr constant [1 x i8] zeroinitializer, align 1
+
+define i64 @foo(%FILE* %f) {
+; CHECK: %retval = call i64 @fwrite
+ %retval = call i64 @fwrite(i8* getelementptr inbounds ([1 x i8]* @.str, i64 0, i64 0), i64 1, i64 1, %FILE* %f)
+ ret i64 %retval
+}
+
+declare i64 @fwrite(i8*, i64, i64, %FILE *)