[patch,avr] Fix PR60300: Minor prologue improvement.

[patch,avr] Fix PR60300: Minor prologue improvement.

[Georg-Johann Lay]

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This patch is a minor improvement of prologue length.  It now allows 
frame sizes of up to 11 to be allocated by RCALL + PUSH 0 sequences but 
limits the number of RCALLs to 3.

The PR has some discussion on size vs. speed consideration w.r. to using 
RCALL in prologues, and following that I picked the rather arbitrary 
upper bound of 3 RCALLs.  The prior maximal frame size opt to such 
sequences was 6 which also never produced more than 3 RCALLs.

Ok for trunk?


Johann

gcc/
	PR target/60300
	* config/avr/constraints.md (Csp): Widen range to [-11..6].
	* config/avr/avr.c (avr_prologue_setup_frame): Limit number
	of RCALLs in prologue to 3.

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Index: config/avr/avr.c
===================================================================
--- config/avr/avr.c	(revision 242672)
+++ config/avr/avr.c	(working copy)
@@ -1687,7 +1687,11 @@ avr_prologue_setup_frame (HOST_WIDE_INT
           /* Stack adjustment by means of RCALL . and/or PUSH __TMP_REG__
              can only handle specific offsets.  */
 
-          if (avr_sp_immediate_operand (gen_int_mode (-size, HImode), HImode))
+          int n_rcall = size / (AVR_3_BYTE_PC ? 3 : 2);
+
+          if (avr_sp_immediate_operand (gen_int_mode (-size, HImode), HImode)
+              // Don't use more than 3 RCALLs.
+              && n_rcall <= 3)
             {
               rtx_insn *sp_plus_insns;
 
Index: config/avr/constraints.md
===================================================================
--- config/avr/constraints.md	(revision 242671)
+++ config/avr/constraints.md	(working copy)
@@ -189,9 +189,9 @@ (define_constraint "Cx4"
        (match_test "avr_popcount_each_byte (op, 4, (1<<0) | (1<<8))")))
 
 (define_constraint "Csp"
-  "Integer constant in the range -6 @dots{} 6."
+  "Integer constant in the range -11 @dots{} 6."
   (and (match_code "const_int")
-       (match_test "IN_RANGE (ival, -6, 6)")))
+       (match_test "IN_RANGE (ival, -11, 6)")))
 
 (define_constraint "Cxf"
   "32-bit integer constant where at least one nibble is 0xf."

Re: [patch,avr] Fix PR60300: Minor prologue improvement.

[Denis Chertykov]

2016-11-22 15:41 GMT+03:00 Georg-Johann Lay <avr@gjlay.de>:
> This patch is a minor improvement of prologue length.  It now allows frame
> sizes of up to 11 to be allocated by RCALL + PUSH 0 sequences but limits the
> number of RCALLs to 3.
>
> The PR has some discussion on size vs. speed consideration w.r. to using
> RCALL in prologues, and following that I picked the rather arbitrary upper
> bound of 3 RCALLs.  The prior maximal frame size opt to such sequences was 6
> which also never produced more than 3 RCALLs.
>
> Ok for trunk?
>
>
> Johann
>
> gcc/
>         PR target/60300
>         * config/avr/constraints.md (Csp): Widen range to [-11..6].
>         * config/avr/avr.c (avr_prologue_setup_frame): Limit number
>         of RCALLs in prologue to 3.

Approved.