在 2023/12/29 上午12:11, Xi Ruoyao 写道:
The problem with peephole2 is it uses a naive sliding-window algorithm
and misses many cases. For example:
float a[10000];
float t() { return a[0] + a[8000]; }
is compiled to:
la.local $r13,a
la.local $r12,a+32768
fld.s $f1,$r13,0
fld.s $f0,$r12,-768
fadd.s $f0,$f1,$f0
by trunk. But as we've explained in r14-4851, the following would be
better with -mexplicit-relocs=auto:
pcalau12i $r13,%pc_hi20(a)
pcalau12i $r12,%pc_hi20(a+32000)
fld.s $f1,$r13,%pc_lo12(a)
fld.s $f0,$r12,%pc_lo12(a+32000)
fadd.s $f0,$f1,$f0
However the sliding-window algorithm just won't detect the pcalau12i/fld
pair to be optimized. Use a define_insn_and_split in combine pass will
work around the issue.
gcc/ChangeLog:
* config/loongarch/predicates.md
(symbolic_pcrel_offset_operand): New define_predicate.
(mem_simple_ldst_operand): Likewise.
* config/loongarch/loongarch-protos.h
(loongarch_rewrite_mem_for_simple_ldst): Declare.
* config/loongarch/loongarch.cc
(loongarch_rewrite_mem_for_simple_ldst): Implement.
* config/loongarch/loongarch.md (simple_load<mode>): New
define_insn_and_rewrite.
(simple_load_<su>ext<SUBDI:mode><GPR:mode>): Likewise.
(simple_store<mode>): Likewise.
(define_peephole2): Remove la.local/[f]ld peepholes.
gcc/testsuite/ChangeLog:
* gcc.target/loongarch/explicit-relocs-auto-single-load-store-2.c:
New test.
* gcc.target/loongarch/explicit-relocs-auto-single-load-store-3.c:
New test.
---
Changes from [v2]:
- Match (mem (symbol_ref ...)) instead of (symbol_ref ...) to retain the
attributes of the MEM.
- Add a test to make sure the attributes of the MEM is retained.
[v2]:https://gcc.gnu.org/pipermail/gcc-patches/2023-December/641430.html
Bootstrapped & regtestd on loongarch64-linux-gnu. Ok for trunk?
gcc/config/loongarch/loongarch-protos.h | 1 +
gcc/config/loongarch/loongarch.cc | 16 +++
gcc/config/loongarch/loongarch.md | 114 +++++-------------
gcc/config/loongarch/predicates.md | 13 ++
...explicit-relocs-auto-single-load-store-2.c | 11 ++
...explicit-relocs-auto-single-load-store-3.c | 18 +++
6 files changed, 86 insertions(+), 87 deletions(-)
create mode 100644
gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-2.c
create mode 100644
gcc/testsuite/gcc.target/loongarch/explicit-relocs-auto-single-load-store-3.c
diff --git a/gcc/config/loongarch/loongarch-protos.h
b/gcc/config/loongarch/loongarch-protos.h
/* snip */
diff --git a/gcc/config/loongarch/loongarch.md b/gcc/config/loongarch/loongarch.md
/* snip */
+(define_insn_and_rewrite "simple_load<mode>"
+ [(set (match_operand:LD_AT_LEAST_32_BIT 0 "register_operand" "=r,f")
+ (match_operand:LD_AT_LEAST_32_BIT 1 "mem_simple_ldst_operand" ""))]
+ "loongarch_pre_reload_split () \
+ && la_opt_explicit_relocs == EXPLICIT_RELOCS_AUTO \
Is the '\' here dispensable? I don't seem to have added it when I wrote
the conditions.
+ && (TARGET_CMODEL_NORMAL || TARGET_CMODEL_MEDIUM)"
+ "#"
+ "&& true"
{
- emit_insn (gen_pcalau12i_gr<P:mode> (operands[0], operands[1]));
+ operands[1] = loongarch_rewrite_mem_for_simple_ldst (operands[1]);
})
/* snip */
;; Synchronization instructions.
diff --git a/gcc/config/loongarch/predicates.md
b/gcc/config/loongarch/predicates.md
index 83fea08315c..2158fe7538c 100644
--- a/gcc/config/loongarch/predicates.md
+++ b/gcc/config/loongarch/predicates.md
@@ -579,6 +579,19 @@ (define_predicate "symbolic_pcrel_operand"
return loongarch_symbolic_constant_p (op, &type) && type == SYMBOL_PCREL;
})
+(define_predicate "symbolic_pcrel_offset_operand"
+ (and (match_code "plus")
+ (match_operand 0 "symbolic_pcrel_operand")
+ (match_operand 1 "const_int_operand")))
+
+(define_predicate "mem_simple_ldst_operand"
+ (match_code "mem")
+{
+ op = XEXP (op, 0);
+ return symbolic_pcrel_operand (op, Pmode) ||
+ symbolic_pcrel_offset_operand (op, Pmode);
+})
+
Symbol '||' It shouldn't be at the end of the line.
+ return symbolic_pcrel_operand (op, Pmode)
+ || symbolic_pcrel_offset_operand (op, Pmode);
Others LGTM.
Thanks!
/* snip */
