Hi DJ,
The patch below makes some changes to the way the RL78 backend handles
the generation of interrupt functions. Specifically it:
* Uses register bank 3 instead of register bank 0 inside the
handler.
* Tweaks the need_to_save() function so only those registers that
will be clobbered by the handler are push onto the stack.
* Provides support for a "naked" function attribute so that
programmers can write their own mixed C/assembler interrupt
handlers if they want to.
Tested, with no regressions, on an rl78-elf target.
OK to apply ?
Cheers
Nick
gcc/ChangeLog
2013-05-01 Nick Clifton <ni...@redhat.com>
* config/rl78/rl78.c (need_to_save): Make into a boolean
function. Do not save register bank 0 registers in interrupt
handlers.
(rl78_attribute_table): Add "naked".
(rl78_is_naked_func): New function.
(rl78_expand_prologue): Skip prologue generation for naked
functions. Switch to register bank 3 for interrupt handlers.
(rl78_expand_epilogue): Skip epilogue generation for naked
functions. Switch back to register bank 0 in interrupt
handlers.
* doc/extend.texi: Document that the RL78 backend supports the
"naked" function attribute.
Index: gcc/config/rl78/rl78.c
===================================================================
--- gcc/config/rl78/rl78.c (revision 198496)
+++ gcc/config/rl78/rl78.c (working copy)
@@ -373,34 +373,42 @@
return true;
}
-/* Returns nonzero if the given register needs to be saved by the
+/* Returns true if the given register needs to be saved by the
current function. */
-static int
-need_to_save (int regno)
+static bool
+need_to_save (unsigned int regno)
{
if (is_interrupt_func (cfun->decl))
{
+ /* We don't need to save registers that have
+ been reserved for interrupt handlers. */
+ if (regno > 23)
+ return false;
+
+ /* If the handler is a non-leaf function then it may call
+ non-interrupt aware routines which will happily clobber
+ any call_used registers, so we have to preserve them. */
+ if (!crtl->is_leaf && call_used_regs[regno])
+ return true;
+
+ /* Interrupt functions do not use register bank 0. */
if (regno < 8)
- return 1; /* don't know what devirt will need */
- if (regno > 23)
- return 0; /* don't need to save interrupt registers */
- if (crtl->is_leaf)
- {
- return df_regs_ever_live_p (regno);
- }
- else
- return 1;
+ return false;
+
+ /* Otherwise we only have to save a register, call_used
+ or not, if it is used by this handler. */
+ return df_regs_ever_live_p (regno);
}
if (regno == FRAME_POINTER_REGNUM && frame_pointer_needed)
- return 1;
+ return true;
if (fixed_regs[regno])
- return 0;
+ return false;
if (crtl->calls_eh_return)
- return 1;
+ return true;
if (df_regs_ever_live_p (regno)
&& !call_used_regs[regno])
- return 1;
- return 0;
+ return true;
+ return false;
}
/* We use this to wrap all emitted insns in the prologue. */
@@ -499,6 +507,8 @@
false },
{ "brk_interrupt", 0, 0, true, false, false, rl78_handle_func_attribute,
false },
+ { "naked", 0, 0, true, false, false, rl78_handle_func_attribute,
+ false },
{ NULL, 0, 0, false, false, false, NULL, false }
};
@@ -825,6 +833,12 @@
return rv;
}
+static int
+rl78_is_naked_func (void)
+{
+ return (lookup_attribute ("naked", DECL_ATTRIBUTES (current_function_decl))
!= NULL_TREE);
+}
+
/* Expand the function prologue (from the prologue pattern). */
void
rl78_expand_prologue (void)
@@ -833,19 +847,22 @@
rtx sp = gen_rtx_REG (HImode, STACK_POINTER_REGNUM);
int rb = 0;
+ if (rl78_is_naked_func ())
+ return;
+
+ rb = is_interrupt_func (cfun->decl) ? -1 : 0;
+
if (!cfun->machine->computed)
rl78_compute_frame_info ();
if (flag_stack_usage_info)
current_function_static_stack_size = cfun->machine->framesize;
- if (is_interrupt_func (cfun->decl))
- emit_insn (gen_sel_rb (GEN_INT (0)));
-
for (i = 0; i < 16; i++)
if (cfun->machine->need_to_push [i])
{
int need_bank = i/4;
+
if (need_bank != rb)
{
emit_insn (gen_sel_rb (GEN_INT (need_bank)));
@@ -853,7 +870,14 @@
}
F (emit_insn (gen_push (gen_rtx_REG (HImode, i*2))));
}
- if (rb != 0)
+
+ /* Interrupt functions use rb3 instead of rb0. */
+ if (is_interrupt_func (cfun->decl))
+ {
+ if (rb != 3)
+ emit_insn (gen_sel_rb (GEN_INT (3)));
+ }
+ else if (rb != 0)
emit_insn (gen_sel_rb (GEN_INT (0)));
if (frame_pointer_needed)
@@ -877,6 +901,11 @@
rtx sp = gen_rtx_REG (HImode, STACK_POINTER_REGNUM);
int rb = 0;
+ if (rl78_is_naked_func ())
+ return;
+
+ rb = is_interrupt_func (cfun->decl) ? 3 : 0;
+
if (frame_pointer_needed)
{
emit_move_insn (gen_rtx_REG (HImode, STACK_POINTER_REGNUM),
Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi (revision 198496)
+++ gcc/doc/extend.texi (working copy)
@@ -3142,7 +3142,7 @@
@item naked
@cindex function without a prologue/epilogue code
-Use this attribute on the ARM, AVR, MCORE, RX and SPU ports to indicate that
+Use this attribute on the ARM, AVR, MCORE, RL78, RX and SPU ports to indicate
that
the specified function does not need prologue/epilogue sequences generated by
the compiler. It is up to the programmer to provide these sequences. The
only statements that can be safely included in naked functions are
