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Don't use lwsync on E500

GCC generates lwsync instructions for PowerPC (both from and 
hardcoded in libstdc++'s atomicity configuration).

These generate illegal instruction errors on E500 CPUs, which only have an 
msync instruction (same bit-pattern as sync; lwsync involves setting a bit 
that's reserved in msync).  Although Power ISA 2.03 requires lwsync, an 
older Book E only has msync.

This patch makes GCC use plain sync instead of lwsync on E500 (I don't see 
a need for a separate command-line option for this at present).  This 
removes about 2500 FAILs for powerpc-none-linux-gnuspe 
--enable-e500_double.  (For some reason only one of those FAILs appears 
for me in 4.1 testing: that in ia64-sync-1.c, the others only appear in 
4.2 and 4.3 testing.  They don't appear in Edmar's results on 
gcc-testresults because those have kernel emulation enabled in order to 
use a root filesystem with ordinary PowerPC binaries.)

Tested with no regressions with a cross to powerpc-none-linux-gnuspe.  OK 
to commit to mainline, 4.2, 4.1?

2006-11-16  Joseph Myers  <>

	* config/rs6000/rs6000.h (TARGET_NO_LWSYNC): Define.
	* config/rs6000/rs6000-c.c (rs6000_cpu_cpp_builtins): Define
	* config/rs6000/ (lwsync): Emit plain sync if

	* config/cpu/powerpc/atomic_word.h (_GLIBCXX_WRITE_MEM_BARRIER):
	Use plain sync if __NO_LWSYNC__.

Index: gcc/config/rs6000/rs6000-c.c
--- gcc/config/rs6000/rs6000-c.c	(revision 118892)
+++ gcc/config/rs6000/rs6000-c.c	(working copy)
@@ -127,6 +127,9 @@
   /* Used by lwarx/stwcx. errata work-around.  */
   if (rs6000_cpu == PROCESSOR_PPC405)
     builtin_define ("__PPC405__");
+  /* Used by libstdc++.  */
+    builtin_define ("__NO_LWSYNC__");
   /* May be overridden by target configuration.  */
Index: gcc/config/rs6000/rs6000.h
--- gcc/config/rs6000/rs6000.h	(revision 118892)
+++ gcc/config/rs6000/rs6000.h	(working copy)
@@ -342,6 +342,9 @@
 #define TARGET_E500_SINGLE 0
 #define TARGET_E500_DOUBLE 0
+/* E500 processors only support plain "sync", not lwsync.  */
 /* Sometimes certain combinations of command options do not make sense
    on a particular target machine.  You can define a macro
    `OVERRIDE_OPTIONS' to take account of this.  This macro, if
Index: gcc/config/rs6000/
--- gcc/config/rs6000/	(revision 118892)
+++ gcc/config/rs6000/	(working copy)
@@ -615,6 +615,11 @@
   [(set (mem:BLK (match_scratch 0 "X"))
 	(unspec_volatile:BLK [(mem:BLK (match_scratch 1 "X"))] UNSPEC_LWSYNC))]
-  ".long 0x7c2004ac"
+    return "sync";
+  else
+    return ".long 0x7c2004ac";
   [(set_attr "type" "sync")])
Index: libstdc++-v3/config/cpu/powerpc/atomic_word.h
--- libstdc++-v3/config/cpu/powerpc/atomic_word.h	(revision 118892)
+++ libstdc++-v3/config/cpu/powerpc/atomic_word.h	(working copy)
@@ -33,6 +33,10 @@
 typedef int _Atomic_word;
 #define _GLIBCXX_READ_MEM_BARRIER __asm __volatile ("isync":::"memory")
+#ifdef __NO_LWSYNC__
+#define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("sync":::"memory")
 #define _GLIBCXX_WRITE_MEM_BARRIER __asm __volatile ("lwsync":::"memory")

Joseph S. Myers

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