* config/m68k/m68k.h (HARD_REGNO_RENAME_OK): New macro.

	* config/m68k/m68k.c (m68k_hard regno_rename_ok): Disallow
	renaming of non-live registers in interrupt functions.
	* config/m68k/m68k-protos.h (m68k_hard_regno_rename_ok): Add prototype.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@89441 138bc75d-0d04-0410-961f-82ee72b054a4

3 files changed, 25 insertions, 0 deletions

diff --git a/gcc/config/m68k/m68k-protos.h b/gcc/config/m68k/m68k-protos.h
index 8538b8e0d28..4b66927d239 100644
--- a/gcc/config/m68k/m68k-protos.h
+++ b/gcc/config/m68k/m68k-protos.h
@@ -50,9 +50,11 @@ extern void print_operand_address (FILE *, rtx);
 extern void print_operand (FILE *, rtx, int);
 extern void notice_update_cc (rtx, rtx);
 extern rtx legitimize_pic_address (rtx, enum machine_mode, rtx);
+
 #endif /* RTX_CODE */
 
 extern int flags_in_68881 (void);
 extern bool use_return_insn (void);
 extern void override_options (void);
 extern void init_68881_table (void);
+extern int m68k_hard_regno_rename_ok(unsigned int, unsigned int);
diff --git a/gcc/config/m68k/m68k.c b/gcc/config/m68k/m68k.c
index 7a726930720..18b8fb41501 100644
--- a/gcc/config/m68k/m68k.c
+++ b/gcc/config/m68k/m68k.c
@@ -3428,3 +3428,20 @@ m68k_struct_value_rtx (tree fntype ATTRIBUTE_UNUSED,
 {
   return gen_rtx_REG (Pmode, M68K_STRUCT_VALUE_REGNUM);
 }
+
+/* Return nonzero if register old_reg can be renamed to register new_reg.  */
+int
+m68k_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 (m68k_interrupt_function_p (current_function_decl)
+      && !regs_ever_live[new_reg])
+    return 0;
+
+  return 1;
+}
diff --git a/gcc/config/m68k/m68k.h b/gcc/config/m68k/m68k.h
index 6af7116f78b..a7a36f90d9d 100644
--- a/gcc/config/m68k/m68k.h
+++ b/gcc/config/m68k/m68k.h
@@ -480,6 +480,12 @@ extern int target_flags;
   ((REGNO) >= 16 ? GET_MODE_NUNITS (MODE)	\
    : ((GET_MODE_SIZE (MODE) + UNITS_PER_WORD - 1) / UNITS_PER_WORD))
 
+/* A C expression that is nonzero if hard register NEW_REG can be
+   considered for use as a rename register for OLD_REG register.  */
+
+#define HARD_REGNO_RENAME_OK(OLD_REG, NEW_REG) \
+  m68k_hard_regno_rename_ok (OLD_REG, NEW_REG)
+
 /* On the m68k, the cpu registers can hold any mode but the 68881 registers
    can hold only SFmode or DFmode.  */
 #define HARD_REGNO_MODE_OK(REGNO, MODE) \