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.
---
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 629dfdde33c..f38fe6da8e4 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")
--
2.39.5
