jamvm-1.6.0-opcode-guard.patch (1416B)
- From ca11b53896365c948426974cb90e8f71c70d123b Mon Sep 17 00:00:00 2001
- From: Simon South <simon@simonsouth.net>
- Date: Sun, 31 May 2020 20:36:43 -0400
- Subject: [PATCH] Guard floating-point opcodes with explicit memory barrier
- ---
- src/interp/engine/interp-inlining.h | 11 ++++++++++-
- 1 file changed, 10 insertions(+), 1 deletion(-)
- diff --git a/src/interp/engine/interp-inlining.h b/src/interp/engine/interp-inlining.h
- index 3339b0e..4ee5c5a 100644
- --- jamvm/jamvm/src/interp/engine/interp-inlining.h
- +++ jamvm/jamvm/src/interp/engine/interp-inlining.h
- @@ -78,8 +78,17 @@
- 4.3, we need to insert a label, and ensure its address
- is taken (to stop it being optimised out). However,
- this reduces performance on PowerPC by approx 1 - 2%.
- +
- + With gcc 5 and newer an asm statement with a "memory"
- + clobber argument explicitly sets a memory barrier for the
- + compiler, preventing it from reordering memory accesses
- + in a way that breaks decaching.
- */
- -#if (__GNUC__ == 4) && (__GNUC_MINOR__ >= 3)
- +#if (__GNUC__ > 4)
- +#define DEF_GUARD_TABLE(level) /* none */
- +#define GUARD(opcode, level) __asm__("" ::: "memory");
- +#define GUARD_TBLS /* none */
- +#elif (__GNUC__ == 4) && (__GNUC_MINOR__ >= 3)
- #define DEF_GUARD_TABLE(level) DEF_HANDLER_TABLE(level, GUARD)
- #define GUARD(opcode, level) label(opcode, level, GUARD)
- #define GUARD_TBLS , HNDLR_TBLS(GUARD)
- --
- 2.26.2