FIX validate for PPC Mac OS X - Evac.h

[ghc-hetmet.git] / rts / sm / Evac.h

diff --git a/rts/sm/Evac.h b/rts/sm/Evac.h
index c89e4d9..beaba75 100644 (file)
--- a/rts/sm/Evac.h
+++ b/rts/sm/Evac.h
@@ -4,10 +4,24 @@
  *
  * Generational garbage collector: evacuation functions
  *
+ * Documentation on the architecture of the Garbage Collector can be
+ * found in the online commentary:
+ * 
+ *   http://hackage.haskell.org/trac/ghc/wiki/Commentary/Rts/Storage/GC
+ *
  * ---------------------------------------------------------------------------*/
 
 // Use a register argument for evacuate, if available.
-#if __GNUC__ >= 2
+// Earlier, the regparm attribute was used whenever __GNUC__ >= 2, but this
+// generated warnings on PPC. So the use is restricted further.
+// See http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html that says
+//     regparm (number)
+//         On the Intel 386, the regparm attribute causes the compiler to pass
+//         arguments number one to number if they are of integral type in
+//         registers EAX, EDX, and ECX instead of on the stack. Functions that
+//         take a variable number of arguments will continue to be passed all of
+//         their arguments on the stack.
+#if __GNUC__ >= 2 && (defined(x86_64_TARGET_ARCH) || defined(i386_TARGET_ARCH))
 #define REGPARM1 __attribute__((regparm(1)))
 #else
 #define REGPARM1