diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -1771,21 +1771,25 @@
 }
 
 bool X86_32ABIInfo::shouldPrimitiveUseInReg(QualType Ty, CCState &State) const {
-  if (!updateFreeRegs(Ty, State))
+  auto CanUseInReg = [this](QualType Ty, CCState &State) {
+    if (State.CC == llvm::CallingConv::X86_FastCall ||
+        State.CC == llvm::CallingConv::X86_VectorCall ||
+        State.CC == llvm::CallingConv::X86_RegCall) {
+      if (getContext().getTypeSize(Ty) > 32)
+        return false;
+
+      return (Ty->isIntegralOrEnumerationType() || Ty->isPointerType() ||
+              Ty->isReferenceType());
+    }
+    return true;
+  };
+
+  if (!CanUseInReg(Ty, State) || !updateFreeRegs(Ty, State))
     return false;
 
   if (IsMCUABI)
     return false;
 
-  if (State.CC == llvm::CallingConv::X86_FastCall ||
-      State.CC == llvm::CallingConv::X86_VectorCall ||
-      State.CC == llvm::CallingConv::X86_RegCall) {
-    if (getContext().getTypeSize(Ty) > 32)
-      return false;
-
-    return (Ty->isIntegralOrEnumerationType() || Ty->isPointerType() ||
-        Ty->isReferenceType());
-  }
 
   return true;
 }
diff --git a/clang/test/CodeGen/mangle-windows.c b/clang/test/CodeGen/mangle-windows.c
--- a/clang/test/CodeGen/mangle-windows.c
+++ b/clang/test/CodeGen/mangle-windows.c
@@ -47,7 +47,7 @@
 // X64: define dso_local void @f8(
 
 void __fastcall f9(long long a, char b, char c, short d) {}
-// CHECK: define dso_local x86_fastcallcc void @"\01@f9@20"(i64 noundef %a, i8 noundef signext %b, i8 noundef signext %c, i16 noundef signext %d)
+// CHECK: define dso_local x86_fastcallcc void @"\01@f9@20"(i64 noundef %a, i8 inreg noundef signext %b, i8 inreg noundef signext %c, i16 noundef signext %d)
 // X64: define dso_local void @f9(
 
 void f12(void) {}