https://sourceware.org/bugzilla/show_bug.cgi?id=32879
Jens Remus <jremus at linux dot ibm.com> changed:
What |Removed |Added
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CC| |jremus at linux dot ibm.com
--- Comment #1 from Jens Remus <jremus at linux dot ibm.com> ---
>From a s390x perspective there are a few issues with the tentative patch:
1. On s390x the initial CFA offset at function entry is 160 instead of 0.
Assuming a value of 0 is therefore wrong.
2. Using the register 6 as CFA base register in the test does not work for all
architectures. At least on s390x this is none of SP and FP and therefore the
test fails with:
Warning: skipping SFrame FDE; non-SP/FP register 6 in .cfi_def_cfa_register
A solution for the first issue may be to use the CFA offset of the current FRE,
if there is no last FRE (= previous FRE?):
> diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
> @@ -1024,6 +1024,7 @@ sframe_xlate_do_def_cfa_register (struct
> sframe_xlate_ctx *xlate_ctx,
> struct sframe_row_entry *last_fre = xlate_ctx->last_fre;
> /* Get the scratchpad FRE. This FRE will eventually get linked in. */
> struct sframe_row_entry *cur_fre = xlate_ctx->cur_fre;
> + offsetT cfa_offset = 0;
offsetT cfa_offset;
>
> gas_assert (cur_fre);
> /* Define the current CFA rule to use the provided register (but to
> @@ -1038,7 +1039,9 @@ sframe_xlate_do_def_cfa_register (struct
> sframe_xlate_ctx *xlate_ctx,
> return SFRAME_XLATE_ERR_NOTREPRESENTED; /* Not represented. */
> }
> sframe_fre_set_cfa_base_reg (cur_fre, cfi_insn->u.r);
> - sframe_fre_set_cfa_offset (cur_fre, last_fre->cfa_offset);
> + if (last_fre)
> + cfa_offset = last_fre->cfa_offset;
else
cfa_offset = cur_fre->cfa_offset;
> + sframe_fre_set_cfa_offset (cur_fre, cfa_offset);
> cur_fre->merge_candidate = false;
>
> return SFRAME_XLATE_OK;
At least that causes the correct initial CFA offset of 160 to be picked up on
s390x. But maybe cur_fre->merge_candidate needs to be factored in as well, if
both last_fre and curr_fre exist?
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