add comment why preferred stack boundary is 4 on i386

diff --git a/arch/i386/Makefile b/arch/i386/Makefile
index 385dd52beefc1c31596b4b4e6c33a160cd6dda47..e6c99c67d8afcfdd0b0f688691e27ea2589e3e21 100644 (file)
--- a/arch/i386/Makefile
+++ b/arch/i386/Makefile
@@ -2,4 +2,6 @@
 # Build system
 # ==========================================================================
 
+# -mpreferred-stack-boundary=2 is essential in preventing gcc 4.2.x
+# from aligning stack to 16 bytes. (Which is gcc's way of supporting SSE).
 CFLAGS += $(call cc-option,-march=i386 -mpreferred-stack-boundary=2,)