The only pattern for which the len may be zero is cmpstrsni. The other
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.
Signed-off-by: Keith Packard <kei...@keithp.com>
---
gcc/config/rx/rx.md | 21 +++++++++++++++++----
1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/gcc/config/rx/rx.md b/gcc/config/rx/rx.md
index edb2c96603f..b3f36379fe2 100644
--- a/gcc/config/rx/rx.md
+++ b/gcc/config/rx/rx.md
@@ -2541,10 +2541,20 @@ (define_expand "cmpstrnsi"
(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)
+ {
+ if (INTVAL(operands[3]) == 0)
+ {
+ emit_move_insn (operands[0], GEN_INT(0));
+ DONE;
+ }
+ }
+
rtx str1 = gen_rtx_REG (SImode, 1);
rtx str2 = gen_rtx_REG (SImode, 2);
rtx len = gen_rtx_REG (SImode, 3);
@@ -2553,6 +2563,11 @@ (define_expand "cmpstrnsi"
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 +2605,7 @@ (define_insn "rx_cmpstrn"
(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
--
2.49.0
