Re: [PATCH 1/2 v2] xtensa: Recover constant synthesis for HImode after LRA transition

[Max Filippov]

On Sun, Feb 4, 2024 at 2:20 AM Takayuki 'January June' Suwa
 wrote:
>
> After LRA transition, HImode constants that don't fit into signed 12 bits
> are no longer subject to constant synthesis:
>
> /* example */
> void test(void) {
>   short foo = 32767;
>   __asm__ ("" :: "r"(foo));
> }
>
> ;; before
> .literal_position
> .literal .LC0, 32767
> test:
> l32ra9, .LC0
> ret.n
>
> This patch fixes that:
>
> ;; after
> test:
> movi.n  a9, -1
> extui   a9, a9, 17, 15
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/xtensa.md (SHI): New mode iterator.
> (2 split patterns related to constsynth):
> Change to also accept HImode operands.
> ---
>  gcc/config/xtensa/xtensa.md | 22 ++
>  1 file changed, 14 insertions(+), 8 deletions(-)

Regtested for target=xtensa-linux-uclibc, no new regressions.
Committed to master.

-- 
Thanks.
-- Max

[PATCH 1/2 v2] xtensa: Recover constant synthesis for HImode after LRA transition

[Takayuki 'January June' Suwa]

After LRA transition, HImode constants that don't fit into signed 12 bits
are no longer subject to constant synthesis:

/* example */
void test(void) {
  short foo = 32767;
  __asm__ ("" :: "r"(foo));
}

;; before
.literal_position
.literal .LC0, 32767
test:
l32ra9, .LC0
ret.n

This patch fixes that:

;; after
test:
movi.n  a9, -1
extui   a9, a9, 17, 15
ret.n

gcc/ChangeLog:

* config/xtensa/xtensa.md (SHI): New mode iterator.
(2 split patterns related to constsynth):
Change to also accept HImode operands.
---
 gcc/config/xtensa/xtensa.md | 22 ++
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/gcc/config/xtensa/xtensa.md b/gcc/config/xtensa/xtensa.md
index 13b8b57f1fc..1a2249b059a 100644
--- a/gcc/config/xtensa/xtensa.md
+++ b/gcc/config/xtensa/xtensa.md
@@ -87,6 +87,10 @@
 ;; the same template.
 (define_mode_iterator HQI [HI QI])
 
+;; This mode iterator allows the SI and HI patterns to be defined from
+;; the same template.
+(define_mode_iterator SHI [SI HI])
+
 
 ;; Attributes.
 
@@ -1291,28 +1295,30 @@
(set_attr "length"  "2,2,2,2,2,2,3,3,3,3,6,3,3,3,3,3")])
 
 (define_split
-  [(set (match_operand:SI 0 "register_operand")
-   (match_operand:SI 1 "const_int_operand"))]
+  [(set (match_operand:SHI 0 "register_operand")
+   (match_operand:SHI 1 "const_int_operand"))]
   "!TARGET_CONST16 && !TARGET_AUTO_LITPOOLS
&& ! xtensa_split1_finished_p ()
&& ! xtensa_simm12b (INTVAL (operands[1]))"
   [(set (match_dup 0)
(match_dup 1))]
 {
-  operands[1] = force_const_mem (SImode, operands[1]);
+  operands[1] = force_const_mem (mode, operands[1]);
 })
 
 (define_split
-  [(set (match_operand:SI 0 "register_operand")
-   (match_operand:SI 1 "constantpool_operand"))]
+  [(set (match_operand:SHI 0 "register_operand")
+   (match_operand:SHI 1 "constantpool_operand"))]
   "! optimize_debug && reload_completed"
   [(const_int 0)]
 {
-  rtx x = avoid_constant_pool_reference (operands[1]);
+  rtx x = avoid_constant_pool_reference (operands[1]), dst = operands[0];
   if (! CONST_INT_P (x))
 FAIL;
-  if (! xtensa_constantsynth (operands[0], INTVAL (x)))
-emit_move_insn (operands[0], x);
+  if (mode == HImode)
+dst = gen_rtx_REG (SImode, REGNO (dst));
+  if (! xtensa_constantsynth (dst, INTVAL (x)))
+emit_move_insn (dst, x);
   DONE;
 })
 
-- 
2.30.2