Re: [PATCH] xtensa: Defer storing integer constants into litpool until reload
On Fri, Jun 17, 2022 at 6:48 AM Takayuki 'January June' Suwa
wrote:
>
> Storing integer constants into litpool in the early stage of compilation
> hinders some integer optimizations. In fact, such integer constants are
> not subject to the constant folding process.
>
> For example:
>
> extern unsigned int value;
> extern void foo(void);
> void test(void) {
> if (value == 30001)
> foo();
> }
>
> .literal_position
> .literal .LC0, value
> .literal .LC1, 30001
> test:
> l32ra3, .LC0
> l32ra2, .LC1
> l16ui a3, a3, 0
> extui a2, a2, 0, 16 // runtime zero-extension despite constant
> bne a3, a2, .L1
> j.l foo, a9
> .L1:
> ret.n
>
> This patch defers the placement of integer constants into litpool until
> the start of reload:
>
> .literal_position
> .literal .LC0, value
> .literal .LC1, 30001
> test:
> l32ra3, .LC0
> l32ra2, .LC1
> l16ui a3, a3, 0
> bne a3, a2, .L1
> j.l foo, a9
> .L1:
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/constraints.md (Y):
> Change to include integer constants until reload begins.
> * config/xtensa/predicates.md (move_operand): Ditto.
> * config/xtensa/xtensa.cc (xtensa_emit_move_sequence):
> Change to allow storing integer constants into litpool only after
> reload begins.
> ---
> gcc/config/xtensa/constraints.md | 6 --
> gcc/config/xtensa/predicates.md | 5 +++--
> gcc/config/xtensa/xtensa.cc | 3 ++-
> 3 files changed, 9 insertions(+), 5 deletions(-)
Regtested for target=xtensa-linux-uclibc, no new regressions.
Folded in the description correction and committed to master.
--
Thanks.
-- Max
Re: [PATCH] xtensa: Defer storing integer constants into litpool until reload
erratum:
- extern unsigned int value;
+ extern unsigned short value;
On 2022/06/17 22:47, Takayuki 'January June' Suwa via Gcc-patches wrote:
> Storing integer constants into litpool in the early stage of compilation
> hinders some integer optimizations. In fact, such integer constants are
> not subject to the constant folding process.
>
> For example:
>
> extern unsigned int value;
> extern void foo(void);
> void test(void) {
> if (value == 30001)
> foo();
> }
>
> .literal_position
> .literal .LC0, value
> .literal .LC1, 30001
> test:
> l32ra3, .LC0
> l32ra2, .LC1
> l16ui a3, a3, 0
> extui a2, a2, 0, 16 // runtime zero-extension despite constant
> bne a3, a2, .L1
> j.l foo, a9
> .L1:
> ret.n
>
> This patch defers the placement of integer constants into litpool until
> the start of reload:
>
> .literal_position
> .literal .LC0, value
> .literal .LC1, 30001
> test:
> l32ra3, .LC0
> l32ra2, .LC1
> l16ui a3, a3, 0
> bne a3, a2, .L1
> j.l foo, a9
> .L1:
> ret.n
>
> gcc/ChangeLog:
>
> * config/xtensa/constraints.md (Y):
> Change to include integer constants until reload begins.
> * config/xtensa/predicates.md (move_operand): Ditto.
> * config/xtensa/xtensa.cc (xtensa_emit_move_sequence):
> Change to allow storing integer constants into litpool only after
> reload begins.
[PATCH] xtensa: Defer storing integer constants into litpool until reload
Storing integer constants into litpool in the early stage of compilation
hinders some integer optimizations. In fact, such integer constants are
not subject to the constant folding process.
For example:
extern unsigned int value;
extern void foo(void);
void test(void) {
if (value == 30001)
foo();
}
.literal_position
.literal .LC0, value
.literal .LC1, 30001
test:
l32ra3, .LC0
l32ra2, .LC1
l16ui a3, a3, 0
extui a2, a2, 0, 16 // runtime zero-extension despite constant
bne a3, a2, .L1
j.l foo, a9
.L1:
ret.n
This patch defers the placement of integer constants into litpool until
the start of reload:
.literal_position
.literal .LC0, value
.literal .LC1, 30001
test:
l32ra3, .LC0
l32ra2, .LC1
l16ui a3, a3, 0
bne a3, a2, .L1
j.l foo, a9
.L1:
ret.n
gcc/ChangeLog:
* config/xtensa/constraints.md (Y):
Change to include integer constants until reload begins.
* config/xtensa/predicates.md (move_operand): Ditto.
* config/xtensa/xtensa.cc (xtensa_emit_move_sequence):
Change to allow storing integer constants into litpool only after
reload begins.
---
gcc/config/xtensa/constraints.md | 6 --
gcc/config/xtensa/predicates.md | 5 +++--
gcc/config/xtensa/xtensa.cc | 3 ++-
3 files changed, 9 insertions(+), 5 deletions(-)
diff --git a/gcc/config/xtensa/constraints.md b/gcc/config/xtensa/constraints.md
index e7ac8dbfebf..0b7dcd1440e 100644
--- a/gcc/config/xtensa/constraints.md
+++ b/gcc/config/xtensa/constraints.md
@@ -113,8 +113,10 @@
(define_constraint "Y"
"A constant that can be used in relaxed MOVI instructions."
- (and (match_code "const_int,const_double,const,symbol_ref,label_ref")
- (match_test "TARGET_AUTO_LITPOOLS")))
+ (ior (and (match_code "const_int,const_double,const,symbol_ref,label_ref")
+ (match_test "TARGET_AUTO_LITPOOLS"))
+ (and (match_code "const_int")
+ (match_test "can_create_pseudo_p ()"
;; Memory constraints. Do not use define_memory_constraint here. Doing so
;; causes reload to force some constants into the constant pool, but since
diff --git a/gcc/config/xtensa/predicates.md b/gcc/config/xtensa/predicates.md
index edd13ae41b9..0590c0f81a9 100644
--- a/gcc/config/xtensa/predicates.md
+++ b/gcc/config/xtensa/predicates.md
@@ -147,8 +147,9 @@
(match_test "!constantpool_mem_p (op)
|| GET_MODE_SIZE (mode) % UNITS_PER_WORD == 0")))
(ior (and (match_code "const_int")
- (match_test "GET_MODE_CLASS (mode) == MODE_INT
- && xtensa_simm12b (INTVAL (op))"))
+ (match_test "(GET_MODE_CLASS (mode) == MODE_INT
+&& xtensa_simm12b (INTVAL (op)))
+ || can_create_pseudo_p ()"))
(and (match_code "const_int,const_double,const,symbol_ref,label_ref")
(match_test "(TARGET_CONST16 || TARGET_AUTO_LITPOOLS)
&& CONSTANT_P (op)
diff --git a/gcc/config/xtensa/xtensa.cc b/gcc/config/xtensa/xtensa.cc
index d6f08b11648..c5d00acdf2c 100644
--- a/gcc/config/xtensa/xtensa.cc
+++ b/gcc/config/xtensa/xtensa.cc
@@ -1182,7 +1182,8 @@ xtensa_emit_move_sequence (rtx *operands, machine_mode
mode)
return 1;
}
- if (! TARGET_AUTO_LITPOOLS && ! TARGET_CONST16)
+ if (! TARGET_AUTO_LITPOOLS && ! TARGET_CONST16
+ && ! (CONST_INT_P (src) && can_create_pseudo_p ()))
{
src = force_const_mem (SImode, src);
operands[1] = src;
--
2.20.1
