From: Julian Seward <jseward@acm.org>
Date: Sat, 22 Oct 2005 12:46:06 +0000 (+0000)
Subject: Remove inefficient and not-completely-general logic in addHRegUse and
X-Git-Tag: svn/VALGRIND_3_1_1^2~68
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d8cf652994787264818dfd302707ed2fd664eaf5;p=thirdparty%2Fvalgrind.git

Remove inefficient and not-completely-general logic in addHRegUse and
replace with something general and simpler.



git-svn-id: svn://svn.valgrind.org/vex/trunk@1423
---

diff --git a/VEX/priv/host-generic/h_generic_regs.c b/VEX/priv/host-generic/h_generic_regs.c
index 0388c6bc5a..b0d58b627a 100644
--- a/VEX/priv/host-generic/h_generic_regs.c
+++ b/VEX/priv/host-generic/h_generic_regs.c
@@ -122,15 +122,21 @@ void addHRegUse ( HRegUsage* tab, HRegMode mode, HReg reg )
       tab->n_used++;
    } else {
       /* Found: combine or ignore. */
-      if (tab->mode[i] == mode)
-         return; /* duplicate, ignore */
-      if (mode == HRmModify) {
+      /* This is a greatest-lower-bound operation in the poset:
+
+            R   W
+             \ /
+              M
+
+         Need to do: tab->mode[i] = GLB(tab->mode, mode).  In this
+         case very simple -- if tab->mode[i] != mode then result must
+         be M.
+      */
+      if (tab->mode[i] == mode) {
+         /* duplicate, ignore */
+      } else {
          tab->mode[i] = HRmModify;
-         return; /* modify mode makes previous mode irrelevant */
       }
-      vassert( (mode == HRmRead && tab->mode[i] == HRmWrite)
-              || (mode == HRmWrite && tab->mode[i] == HRmRead) );
-      tab->mode[i] = HRmModify;
    }
 }