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.
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."
