From cdd27ca9438906e8bd9d1942fecd69881ff14418 Mon Sep 17 00:00:00 2001
From: Yotam Barnoy
Date: Wed, 1 Sep 2010 12:41:16 +0000
Subject: COMMON: changed read/write endian function to use __may_alias__
 attribute

This is a better solution for the gcc aliasing problem that happens when aliasing a struct onto something else. What happens is that the compiler assumes no aliasing can happen when -O2 and -O3 are activated, and a call to READ_UINT32() followed by WRITE_UINT32() and another READ_UINT32() will be optimized to return the original read value instead of re-reading.

svn-id: r52480
---
 common/endian.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

(limited to 'common')

diff --git a/common/endian.h b/common/endian.h
index db47ff2d07..32f92fd02c 100644
--- a/common/endian.h
+++ b/common/endian.h
@@ -189,22 +189,22 @@
 #elif defined(__GNUC__) && (__GNUC__ >= 4)
 
 	FORCEINLINE uint16 READ_UINT16(const void *ptr) {
-		struct Unaligned16 { uint16 val; } __attribute__ ((__packed__));
+		struct Unaligned16 { uint16 val; } __attribute__ ((__packed__, __may_alias__));
 		return ((const Unaligned16 *)ptr)->val;
 	}
 
 	FORCEINLINE uint32 READ_UINT32(const void *ptr) {
-		struct Unaligned32 { uint32 val; } __attribute__ ((__packed__));
+		struct Unaligned32 { uint32 val; } __attribute__ ((__packed__, __may_alias__));
 		return ((const Unaligned32 *)ptr)->val;
 	}
 
 	FORCEINLINE void WRITE_UINT16(void *ptr, uint16 value) {
-		struct Unaligned16 { uint16 val; } __attribute__ ((__packed__));
+		struct Unaligned16 { uint16 val; } __attribute__ ((__packed__, __may_alias__));
 		((Unaligned16 *)ptr)->val = value;
 	}
 
 	FORCEINLINE void WRITE_UINT32(void *ptr, uint32 value) {
-		struct Unaligned32 { uint32 val; } __attribute__ ((__packed__));
+		struct Unaligned32 { uint32 val; } __attribute__ ((__packed__, __may_alias__));
 		((Unaligned32 *)ptr)->val = value;
 	}
 
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