qbe

commit f3301026fa404c68c7ad399b5a56a5135b88af04
parent fc124dd22e6d936de53c60f6752e45c857f10013
Author: Quentin Carbonneaux <quentin.carbonneaux@yale.edu>
Date:   Fri, 24 Feb 2017 09:42:12 -0500

reenable and fix a bug in memopt

While a minimal dead store elimination is not
implemented, the generated code looks quite a
bit better with them enabled.  It also is quite
cheap.

Diffstat:
M
main.c
 | 
2
+-
M
mem.c
 | 
5
++++-

2 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/main.c b/main.c
@@ -50,7 +50,7 @@ func(Fn *fn)
 	fillrpo(fn);
 	fillpreds(fn);
 	filluse(fn);
-	/* memopt(fn); */
+	memopt(fn);
 	ssa(fn);
 	filluse(fn);
 	ssacheck(fn);
diff --git a/mem.c b/mem.c
@@ -86,15 +86,18 @@ memopt(Fn *fn)
 				/* try to turn loads into copies so we
 				 * can eliminate them later */
 				switch(l->op) {
-				case Oload:
 				case Oloadsw:
 				case Oloaduw:
+					if (k == Kl)
+						goto Extend;
+				case Oload:
 					if (KBASE(k) != KBASE(l->cls))
 						l->op = Ocast;
 					else
 						l->op = Ocopy;
 					break;
 				default:
+				Extend:
 					l->op = Oextsb + (l->op - Oloadsb);
 					break;
 				}