https://gcc.gnu.org/g:6190513486ff39f79a614bb3cd42d94b9c17714a
commit r16-3319-g6190513486ff39f79a614bb3cd42d94b9c17714a
Author: Takayuki 'January June' Suwa <jjsuwa_sys3...@yahoo.co.jp>
Date: Wed Aug 20 20:30:05 2025 +0900
xtensa: Small improvement to "*btrue_INT_MIN"
This patch changes the implementation of the insn to test whether the
result itself is negative or not, rather than the MSB of the result of
the ABS machine instruction. This eliminates the need to consider bit-
endianness and allows for longer branch distances.
/* example */
extern void foo(int);
void test0(int a) {
if (a == -2147483648)
foo(a);
}
void test1(int a) {
if (a != -2147483648)
foo(a);
}
;; before (endianness: little)
test0:
entry sp, 32
abs a8, a2
bbci a8, 31, .L1
mov.n a10, a2
call8 foo
.L1:
retw.n
test1:
entry sp, 32
abs a8, a2
bbsi a8, 31, .L4
mov.n a10, a2
call8 foo
.L4:
retw.n
;; after (endianness-independent)
test0:
entry sp, 32
abs a8, a2
bgez a8, .L1
mov.n a10, a2
call8 foo
.L1:
retw.n
test1:
entry sp, 32
abs a8, a2
bltz a8, .L4
mov.n a10, a2
call8 foo
.L4:
retw.n
gcc/ChangeLog:
* config/xtensa/xtensa.md (*btrue_INT_MIN):
Change the branch insn condition to test for a negative number
rather than testing for the MSB.
Diff:
---
gcc/config/xtensa/xtensa.md | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)
diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 629dfdde33cb..f38fe6da8e48 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -2024,26 +2024,23 @@
[(match_operand:SI 0 "register_operand" "r")
(const_int -2147483648)])
(label_ref (match_operand 1 ""))
- (pc)))]
+ (pc)))
+ (clobber (match_scratch:SI 3 "=a"))]
"TARGET_ABS"
"#"
- "&& can_create_pseudo_p ()"
+ "&& 1"
[(set (match_dup 3)
(abs:SI (match_dup 0)))
(set (pc)
(if_then_else (match_op_dup 2
- [(zero_extract:SI (match_dup 3)
- (const_int 1)
- (match_dup 4))
+ [(match_dup 3)
(const_int 0)])
(label_ref (match_dup 1))
(pc)))]
{
- operands[3] = gen_reg_rtx (SImode);
- operands[4] = GEN_INT (BITS_BIG_ENDIAN ? 0 : 31);
- operands[2] = gen_rtx_fmt_ee (reverse_condition (GET_CODE (operands[2])),
- VOIDmode, XEXP (operands[2], 0),
- const0_rtx);
+ if (GET_CODE (operands[3]) == SCRATCH)
+ operands[3] = gen_reg_rtx (SImode);
+ PUT_CODE (operands[2], GET_CODE (operands[2]) == EQ ? LT : GE);
}
[(set_attr "type" "jump")
(set_attr "mode" "none")
