From 246caf35261dcae10df9f9cc936e129140958bb8 Mon Sep 17 00:00:00 2001
From: Jonas Maebe <jonas@freepascal.org>
Date: Tue, 11 Mar 2014 23:18:45 +0000
Subject: [PATCH] * never alias/coalesce cpu registers that are not usable by
the register allocator (such as stack/framepointers) with virtual
registers, otherwise they can get changed in case the virtual register
gets changed (read-only use would be ok, but we don't keep track of which
virtual registers are only read
git-svn-id: trunk@27104 -
---
compiler/rgobj.pas | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/compiler/rgobj.pas b/compiler/rgobj.pas
index 4c6f51f6de..1ffed1a52e 100644
--- a/compiler/rgobj.pas
+++ b/compiler/rgobj.pas
@@ -1121,6 +1121,15 @@ unit rgobj;
procedure trgobj.set_alias(u,v:Tsuperregister);
begin
+ { don't make registers that the register allocator shouldn't touch (such
+ as stack and frame pointers) be aliases for other registers, because
+ then it can propagate them and even start changing them if the aliased
+ register gets changed }
+ if ((u<first_imaginary) and
+ not(u in usable_register_set)) or
+ ((v<first_imaginary) and
+ not(v in usable_register_set)) then
+ exit;
include(reginfo[v].flags,ri_coalesced);
if reginfo[v].alias<>0 then
internalerror(200712291);
@@ -1272,9 +1281,15 @@ unit rgobj;
add_worklist(u);
add_worklist(v);
end
- {Next test: is it possible and a good idea to coalesce??}
- else if ((u<first_imaginary) and adjacent_ok(u,v)) or
- conservative(u,v) then
+ {Next test: is it possible and a good idea to coalesce?? Note: don't
+ coalesce registers that should not be touched by the register allocator,
+ such as stack/framepointers, because otherwise they can be changed }
+ else if (((u<first_imaginary) and adjacent_ok(u,v)) or
+ conservative(u,v)) and
+ ((u>first_imaginary) or
+ (u in usable_register_set)) and
+ ((v>first_imaginary) or
+ (v in usable_register_set)) then
begin
m.moveset:=ms_coalesced_moves; {Move coalesced!}
coalesced_moves.insert(m);