From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
To: 70474@debbugs.gnu.org
Subject: bug#70474: [PATCH 2/2] Replace aarch64 CAS and atomic-swap generated JIT code with CASAL and SWPAL instructions
Date: Fri, 19 Apr 2024 22:48:53 +0200 [thread overview]
Message-ID: <6cacb4fa-4547-469b-b28c-c621e664e8be@leastfixedpoint.com> (raw)
In-Reply-To: <825897f1-19fa-4f6a-b459-8db93791d1c3@leastfixedpoint.com>
This appears to make the problem go away. I'm new at working with
`lightening` so I'm not confident I've covered everything that needs
covering, particularly wrt the implementation of cas_atomic. But perhaps
this can be a foundation for someone who knows more than I do to work from.
---
libguile/lightening/lightening/aarch64-cpu.c | 41 ++++++--------------
1 file changed, 11 insertions(+), 30 deletions(-)
diff --git a/libguile/lightening/lightening/aarch64-cpu.c
b/libguile/lightening/lightening/aarch64-cpu.c
index 13aa351e9..30766652f 100644
--- a/libguile/lightening/lightening/aarch64-cpu.c
+++ b/libguile/lightening/lightening/aarch64-cpu.c
@@ -223,8 +223,8 @@ oxxrs(jit_state_t *_jit, int32_t Op,
#define A64_UMULH 0x9bc07c00
#define A64_LDAR 0xc8dffc00
#define A64_STLR 0xc89ffc00
-#define A64_LDAXR 0xc85ffc00
-#define A64_STLXR 0xc800fc00
+#define A64_SWPAL 0xf8e08000
+#define A64_CASAL 0xc8e0fc00
#define A64_STRBI 0x39000000
#define A64_LDRBI 0x39400000
#define A64_LDRSBI 0x39800000
@@ -664,15 +664,15 @@ STLR(jit_state_t *_jit, int32_t Rt, int32_t Rn)
}
static void
-LDAXR(jit_state_t *_jit, int32_t Rt, int32_t Rn) +SWPAL(jit_state_t
*_jit, int32_t Rt, int32_t Rn, int32_t Rs)
{
- return o_xx(_jit, A64_LDAXR, Rt, Rn);
+ return oxxx(_jit, A64_SWPAL, Rt, Rn, Rs);
}
static void
-STLXR(jit_state_t *_jit, int32_t Rt, int32_t Rn, int32_t Rm)
+CASAL(jit_state_t *_jit, int32_t Rt, int32_t Rn, int32_t Rs)
{
- return oxxx(_jit, A64_STLXR, Rt, Rn, Rm);
+ return oxxx(_jit, A64_CASAL, Rt, Rn, Rs);
}
static void
@@ -2532,36 +2532,17 @@ str_atomic(jit_state_t *_jit, int32_t loc,
int32_t val)
static void
swap_atomic(jit_state_t *_jit, int32_t dst, int32_t loc, int32_t val)
{
- void *retry = jit_address(_jit);
- int32_t result = jit_gpr_regno(get_temp_gpr(_jit));
- int32_t val_or_tmp = dst == val ? jit_gpr_regno(get_temp_gpr(_jit)) :
val;
- movr(_jit, val_or_tmp, val);
- LDAXR(_jit, dst, loc);
- STLXR(_jit, val_or_tmp, loc, result);
- jit_patch_there(_jit, bnei(_jit, result, 0), retry);
- if (dst == val) unget_temp_gpr(_jit);
- unget_temp_gpr(_jit);
+ SWPAL(_jit, dst, loc, val);
}
static void
cas_atomic(jit_state_t *_jit, int32_t dst, int32_t loc, int32_t expected,
int32_t desired)
{
- int32_t dst_or_tmp;
- if (dst == loc || dst == expected || dst == expected)
- dst_or_tmp = jit_gpr_regno(get_temp_gpr(_jit));
- else
- dst_or_tmp = dst;
- void *retry = jit_address(_jit);
- LDAXR(_jit, dst_or_tmp, loc);
- jit_reloc_t bad = bner(_jit, dst_or_tmp, expected);
- int result = jit_gpr_regno(get_temp_gpr(_jit));
- STLXR(_jit, desired, loc, result);
- jit_patch_there(_jit, bnei(_jit, result, 0), retry);
- unget_temp_gpr(_jit);
- jit_patch_here(_jit, bad);
- movr(_jit, dst, dst_or_tmp);
- unget_temp_gpr(_jit);
+ if (dst != expected) {
+ movr(_jit, dst, expected);
+ }
+ CASAL(_jit, desired, loc, dst);
}
static void
--
2.44.0
next prev parent reply other threads:[~2024-04-19 20:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-19 10:54 bug#70474: Possible bug with `atomic-box-swap!` on OSX/M3 (?!?!) Tony Garnock-Jones
2024-04-19 12:14 ` bug#70474: Also manifests on an M1 running 14.1.1 and with newer Guile versions Tony Garnock-Jones
2024-04-19 13:19 ` bug#70474: Possible bug with `atomic-box-swap!` on OSX/M3 (?!?!) Christopher Baines
2024-04-19 20:46 ` bug#70474: [PATCH 1/2] Including the cast makes Apple clang 15.0.0 happy; without it, clang is sad Tony Garnock-Jones
2024-04-19 20:48 ` Tony Garnock-Jones [this message]
2024-04-22 7:52 ` bug#70474: Just adding DMB doesn't help Tony Garnock-Jones
2024-04-22 8:18 ` bug#70474: [PATCH] Move the spin loop target to the LDAXR instruction Tony Garnock-Jones
2024-04-22 11:23 ` Tony Garnock-Jones
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