From 6f69abb0498286297936a178ba81c7e445aa4437 Mon Sep 17 00:00:00 2001 From: Alan Modra Date: Sat, 26 Oct 2019 18:38:26 +1030 Subject: [PATCH] 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. --- gas/ChangeLog | 10 ++++++++++ gas/dw2gencfi.c | 4 +++- gas/ehopt.c | 18 +++++++++++++++--- 3 files changed, 28 insertions(+), 4 deletions(-) diff --git a/gas/ChangeLog b/gas/ChangeLog index 8b78037430..f900c26af4 100644 --- a/gas/ChangeLog +++ b/gas/ChangeLog @@ -1,3 +1,13 @@ +2019-10-26 Alan Modra + + 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 PR gas/25125 diff --git a/gas/dw2gencfi.c b/gas/dw2gencfi.c index 388123fd24..b01e4c4a9e 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 207e799405..bf65602f53 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; -- 2.34.1