https://gcc.gnu.org/g:83340869a21baafc889c05b6b5c632a226c509bc
commit r15-9536-g83340869a21baafc889c05b6b5c632a226c509bc
Author: Keith Packard <kei...@keithp.com>
Date: Wed Apr 16 14:10:18 2025 -0600
[PATCH] rx: avoid adding setpsw for rx_cmpstrn when len is const
pattern using rx_cmpstrn is cmpstrsi for which len is a constant -1,
so we'll be moving the setpsw instructions from rx_cmpstrn to
cmpstrnsi as follows:
1. Adjust the predicate on the length operand from "register_operand"
to "nonmemory_operand". This will allow constants to appear here,
instead of having them already transferred into a register.
2. Check to see if the len value is constant, and then check if it is
actually zero. In that case, short-circuit the rest of the pattern
and set the result register to 0.
3. Emit 'setpsw c' and 'setpsw z' instructions when the len is not a
constant, in case it turns out to be zero at runtime.
4. Remove the two 'setpsw' instructions from rx_cmpstrn.
gcc/
* config/rx/rx.md (cmpstrnsi): Allow constant length. For
static length 0, just store 0 into the output register.
For dynamic zero, set C/Z appropriately.
(rxcmpstrn): No longer set C/Z.
Diff:
---
gcc/config/rx/rx.md | 20 ++++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/gcc/config/rx/rx.md b/gcc/config/rx/rx.md
index edb2c96603f5..a3d966efdcc9 100644
--- a/gcc/config/rx/rx.md
+++ b/gcc/config/rx/rx.md
@@ -2541,10 +2541,17 @@
(unspec_volatile:SI [(match_operand:BLK 1 "memory_operand") ;;
String1
(match_operand:BLK 2 "memory_operand")] ;;
String2
UNSPEC_CMPSTRN))
- (use (match_operand:SI 3 "register_operand")) ;; Max
Length
+ (use (match_operand:SI 3 "nonmemory_operand")) ;; Max
Length
(match_operand:SI 4 "immediate_operand")] ;;
Known Align
"rx_allow_string_insns"
{
+ bool const_len = CONST_INT_P (operands[3]);
+ if (const_len && operands[3] == CONST0_RTX (SImode))
+ {
+ emit_move_insn (operands[0], CONST0_RTX (SImode));
+ DONE;
+ }
+
rtx str1 = gen_rtx_REG (SImode, 1);
rtx str2 = gen_rtx_REG (SImode, 2);
rtx len = gen_rtx_REG (SImode, 3);
@@ -2553,6 +2560,13 @@
emit_move_insn (str2, force_operand (XEXP (operands[2], 0), NULL_RTX));
emit_move_insn (len, operands[3]);
+ /* Set flags in case len is zero */
+ if (!const_len)
+ {
+ emit_insn (gen_setpsw (GEN_INT ('C')));
+ emit_insn (gen_setpsw (GEN_INT ('Z')));
+ }
+
emit_insn (gen_rx_cmpstrn (operands[0], operands[1], operands[2]));
DONE;
}
@@ -2590,9 +2604,7 @@
(clobber (reg:SI 3))
(clobber (reg:CC CC_REG))]
"rx_allow_string_insns"
- "setpsw z ; Set flags in case len is zero
- setpsw c
- scmpu ; Perform the string comparison
+ "scmpu ; Perform the string comparison
mov #-1, %0 ; Set up -1 result (which cannot be created
; by the SC insn)
bnc ?+ ; If Carry is not set skip over
