diff --git a/llvm/include/llvm/Transforms/Utils/BuildLibCalls.h b/llvm/include/llvm/Transforms/Utils/BuildLibCalls.h
--- a/llvm/include/llvm/Transforms/Utils/BuildLibCalls.h
+++ b/llvm/include/llvm/Transforms/Utils/BuildLibCalls.h
@@ -226,8 +226,8 @@
   /// Emit a call to the puts function. This assumes that Str is some pointer.
   Value *emitPutS(Value *Str, IRBuilderBase &B, const TargetLibraryInfo *TLI);
 
-  /// Emit a call to the fputc function. This assumes that Char can be casted to
-  /// int (currently assuming int is i32), and File is a pointer to FILE.
+  /// Emit a call to the fputc function. This assumes that Char is an 'int', and
+  /// File is a pointer to FILE.
   Value *emitFPutC(Value *Char, Value *File, IRBuilderBase &B,
                    const TargetLibraryInfo *TLI);
 
diff --git a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
--- a/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/BuildLibCalls.cpp
@@ -1841,8 +1841,6 @@
                                         IntTy, File->getType());
   if (File->getType()->isPointerTy())
     inferNonMandatoryLibFuncAttrs(M, FPutcName, *TLI);
-  Char = B.CreateIntCast(Char, IntTy, /*isSigned*/true,
-                         "chari");
   CallInst *CI = B.CreateCall(F, {Char, File}, FPutcName);
 
   if (const Function *Fn =
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
--- a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -3218,11 +3218,13 @@
 
   // Decode the second character of the format string.
   if (FormatStr[1] == 'c') {
-    // fprintf(F, "%c", chr) --> fputc(chr, F)
+    // fprintf(F, "%c", chr) --> fputc((int)chr, F)
     if (!CI->getArgOperand(2)->getType()->isIntegerTy())
       return nullptr;
-    return copyFlags(
-        *CI, emitFPutC(CI->getArgOperand(2), CI->getArgOperand(0), B, TLI));
+    Type *IntTy = B.getIntNTy(TLI->getIntSize());
+    Value *V = B.CreateIntCast(CI->getArgOperand(2), IntTy, /*isSigned*/ true,
+                               "chari");
+    return copyFlags(*CI, emitFPutC(V, CI->getArgOperand(0), B, TLI));
   }
 
   if (FormatStr[1] == 's') {
@@ -3289,7 +3291,9 @@
     if (Bytes == 1 && CI->use_empty()) { // fwrite(S,1,1,F) -> fputc(S[0],F)
       Value *Char = B.CreateLoad(B.getInt8Ty(),
                                  castToCStr(CI->getArgOperand(0), B), "char");
-      Value *NewCI = emitFPutC(Char, CI->getArgOperand(3), B, TLI);
+      Type *IntTy = B.getIntNTy(TLI->getIntSize());
+      Value *Cast = B.CreateIntCast(Char, IntTy, /*isSigned*/ true, "chari");
+      Value *NewCI = emitFPutC(Cast, CI->getArgOperand(3), B, TLI);
       return NewCI ? ConstantInt::get(CI->getType(), 1) : nullptr;
     }
   }