From: Julian Seward <jseward@acm.org>
Date: Tue, 25 Jan 2005 15:47:39 +0000 (+0000)
Subject: Don't do anything special with "rep nop".  The former behaviour was to
X-Git-Tag: svn/VALGRIND_3_0_1^2~591
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d21677dc8a595a596f7e0613bcb195a810bf41fa;p=thirdparty%2Fvalgrind.git

Don't do anything special with "rep nop".  The former behaviour was to
notify the scheduler that this thread wants to yield, but that gives
such huge delays as to mess up spin-wait loops using "rep nop".  New
behaviour is to simply treat it as a no-op, with no scheduling
consequences.



git-svn-id: svn://svn.valgrind.org/vex/trunk@743
---

diff --git a/VEX/priv/guest-x86/toIR.c b/VEX/priv/guest-x86/toIR.c
index 8a30b0ac1c..2fc51e7d00 100644
--- a/VEX/priv/guest-x86/toIR.c
+++ b/VEX/priv/guest-x86/toIR.c
@@ -11286,8 +11286,14 @@ DisResult disInstr ( /*IN*/  Bool       resteerOK,
       case 0x90:           /* REP NOP (PAUSE) */
          /* a hint to the P4 re spin-wait loop */
          DIP("rep nop (P4 pause)\n");
+#        if 0
+         /* "observe" the hint.  Can cause very long delays, though. */
          jmp_lit(Ijk_Yield, ((Addr32)guest_eip_bbstart)+delta);
          whatNext = Dis_StopHere;
+#        else
+         /* act like it's a no-op */
+         whatNext = Dis_Continue;
+#        endif
          break;
 
 //--       case 0xC3:           /* REP RET */