https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121964
Bug ID: 121964
Summary: aarch64: SVE predicate variables are printed
incorrectly
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: ykhrustalev at gcc dot gnu.org
Target Milestone: ---
Variables of type svbool_t are not displayed correctly in a debugger (e.g.
GDB). A debugger would read 8 bits for each predicate element (that has bitsize
1 bit) which would result in interpreting some elements incorrectly and also
reading beyond the buffer bounds.
This is due to lack of the DW_AT_bit_stride attribute in the DWARF entry for
the vector type svbool_t.
Reproducer:
```
/* File: predicate.cpp */
#include <cstdio>
#include <arm_sve.h>
[[gnu::target ("arch=armv9-a+sve")]]
void fun ()
{
// 0b ____'____'____'____'____'____'____'_111
volatile svbool_t pred8 = svwhilelt_b8_u32 (0u, 3u);
// 0b ____'____'____'____'____'____'___1'_1_1
volatile svbool_t pred16 = svwhilelt_b16_u32 (0u, 3u);
// 0b ____'____'____'____'____'___1'___1'___1
volatile svbool_t pred32 = svwhilelt_b32_u32 (0u, 3u);
// 0b ____'____'____'___1'____'___1'____'___1
volatile svbool_t pred64 = svwhilelt_b64_u32 (0u, 3u);
}
[[gnu::target("arch=armv9-a+sve")]]
int main ()
{
printf ("vector length: %lu bits\n", svcntw () * 32);
fun ();
return 0;
}
```
Compile with
```
g++ -g predicate.cpp -o predicate
```
See comments above the variables for the expected data (based on VLEN = 256
bits that gives 32 bits for the length of predicate registers): `_` means `0`
and `1` means `1`, LSB on the right.
Compare "p/t *(uint64_t*)&pred16" and "p pred16" in GDB: should show the same
data but doesn't.
Note: this was originally reported (incorrectly) as a GDB bug [1] but the issue
is on the GCC side.
[1]: https://sourceware.org/bugzilla/show_bug.cgi?id=33233
