[CIR][ABI][NFC] Add missing x86-64 signed int CC lowering tests (#713)

clang/test/CIR/Transforms/Target/x86_64/x86_64-call-conv-lowering-pass.cpp

@@ -34,3 +34,31 @@ unsigned long long ULongLong(unsigned long long l) {
   // CHECK: cir.call @_Z9ULongLongy(%2) : (!u64i) -> !u64i
   return ULongLong(l);
 }
+
+/// Test call conv lowering for trivial signext cases. ///
+
+// CHECK: cir.func @_Z4Chara(%arg0: !s8i {cir.signext} loc({{.+}})) -> (!s8i {cir.signext})
+char Char(signed char c) {
+  // CHECK: cir.call @_Z4Chara(%{{.+}}) : (!s8i) -> !s8i
+  return Char(c);
+}
+// CHECK: cir.func @_Z5Shorts(%arg0: !s16i {cir.signext} loc({{.+}})) -> (!s16i {cir.signext})
+short Short(short s) {
+  // CHECK: cir.call @_Z5Shorts(%{{.+}}) : (!s16i) -> !s16i
+  return Short(s);
+}
+// CHECK: cir.func @_Z3Inti(%arg0: !s32i loc({{.+}})) -> !s32i
+int Int(int i) {
+  // CHECK: cir.call @_Z3Inti(%{{.+}}) : (!s32i) -> !s32i
+  return Int(i);
+}
+// CHECK: cir.func @_Z4Longl(%arg0: !s64i loc({{.+}})) -> !s64i
+long Long(long l) {
+  // CHECK: cir.call @_Z4Longl(%{{.+}}) : (!s64i) -> !s64i
+  return Long(l);
+}
+// CHECK: cir.func @_Z8LongLongx(%arg0: !s64i loc({{.+}})) -> !s64i
+long long LongLong(long long l) {
+  // CHECK: cir.call @_Z8LongLongx(%{{.+}}) : (!s64i) -> !s64i
+  return LongLong(l);
+}