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:
l32r a3, .LC0
l32r a2, .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:
l32r a3, .LC0
l32r a2, .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
