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Fix the handling of CmpORD32{S,U} which was completely bogus and

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would have caused ppc32 to miss many uninitialised value errors.
(Change affects ppc32 only).

Also add reference to the Usenix paper.



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@4888
This commit is contained in:
Julian Seward 2005-10-07 11:08:55 +00:00
parent d1c79a1830
commit 1824baf714
1 changed files with 59 additions and 1 deletions
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60
memcheck/mc_translate.c
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@ -38,6 +38,20 @@
#include "mc_include.h"
/* 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 @@ static IRAtom* expensiveCmpEQorNE ( MCEnv* mce,
}
/* --------- Semi-accurate interpretation of CmpORD. --------- */
/* CmpORD32{S,U} does PowerPC-style 3-way comparisons:
CmpORD32S(x,y) = 1<<3 if x <s y
= 1<<2 if x >s y
= 1<<1 if x == y
and similarly the unsigned variant. The default interpretation is:
CmpORD32{S,U}#(x,y,x#,y#) = PCast(x# `UifU` y#)
& (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,
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 == Iop_CmpORD32S || cmp_op == Iop_CmpORD32U);
return
binop(
Iop_And32,
assignNew(
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 @@ IRAtom* expr2vbits_Binop ( MCEnv* mce,
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);
case Iop_Add64:
if (mce->bogusLiterals)