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| author | Alan Modra <amodra@gmail.com> | 2019-10-26 18:38:26 +1030 |
|---|---|---|
| committer | Alan Modra <amodra@gmail.com> | 2019-10-26 20:19:28 +1030 |
| commit | 6f69abb0498286297936a178ba81c7e445aa4437 (patch) | |
| tree | 7a5d73d08dad01d2423566cffb48b48cda5971a1 /gas | |
| parent | 30baf67b6505d903bf678f9a0ba3645eb337ce49 (diff) | |
| download | gdb-6f69abb0498286297936a178ba81c7e445aa4437.zip gdb-6f69abb0498286297936a178ba81c7e445aa4437.tar.gz gdb-6f69abb0498286297936a178ba81c7e445aa4437.tar.bz2 | |
Optimise away eh_frame advance_loc 0
These can be generated when multiple cfi directives are emitted for an
instruction and the insn frag is closed off between directives, as
happens when listings are enabled. No doubt the advance_loc of zero
could be avoided by backtracking over frags in dw2gencfi.c before
calling cfi_add_advance_loc, but that seems like more work than
cleaning up afterwards as this patch does.
Noticed when looking at the testcase in PR25125.
PR 25125
* dw2gencfi.c (output_cfi_insn): Don't output DW_CFA_advance_loc+0.
* ehopt.c (eh_frame_estimate_size_before_relax): Return -1 for
an advance_loc of zero.
(eh_frame_relax_frag): Translate fr_subtype of 7 to size -1.
(eh_frame_convert_frag): Handle fr_subtype of 7. Abort on
unexpected fr_subtype.
Diffstat (limited to 'gas')
| -rw-r--r-- | gas/ChangeLog | 10 | ||||
| -rw-r--r-- | gas/dw2gencfi.c | 4 | ||||
| -rw-r--r-- | gas/ehopt.c | 18 |
3 files changed, 28 insertions, 4 deletions
diff --git a/gas/ChangeLog b/gas/ChangeLog index 8b78037..f900c26 100644 --- a/gas/ChangeLog +++ b/gas/ChangeLog @@ -1,3 +1,13 @@ +2019-10-26 Alan Modra <amodra@gmail.com> + + PR 25125 + * dw2gencfi.c (output_cfi_insn): Don't output DW_CFA_advance_loc+0. + * ehopt.c (eh_frame_estimate_size_before_relax): Return -1 for + an advance_loc of zero. + (eh_frame_relax_frag): Translate fr_subtype of 7 to size -1. + (eh_frame_convert_frag): Handle fr_subtype of 7. Abort on + unexpected fr_subtype. + 2019-10-25 Alan Modra <amodra@gmail.com> PR gas/25125 diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c index 388123f..b01e4c4 100644 --- a/gas/dw2gencfi.c +++ b/gas/dw2gencfi.c @@ -1598,7 +1598,9 @@ output_cfi_insn (struct cfi_insn_data *insn) addressT delta = S_GET_VALUE (to) - S_GET_VALUE (from); addressT scaled = delta / DWARF2_LINE_MIN_INSN_LENGTH; - if (scaled <= 0x3F) + if (scaled == 0) + ; + else if (scaled <= 0x3F) out_one (DW_CFA_advance_loc + scaled); else if (scaled <= 0xFF) { diff --git a/gas/ehopt.c b/gas/ehopt.c index 207e799..bf65602 100644 --- a/gas/ehopt.c +++ b/gas/ehopt.c @@ -482,7 +482,9 @@ eh_frame_estimate_size_before_relax (fragS *frag) gas_assert (ca > 0); diff /= ca; - if (diff < 0x40) + if (diff == 0) + ret = -1; + else if (diff < 0x40) ret = 0; else if (diff < 0x100) ret = 1; @@ -491,7 +493,7 @@ eh_frame_estimate_size_before_relax (fragS *frag) else ret = 4; - frag->fr_subtype = (frag->fr_subtype & ~7) | ret; + frag->fr_subtype = (frag->fr_subtype & ~7) | (ret & 7); return ret; } @@ -506,6 +508,8 @@ eh_frame_relax_frag (fragS *frag) int oldsize, newsize; oldsize = frag->fr_subtype & 7; + if (oldsize == 7) + oldsize = -1; newsize = eh_frame_estimate_size_before_relax (frag); return newsize - oldsize; } @@ -548,9 +552,17 @@ eh_frame_convert_frag (fragS *frag) md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 2); break; - default: + case 4: md_number_to_chars (frag->fr_literal + frag->fr_fix, diff, 4); break; + + case 7: + gas_assert (diff == 0); + frag->fr_fix -= 8; + break; + + default: + abort (); } frag->fr_fix += frag->fr_subtype & 7; |