Re: [PATCH] xtensa: fix MAX_ISTACK for loopgtz L32R widening

Hi Alexey,

On Tue, Aug 11, 2026 at 3:40 AM Alexey Lapshin
<[email protected]> wrote:
>
> Commit 403b0b61f6d4 ("gas: use literals/const16 for xtensa loop
> relaxation") replaced loop widening with an L32R-based sequence.
> The loopgtz variant of that sequence needs 13 istack entries, but
> MAX_ISTACK remained 12, so relaxation of an out-of-range loopgtz
> overflowed the instruction stack. Increase MAX_ISTACK and report
> overflow with as_fatal that names MAX_ISTACK. Add a test.
>
> gas/
>         * config/xtensa-istack.h (MAX_ISTACK): Increase to 16. Document
>         requirement.
>         * config/tc-xtensa.c (istack_push, istack_push_space): Report
>         stack overflow with as_fatal.
>         * testsuite/gas/xtensa/loopgtz-relax.d: New test.
>         * testsuite/gas/xtensa/loopgtz-relax.s: New test source.
> ---
>  gas/config/tc-xtensa.c                   |  8 ++++++--
>  gas/config/xtensa-istack.h               |  5 ++++-
>  gas/testsuite/gas/xtensa/loopgtz-relax.d | 16 ++++++++++++++++
>  gas/testsuite/gas/xtensa/loopgtz-relax.s | 10 ++++++++++
>  4 files changed, 36 insertions(+), 3 deletions(-)
>  create mode 100644 gas/testsuite/gas/xtensa/loopgtz-relax.d
>  create mode 100644 gas/testsuite/gas/xtensa/loopgtz-relax.s

Please resend it in a plain text form against the binutils master.

> diff --git a/gas/config/tc-xtensa.c b/gas/config/tc-xtensa.c
> index deecbb143d0..0a360223c68 100644
> --- a/gas/config/tc-xtensa.c
> +++ b/gas/config/tc-xtensa.c
> @@ -12517,7 +12517,9 @@ void
>  istack_push (IStack *stack, TInsn *insn)
>  {
>    int rec = stack->ninsn;
> -  gas_assert (!istack_full (stack));
> +  if (istack_full (stack))
> +    as_fatal (_("internal error: instruction stack overflow; "
> +               "increase MAX_ISTACK"));
>    stack->insn[rec] = *insn;
>    stack->ninsn++;
>  }
> @@ -12531,7 +12533,9 @@ istack_push_space (IStack *stack)
>  {
>    int rec = stack->ninsn;
>    TInsn *insn;
> -  gas_assert (!istack_full (stack));
> +  if (istack_full (stack))
> +    as_fatal (_("internal error: instruction stack overflow; "
> +               "increase MAX_ISTACK"));
>    insn = &stack->insn[rec];
>    tinsn_init (insn);
>    stack->ninsn++;
> diff --git a/gas/config/xtensa-istack.h b/gas/config/xtensa-istack.h
> index 524f7fa774f..cdea1700842 100644
> --- a/gas/config/xtensa-istack.h
> +++ b/gas/config/xtensa-istack.h
> @@ -23,7 +23,10 @@
>
>  #include "xtensa-isa.h"
>
> -#define MAX_ISTACK 12
> +/* Must hold the largest multi-instruction widening expansion from
> +   widen_spec_list in xtensa-relax.c.  Currently that is the loopgtz
> +   + L32R sequence (13 entries including LITERAL and LABEL).  */
> +#define MAX_ISTACK 16
>  #define MAX_INSN_ARGS 64
>
>  enum itype_enum
> diff --git a/gas/testsuite/gas/xtensa/loopgtz-relax.d b/gas/testsuite/gas/xtensa/loopgtz-relax.d
> new file mode 100644
> index 00000000000..1374186c6d6
> --- /dev/null
> +++ b/gas/testsuite/gas/xtensa/loopgtz-relax.d
> @@ -0,0 +1,16 @@
> +#as:
> +#objdump: -d
> +
> +#...
> +.*beqz.*a9,.*
> +.*bltz.*a9,.*
> +.*loopgtz.*a9,.*
> +.*rsr.lend.*a9
> +.*wsr.lbeg.*a9
> +.*l32r.*a9,.*
> +.*nop
> +.*wsr.lend.*a9
> +.*isync
> +.*rsr.lcount.*a9
> +.*addi.*a9, a9, 1
> +#...
> diff --git a/gas/testsuite/gas/xtensa/loopgtz-relax.s b/gas/testsuite/gas/xtensa/loopgtz-relax.s
> new file mode 100644
> index 00000000000..a03528f306c
> --- /dev/null
> +++ b/gas/testsuite/gas/xtensa/loopgtz-relax.s
> @@ -0,0 +1,10 @@
> +       .text
> +       .globl main
> +       .align 4
> +main:
> +       loopgtz a9, .Lloop_end
> +       .rep 200
> +       nop
> +       .endr
> +.Lloop_end:
> +       nop
> --
> 2.43.0
>


-- 
Thanks.
-- Max