| 1 | From ca11b53896365c948426974cb90e8f71c70d123b Mon Sep 17 00:00:00 2001
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| 2 | From: Simon South <[email protected]>
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| 3 | Date: Sun, 31 May 2020 20:36:43 -0400
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| 4 | Subject: [PATCH] Guard floating-point opcodes with explicit memory barrier
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| 5 |
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| 6 | ---
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| 7 | src/interp/engine/interp-inlining.h | 11 ++++++++++-
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| 8 | 1 file changed, 10 insertions(+), 1 deletion(-)
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| 9 |
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| 10 | diff --git a/src/interp/engine/interp-inlining.h b/src/interp/engine/interp-inlining.h
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| 11 | index 3339b0e..4ee5c5a 100644
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| 12 | |
| 13 | |
| 14 | @@ -78,8 +78,17 @@
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| 15 | 4.3, we need to insert a label, and ensure its address
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| 16 | is taken (to stop it being optimised out). However,
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| 17 | this reduces performance on PowerPC by approx 1 - 2%.
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| 18 | +
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| 19 | + With gcc 5 and newer an asm statement with a "memory"
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| 20 | + clobber argument explicitly sets a memory barrier for the
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| 21 | + compiler, preventing it from reordering memory accesses
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| 22 | + in a way that breaks decaching.
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| 23 | */
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| 24 | -#if (__GNUC__ == 4) && (__GNUC_MINOR__ >= 3)
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| 25 | +#if (__GNUC__ > 4)
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| 26 | +#define DEF_GUARD_TABLE(level) /* none */
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| 27 | +#define GUARD(opcode, level) __asm__("" ::: "memory");
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| 28 | +#define GUARD_TBLS /* none */
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| 29 | +#elif (__GNUC__ == 4) && (__GNUC_MINOR__ >= 3)
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| 30 | #define DEF_GUARD_TABLE(level) DEF_HANDLER_TABLE(level, GUARD)
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| 31 | #define GUARD(opcode, level) label(opcode, level, GUARD)
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| 32 | #define GUARD_TBLS , HNDLR_TBLS(GUARD)
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| 33 | --
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| 34 | 2.26.2
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| 35 |
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