From 9fb6b620f09541d0f00e1e2f34de5401b716741f Mon Sep 17 00:00:00 2001 From: Steven Bosscher Date: Mon, 8 Apr 2013 19:59:57 +0000 Subject: rtl.texi (sequence): Rewrite documentation to match the current use of SEQUENCE rtl objects. * doc/rtl.texi (sequence): Rewrite documentation to match the current use of SEQUENCE rtl objects. * rtl.def (SEQUENCE): Likewise. * doc/rtl.texi (NOTE_INSN_EH_REGION_BEG, NOTE_INSN_EH_REGION_END): Update documentation. (NOTE_INSN_LOOP_BEG, NOTE_INSN_LOOP_END, NOTE_INSN_LOOP_CONT, NOTE_INSN_LOOP_VTOP): Remove documentation for non-existing notes. * reg-notes.def (REG_EH_CONTEXT): Remove unused note. From-SVN: r197611 --- gcc/rtl.def | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'gcc/rtl.def') diff --git a/gcc/rtl.def b/gcc/rtl.def index 5da3dd3..f8aea32 100644 --- a/gcc/rtl.def +++ b/gcc/rtl.def @@ -102,10 +102,24 @@ DEF_RTL_EXPR(EXPR_LIST, "expr_list", "ee", RTX_EXTRA) The insns are represented in print by their uids. */ DEF_RTL_EXPR(INSN_LIST, "insn_list", "ue", RTX_EXTRA) -/* SEQUENCE appears in the result of a `gen_...' function - for a DEFINE_EXPAND that wants to make several insns. - Its elements are the bodies of the insns that should be made. - `emit_insn' takes the SEQUENCE apart and makes separate insns. */ +/* SEQUENCE is used in late passes of the compiler to group insns for + one reason or another. + + For example, after delay slot filling, branch instructions with filled + delay slots are represented as a SEQUENCE of length 1 + n_delay_slots, + with the branch instruction in XEXPVEC(seq, 0, 0) and the instructions + occupying the delay slots in the remaining XEXPVEC slots. + + Another place where a SEQUENCE may appear, is in REG_FRAME_RELATED_EXPR + notes, to express complex operations that are not obvious from the insn + to which the REG_FRAME_RELATED_EXPR note is attached. In this usage of + SEQUENCE, the sequence vector slots do not hold real instructions but + only pseudo-instructions that can be translated to DWARF CFA expressions. + + Some back ends also use SEQUENCE to group insns in bundles. + + Much of the compiler infrastructure is not prepared to handle SEQUENCE + objects. Only passes after pass_free_cfg are expected to handle them. */ DEF_RTL_EXPR(SEQUENCE, "sequence", "E", RTX_EXTRA) /* Represents a non-global base address. This is only used in alias.c. */ -- cgit v1.1