From: simonmar <unknown>
Date: Thu, 28 Jul 2005 13:12:02 +0000 (+0000)
Subject: [project @ 2005-07-28 13:12:02 by simonmar]
X-Git-Tag: Initial_conversion_from_CVS_complete~291
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=106fcfb0003ae4555db0495904864f8921c49202;p=ghc-hetmet.git

[project @ 2005-07-28 13:12:02 by simonmar]
comments about -fno-strict-aliasing
---

diff --git a/ghc/rts/Makefile b/ghc/rts/Makefile
index 0588a5b..0d09e79 100644
--- a/ghc/rts/Makefile
+++ b/ghc/rts/Makefile
@@ -326,6 +326,10 @@ ifeq "$(Windows)" "YES"
 PrimOps_HC_OPTS += -\#include '<windows.h>' -\#include win32/AsyncIO.h
 endif
 
+# -O3 helps unroll some loops (especially in copy() with a constant argument).
+# -fno-strict-aliasing is a hack because we often mix StgPtr and StgClosure pointers
+# to the same object, and gcc will assume these don't alias.  eg. it happens in
+# copy() with gcc 3.4.3, the upd_evacee() assigments get moved before the object copy.
 GC_HC_OPTS += -optc-O3 -optc-fno-strict-aliasing
 
 # Cmm must be compiled via-C for now, because the NCG can't handle loops