re PR target/36424 (avr-gcc use don't saved registers in ISR with -O3…

re PR target/36424 (avr-gcc use don't saved registers in ISR with -O3 ('-frename-registers' ) optimization)

	PR target/36424
	* config/avr/avr.h (HARD_REGNO_RENAME_OK): Define.
	* config/avr/avr.c (avr_hard_regno_rename_ok): New function. 
	* config/avr/avr-protos.h (avr_hard_regno_rename_ok): New prototype.

From-SVN: r136562

gcc/ChangeLog

+2008-07-08  Anatoly Sokolov  <aesok@post.ru>
+
+	PR target/36424
+	* config/avr/avr.h (HARD_REGNO_RENAME_OK): Define.
+	* config/avr/avr.c (avr_hard_regno_rename_ok): New function. 
+	* config/avr/avr-protos.h (avr_hard_regno_rename_ok): New prototype. 
+
 2008-06-07  Danny Smith  <dannysmith@users.sourceforge.net>
 
 	* config/i386/cygming.h (MAYBE_UWIN_CPP_BUILTINS): Remove.

gcc/config/avr/avr-protos.h

@@ -37,6 +37,7 @@ extern int initial_elimination_offset (int from, int to);
 extern int avr_simple_epilogue (void);
 extern void gas_output_limited_string (FILE *file, const char *str);
 extern void gas_output_ascii (FILE *file, const char *str, size_t length);
+extern int avr_hard_regno_rename_ok (unsigned int, unsigned int);
 
 #ifdef TREE_CODE
 extern void asm_output_external (FILE *file, tree decl, char *name);

gcc/config/avr/avr.c

@@ -5916,6 +5916,23 @@ avr_peep2_scratch_safe (rtx scratch)
   return 1;
 }
 
+/* Return nonzero if register OLD_REG can be renamed to register NEW_REG.  */
+
+int
+avr_hard_regno_rename_ok (unsigned int old_reg ATTRIBUTE_UNUSED,
+			  unsigned int new_reg)
+{
+  /* Interrupt functions can only use registers that have already been
+     saved by the prologue, even if they would normally be
+     call-clobbered.  */
+
+  if ((cfun->machine->is_interrupt || cfun->machine->is_signal)
+      && !df_regs_ever_live_p (new_reg))
+    return 0;
+
+  return 1;
+}
+
 /* Output a branch that tests a single bit of a register (QI, HI or SImode)
    or memory location in the I/O space (QImode only).
 

gcc/config/avr/avr.h

@@ -1026,6 +1026,9 @@ mmcu=*:-mmcu=%*}"
 
 #define OBJECT_FORMAT_ELF
 
+#define HARD_REGNO_RENAME_OK(OLD_REG, NEW_REG) \
+  avr_hard_regno_rename_ok (OLD_REG, NEW_REG)
+
 /* A C structure for machine-specific, per-function data.
    This is added to the cfun structure.  */
 struct machine_function GTY(())