Message ID | 17c66d91-37c5-7891-5489-955b4dc8a059@yahoo.co.jp |
---|---|
State | New |
Headers | show |
Series | xtensa: Defer storing integer constants into litpool until reload | expand |
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: > 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.
On Fri, Jun 17, 2022 at 6:48 AM Takayuki 'January June' Suwa <jjsuwa_sys3175@yahoo.co.jp> 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: > 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(-) Regtested for target=xtensa-linux-uclibc, no new regressions. Folded in the description correction and committed to master.
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;