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[PATCH][SH] simulator mis-executing pre-decrement
- From: Andrew STUBBS <andrew dot stubbs at st dot com>
- To: GDB Patches <gdb-patches at sourceware dot org>
- Date: Fri, 23 Feb 2007 14:54:39 +0000
- Subject: [PATCH][SH] simulator mis-executing pre-decrement
Hi,
The attached patch fixes a problem with pre-decrement store instructions
on the SH simulator.
The problem can be demonstrated with the following program:
#include <stdio.h>
int
main()
{
int i[2] = {0,0};
int *p = &i[1];
asm ("mov.l %0,@-%0\n" : "+r" (p));
if ((int*)i[0] == &i[1])
printf ("PASS: Value Correct.\n");
else
printf ("FAIL: Incorrect value written.\n");
return 0;
}
The issue is that, when both operands use the same register, the *value*
to be stored is decremented, but only the *address* of the store should
have been decremented. I.e. in the example, it is supposed to store "p"
at "p - 4", but actually stores "p - 4" at "p - 4".
Note that GCC has a similar error which means that the two work together
(probably not an accident), but the binaries may not work on real
silicon. I think a patch for this problem will be submitted to GCC
sometime soon.
:ADDPATCH sh sim:
Unfortunately, I can't test it on the latest GDB because CVS isn't
accessible (corporate IT issue), but I'm fairly sure it works in the
sources I do have. For the same reason, I'll have to ask somebody else
to do the commit for me.
Thanks
Andrew Stubbs
2007-02-22 Andrew Stubbs <andrew.stubbs@st.com>
* gencode.c (tab): Correct pre-decrement instructions when m == n.
Index: src/sim/sh/gencode.c
===================================================================
--- src.orig/sim/sh/gencode.c 2005-06-17 04:13:07.000000000 +0100
+++ src/sim/sh/gencode.c 2007-02-23 12:04:35.000000000 +0000
@@ -970,9 +970,11 @@ op tab[] =
"WBAT (R[n] + R0, R[m]);",
},
{ "n", "nm", "mov.b <REG_M>,@-<REG_N>", "0010nnnnmmmm0100",
+ /* Allow for the case where m == n. */
+ "int t = R[m];",
"MA (1);",
"R[n] -= 1;",
- "WBAT (R[n], R[m]);",
+ "WBAT (R[n], t);",
},
{ "n", "n0", "mov.b R0,@<REG_N>+", "0100nnnn10001011",
"MA (1);",
@@ -1035,9 +1037,11 @@ op tab[] =
"WLAT (R0 + R[n], R[m]);",
},
{ "n", "nm", "mov.l <REG_M>,@-<REG_N>", "0010nnnnmmmm0110",
+ /* Allow for the case where m == n. */
+ "int t = R[m];",
"MA (1) ;",
"R[n] -= 4;",
- "WLAT (R[n], R[m]);",
+ "WLAT (R[n], t);",
},
{ "n", "n0", "mov.l R0,@<REG_N>+", "0100nnnn10101011",
"MA (1) ;",
@@ -1099,9 +1103,11 @@ op tab[] =
"WWAT (R0 + R[n], R[m]);",
},
{ "n", "mn", "mov.w <REG_M>,@-<REG_N>", "0010nnnnmmmm0101",
+ /* Allow for the case where m == n. */
+ "int t = R[m];",
"MA (1);",
"R[n] -= 2;",
- "WWAT (R[n], R[m]);",
+ "WWAT (R[n], t);",
},
{ "n", "0n", "mov.w R0,@<REG_N>+", "0100nnnn10011011",
"MA (1);",