* [committed] i386: Implement .SAT_ADD for unsigned scalar integers [PR112600]
@ 2024-06-08 10:23 Uros Bizjak
2024-06-08 12:09 ` Gerald Pfeifer
0 siblings, 1 reply; 3+ messages in thread
From: Uros Bizjak @ 2024-06-08 10:23 UTC (permalink / raw)
To: gcc-patches
[-- Attachment #1: Type: text/plain, Size: 898 bytes --]
The following testcase:
unsigned
add_sat(unsigned x, unsigned y)
{
unsigned z;
return __builtin_add_overflow(x, y, &z) ? -1u : z;
}
currently compiles (-O2) to:
add_sat:
addl %esi, %edi
jc .L3
movl %edi, %eax
ret
.L3:
orl $-1, %eax
ret
We can expand through usadd{m}3 optab to use carry flag from the addition
and generate branchless code using SBB instruction implementing:
unsigned res = x + y;
res |= -(res < x);
add_sat:
addl %esi, %edi
sbbl %eax, %eax
orl %edi, %eax
ret
PR target/112600
gcc/ChangeLog:
* config/i386/i386.md (usadd<mode>3): New expander.
(x86_mov<mode>cc_0_m1_neg): Use SWI mode iterator.
gcc/testsuite/ChangeLog:
* gcc.target/i386/pr112600-a.c: New test.
Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.
Uros.
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diff --git a/gcc/config/i386/i386.md b/gcc/config/i386/i386.md
index ffcf63e1cba..bc2ef819df6 100644
--- a/gcc/config/i386/i386.md
+++ b/gcc/config/i386/i386.md
@@ -9870,6 +9870,26 @@ (define_insn_and_split "*sub<mode>3_ne_0"
operands[1] = force_reg (<MODE>mode, operands[1]);
})
+(define_expand "usadd<mode>3"
+ [(set (match_operand:SWI 0 "register_operand")
+ (us_plus:SWI (match_operand:SWI 1 "register_operand")
+ (match_operand:SWI 2 "<general_operand>")))]
+ ""
+{
+ rtx res = gen_reg_rtx (<MODE>mode);
+ rtx msk = gen_reg_rtx (<MODE>mode);
+ rtx dst;
+
+ emit_insn (gen_add<mode>3_cc_overflow_1 (res, operands[1], operands[2]));
+ emit_insn (gen_x86_mov<mode>cc_0_m1_neg (msk));
+ dst = expand_simple_binop (<MODE>mode, IOR, res, msk,
+ operands[0], 1, OPTAB_DIRECT);
+
+ if (!rtx_equal_p (dst, operands[0]))
+ emit_move_insn (operands[0], dst);
+ DONE;
+})
+
;; The patterns that match these are at the end of this file.
(define_expand "<insn>xf3"
@@ -24945,8 +24965,8 @@ (define_insn "*x86_mov<mode>cc_0_m1_neg"
(define_expand "x86_mov<mode>cc_0_m1_neg"
[(parallel
- [(set (match_operand:SWI48 0 "register_operand")
- (neg:SWI48 (ltu:SWI48 (reg:CCC FLAGS_REG) (const_int 0))))
+ [(set (match_operand:SWI 0 "register_operand")
+ (neg:SWI (ltu:SWI (reg:CCC FLAGS_REG) (const_int 0))))
(clobber (reg:CC FLAGS_REG))])])
(define_split
diff --git a/gcc/testsuite/gcc.target/i386/pr112600-a.c b/gcc/testsuite/gcc.target/i386/pr112600-a.c
new file mode 100644
index 00000000000..fa122bc7a3f
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr112600-a.c
@@ -0,0 +1,32 @@
+/* PR target/112600 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler-times "sbb" 4 } } */
+
+unsigned char
+add_sat_char (unsigned char x, unsigned char y)
+{
+ unsigned char z;
+ return __builtin_add_overflow(x, y, &z) ? -1u : z;
+}
+
+unsigned short
+add_sat_short (unsigned short x, unsigned short y)
+{
+ unsigned short z;
+ return __builtin_add_overflow(x, y, &z) ? -1u : z;
+}
+
+unsigned int
+add_sat_int (unsigned int x, unsigned int y)
+{
+ unsigned int z;
+ return __builtin_add_overflow(x, y, &z) ? -1u : z;
+}
+
+unsigned long
+add_sat_long (unsigned long x, unsigned long y)
+{
+ unsigned long z;
+ return __builtin_add_overflow(x, y, &z) ? -1ul : z;
+}
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [committed] i386: Implement .SAT_ADD for unsigned scalar integers [PR112600]
2024-06-08 10:23 [committed] i386: Implement .SAT_ADD for unsigned scalar integers [PR112600] Uros Bizjak
@ 2024-06-08 12:09 ` Gerald Pfeifer
2024-06-08 20:50 ` Uros Bizjak
0 siblings, 1 reply; 3+ messages in thread
From: Gerald Pfeifer @ 2024-06-08 12:09 UTC (permalink / raw)
To: Uros Bizjak; +Cc: gcc-patches
On Sat, 8 Jun 2024, Uros Bizjak wrote:
> gcc/ChangeLog:
>
> * config/i386/i386.md (usadd<mode>3): New expander.
> (x86_mov<mode>cc_0_m1_neg): Use SWI mode iterator.
When you write "committed", did you actually push?
If so, us being on Git now it might be good to adjust terminology.
Gerald
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [committed] i386: Implement .SAT_ADD for unsigned scalar integers [PR112600]
2024-06-08 12:09 ` Gerald Pfeifer
@ 2024-06-08 20:50 ` Uros Bizjak
0 siblings, 0 replies; 3+ messages in thread
From: Uros Bizjak @ 2024-06-08 20:50 UTC (permalink / raw)
To: Gerald Pfeifer; +Cc: gcc-patches
On Sat, Jun 8, 2024 at 2:09 PM Gerald Pfeifer <gerald@pfeifer.com> wrote:
>
> On Sat, 8 Jun 2024, Uros Bizjak wrote:
> > gcc/ChangeLog:
> >
> > * config/i386/i386.md (usadd<mode>3): New expander.
> > (x86_mov<mode>cc_0_m1_neg): Use SWI mode iterator.
>
> When you write "committed", did you actually push?
Yes, IIRC, the request was to mark pushed change with the word "committed".
> If so, us being on Git now it might be good to adjust terminology.
No problem, I can say "pushed" if that is more descriptive.
Thanks,
Uros.
^ permalink raw reply [flat|nested] 3+ messages in thread
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2024-06-08 10:23 [committed] i386: Implement .SAT_ADD for unsigned scalar integers [PR112600] Uros Bizjak
2024-06-08 12:09 ` Gerald Pfeifer
2024-06-08 20:50 ` Uros Bizjak
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