target/104327: Allow more inlining between different optimization levels.

avr-common.cc introduces the following options that are set depending
on optimization level: -mgas-isr-prologues, -mmain-is-OS-task and
-fsplit-wide-types-early.  The inliner thinks that different options
disallow cross-optimization inlining, so provide can_inline_p.

gcc/
	PR target/104327
	* config/avr/avr.cc (avr_can_inline_p): New static function.
	(TARGET_CAN_INLINE_P): Define to that function.

gcc/config/avr/avr.cc

@@ -1019,6 +1019,19 @@ avr_no_gccisr_function_p (tree func)
   return avr_lookup_function_attribute1 (func, "no_gccisr");
 }
 
+
+/* Implement `TARGET_CAN_INLINE_P'.  */
+/* Some options like -mgas_isr_prologues depend on optimization level,
+   and the inliner might think that due to different options, inlining
+   is not permitted; see PR104327.  */
+
+static bool
+avr_can_inline_p (tree /* caller */, tree /* callee */)
+{
+  // No restrictions whatsoever.
+  return true;
+}
+
 /* Implement `TARGET_SET_CURRENT_FUNCTION'.  */
 /* Sanity cheching for above function attributes.  */
 
@@ -14768,6 +14781,9 @@ avr_float_lib_compare_returns_bool (machine_mode mode, enum rtx_code)
 #undef  TARGET_MD_ASM_ADJUST
 #define TARGET_MD_ASM_ADJUST avr_md_asm_adjust
 
+#undef  TARGET_CAN_INLINE_P
+#define TARGET_CAN_INLINE_P avr_can_inline_p
+
 struct gcc_target targetm = TARGET_INITIALIZER;