[Valgrind-developers] valgrind: r4888 - trunk/memcheck

[<sv...@va...>]

Author: sewardj
Date: 2005-10-07 12:08:55 +0100 (Fri, 07 Oct 2005)
New Revision: 4888

Log:
Fix the handling of CmpORD32{S,U} which was completely bogus and
would have caused ppc32 to miss many uninitialised value errors.
(Change affects ppc32 only).

Also add reference to the Usenix paper.

Modified:
   trunk/memcheck/mc_translate.c


Modified: trunk/memcheck/mc_translate.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
--- trunk/memcheck/mc_translate.c	2005-10-07 09:49:53 UTC (rev 4887)
+++ trunk/memcheck/mc_translate.c	2005-10-07 11:08:55 UTC (rev 4888)
@@ -38,6 +38,20 @@
 #include "mc_include.h"
=20
=20
+/* This file implements the Memcheck instrumentation, and in
+   particular contains the core of its undefined value detection
+   machinery.  For a comprehensive background of the terminology,
+   algorithms and rationale used herein, read:
+
+     Using Valgrind to detect undefined value errors with
+     bit-precision
+
+     Julian Seward and Nicholas Nethercote
+
+     2005 USENIX Annual Technical Conference (General Track),
+     Anaheim, CA, USA, April 10-15, 2005.
+*/
+
 /*------------------------------------------------------------*/
 /*--- Forward decls                                        ---*/
 /*------------------------------------------------------------*/
@@ -658,6 +672,48 @@
 }
=20
=20
+/* --------- Semi-accurate interpretation of CmpORD. --------- */
+
+/* CmpORD32{S,U} does PowerPC-style 3-way comparisons:
+
+      CmpORD32S(x,y) =3D 1<<3   if  x <s y
+                     =3D 1<<2   if  x >s y
+                     =3D 1<<1   if  x =3D=3D y
+
+   and similarly the unsigned variant.  The default interpretation is:
+
+      CmpORD32{S,U}#(x,y,x#,y#) =3D PCast(x# `UifU` y#) =20
+                                  &  (7<<1)
+
+   The "& (7<<1)" reflects the fact that all result bits except 3,2,1
+   are zero and therefore defined (viz, zero).
+*/
+static IRAtom* doCmpORD32 ( MCEnv*  mce,
+                            IROp    cmp_op,
+                            IRAtom* xxhash, IRAtom* yyhash,=20
+                            IRAtom* xx,     IRAtom* yy )
+{
+   tl_assert(isShadowAtom(mce,xxhash));
+   tl_assert(isShadowAtom(mce,yyhash));
+   tl_assert(isOriginalAtom(mce,xx));
+   tl_assert(isOriginalAtom(mce,yy));
+   tl_assert(sameKindedAtoms(xxhash,xx));
+   tl_assert(sameKindedAtoms(yyhash,yy));
+   tl_assert(cmp_op =3D=3D Iop_CmpORD32S || cmp_op =3D=3D Iop_CmpORD32U)=
;
+
+   return=20
+      binop(=20
+         Iop_And32,=20
+         assignNew(=20
+            mce,Ity_I32,
+            mkPCastTo( mce,Ity_I32,
+                       assignNew( mce,Ity_I32,
+                                  mkUifU32(mce, xxhash,yyhash))) ),
+         mkU32(7<<1)
+      );
+}
+
+
 /*------------------------------------------------------------*/
 /*--- Emit a test and complaint if something is undefined. ---*/
 /*------------------------------------------------------------*/
@@ -1752,9 +1808,11 @@
=20
       cheap_AddSub32:
       case Iop_Mul32:
+         return mkLeft32(mce, mkUifU32(mce, vatom1,vatom2));
+
       case Iop_CmpORD32S:
       case Iop_CmpORD32U:
-         return mkLeft32(mce, mkUifU32(mce, vatom1,vatom2));
+         return doCmpORD32(mce, op, vatom1,vatom2, atom1,atom2);
=20
       case Iop_Add64:
          if (mce->bogusLiterals)