Revert the .inline semantics change (#22104)

changelogs/changelog_2_0_0.md

@@ -256,8 +256,6 @@
  declared when they are not available on the backend. Previously it would call
  `doAssert false` at runtime despite the condition being compile-time.
 
-- Pragma `{.inline.}` generates `__forceinline` if `__has_attribute(__forceinline)` for GCC and Clang.
-
 - `strutils.split` and `strutils.rsplit` now forbid an empty separator.
 
 - Relative imports will not resolve to searched paths anymore, e.g. `import ./tables` now reports an error properly.

lib/nimbase.h

@@ -84,29 +84,20 @@ __AVR__
 # define __DECLSPEC_SUPPORTED 1
 #endif
 
-
-/* Calling conventions and inline attributes for the supported C compilers */
-#if defined(__GNUC__) || defined(__clang__) /* GCC and Clang */
-# if __has_attribute(__forceinline)
-# define N_INLINE(rettype, name) __attribute__((__forceinline)) rettype name
-# else
-# define N_INLINE(rettype, name) inline rettype name
-# endif
-#elif defined(_MSC_VER) /* MSVC */
-# if _MSC_VER > 1200
-# define N_INLINE(rettype, name) __forceinline rettype name
-# else
-# define N_INLINE(rettype, name) inline rettype name
-# endif
-#elif defined(__TINYC__) || defined(__BORLANDC__) /* TinyC and BorlandC */
-# define N_INLINE(rettype, name) __inline rettype name
-#elif defined(__AVR__) /* Atmel Advanced Virtual RISC */
+/* calling convention mess ----------------------------------------------- */
+#if defined(__GNUC__) || defined(__TINYC__)
+ /* these should support C99's inline */
 # define N_INLINE(rettype, name) inline rettype name
-#else /* Unsupported C compilers */
-# define N_INLINE(rettype, name) rettype name
+#elif defined(__BORLANDC__) || defined(_MSC_VER)
+/* Borland's compiler is really STRANGE here; note that the __fastcall
+ keyword cannot be before the return type, but __inline cannot be after
+ the return type, so we do not handle this mess in the code generator
+ but rather here. */
+# define N_INLINE(rettype, name) __inline rettype name
+#else /* others are less picky: */
+# define N_INLINE(rettype, name) rettype __inline name
 #endif
 
-
 #define N_INLINE_PTR(rettype, name) rettype (*name)
 
 #if defined(__cplusplus)