From ca11b53896365c948426974cb90e8f71c70d123b Mon Sep 17 00:00:00 2001 From: Simon South Date: Sun, 31 May 2020 20:36:43 -0400 Subject: [PATCH 1/2] 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 --- a/src/interp/engine/interp-inlining.h +++ b/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