RFA: RX Sim: Use unsigned masks when setting flag bits

RFA: RX Sim: Use unsigned masks when setting flag bits

[Nick Clifton]

Hi Guys,

  The patch below fixes a small bug in the RX simulator.

  The b2mask[] array contains unsigned bit masks that are used to check
  for a zero result of an arithmetic, logic or comparison operation.
  But the masks were being placed into signed integers and then compared
  against a signed long long value.  This meant that if the 32-bit mask
  (0xFFFFFFFF) was being used, it would be sign-extended to 64-bits
  (0xFFFFFFFFFFFFFFFF) before being compared against the result of the
  operation.  If that operation resulted in a 64-bit value with the
  bottom 32-bits clear but the any of the top 32-bits set, then the AND
  of the mask and value would be non-zero, and so the Z bit would not be
  set.  This is despite the fact that the value that would be stored in
  the destination register would be exactly 0.

  The patch fixes the problem by using unsigned integers to hold the
  selected mask value.  Tested by building and regression testing an
  rx-elf toolchain.  This patch fixes a regression in the gcc testsuite,
  specifically the gcc.c-torture/execute/vrp-5.c test.

  OK to apply ?

Cheers
  Nick

sim/rx/ChangeLog
2010-06-07  Nick Clifton  <nickc@redhat.com>

	* reg.c (set_oszc): Use unsigned int for the mask.
	(set_szc, set_osz, set_sz): Likewise.

Index: sim/rx/reg.c
===================================================================
RCS file: /cvs/src/src/sim/rx/reg.c,v
retrieving revision 1.2
diff -c -3 -p -r1.2 reg.c
*** sim/rx/reg.c	1 Jan 2010 10:03:33 -0000	1.2
--- sim/rx/reg.c	7 Jun 2010 07:16:11 -0000
*************** set_flags (int mask, int newbits)
*** 377,383 ****
  void
  set_oszc (long long value, int b, int c)
  {
!   int mask = b2mask[b];
    int f = 0;
  
    if (c)
--- 377,383 ----
  void
  set_oszc (long long value, int b, int c)
  {
!   unsigned int mask = b2mask[b];
    int f = 0;
  
    if (c)
*************** set_oszc (long long value, int b, int c)
*** 394,400 ****
  void
  set_szc (long long value, int b, int c)
  {
!   int mask = b2mask[b];
    int f = 0;
  
    if (c)
--- 394,400 ----
  void
  set_szc (long long value, int b, int c)
  {
!   unsigned int mask = b2mask[b];
    int f = 0;
  
    if (c)
*************** set_szc (long long value, int b, int c)
*** 409,415 ****
  void
  set_osz (long long value, int b)
  {
!   int mask = b2mask[b];
    int f = 0;
  
    if ((value & mask) == 0)
--- 409,415 ----
  void
  set_osz (long long value, int b)
  {
!   unsigned int mask = b2mask[b];
    int f = 0;
  
    if ((value & mask) == 0)
*************** set_osz (long long value, int b)
*** 424,430 ****
  void
  set_sz (long long value, int b)
  {
!   int mask = b2mask[b];
    int f = 0;
  
    if ((value & mask) == 0)
--- 424,430 ----
  void
  set_sz (long long value, int b)
  {
!   unsigned int mask = b2mask[b];
    int f = 0;
  
    if ((value & mask) == 0)

Re: RFA: RX Sim: Use unsigned masks when setting flag bits

[DJ Delorie]

I wonder if the definition of b2mask[] should have "UL" on the
0xfffffff too ?  It seems to work already though ;-)

Otherwise, I think this patch is OK.

Re: RFA: RX Sim: Use unsigned masks when setting flag bits

[Nick Clifton]

Hi DJ,

> I wonder if the definition of b2mask[] should have "UL" on the
> 0xfffffff too ?  It seems to work already though ;-)

I actually tested making the array contain long long masks, since they 
were being used to test against long long values, but this broke the 
computation that determines the carry bit, so I abandoned that change.

> Otherwise, I think this patch is OK.

Thanks - committed.

Cheers
   Nick

sim/ChangeLog

	* reg.c (set_oszc): Use unsigned int for the mask.
	(set_szc, set_osz, set_sz): Likewise.