rtl.texi (sequence): Rewrite documentation to match the current use of SEQUENCE rtl...

	* 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

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a7ca045..f2d2a61 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,16 @@
+2013-04-08  Steven Bosscher  <steven@gcc.gnu.org>
+
+       * 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.
+
 2013-04-08  Teresa Johnson  <tejohnson@google.com>
 
        * basic-block.h (GCOV_COMPUTE_SCALE): Define.

diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index a9890f8..8829b0e 100644 (file)
--- a/gcc/doc/rtl.texi
+++ b/gcc/doc/rtl.texi
@@ -3099,17 +3099,10 @@ side-effects.
 
 @findex sequence
 @item (sequence [@var{insns} @dots{}])
-Represents a sequence of insns.  Each of the @var{insns} that appears
-in the vector is suitable for appearing in the chain of insns, so it
-must be an @code{insn}, @code{jump_insn}, @code{call_insn},
-@code{code_label}, @code{barrier} or @code{note}.
-
-A @code{sequence} RTX is never placed in an actual insn during RTL
-generation.  It represents the sequence of insns that result from a
-@code{define_expand} @emph{before} those insns are passed to
-@code{emit_insn} to insert them in the chain of insns.  When actually
-inserted, the individual sub-insns are separated out and the
-@code{sequence} is forgotten.
+Represents a sequence of insns.  If a @code{sequence} appears in the
+chain of insns, then each of the @var{insns} that appears in the sequence
+must be suitable for appearing in the chain of insns, i.e. must satisfy
+the @code{INSN_P} predicate.
 
 After delay-slot scheduling is completed, an insn and all the insns that
 reside in its delay slots are grouped together into a @code{sequence}.
@@ -3123,6 +3116,19 @@ the effect of the insns in the delay slots.  In such a case,
 the branch and should be executed only if the branch is taken; otherwise
 the insn should be executed only if the branch is not taken.
 @xref{Delay Slots}.
+
+Some back ends also use @code{sequence} objects for purposes other than
+delay-slot groups.  This is not supported in the common parts of the
+compiler, which treat such sequences as delay-slot groups.
+
+DWARF2 Call Frame Address (CFA) adjustments are sometimes also expressed
+using @code{sequence} objects as the value of a @code{RTX_FRAME_RELATED_P}
+note.  This only happens if the CFA adjustments cannot be easily derived
+from the pattern of the instruction to which the note is attached.  In
+such cases, the value of the note is used instead of best-guesing the
+semantics of the instruction.  The back end can attach notes containing
+a @code{sequence} of @code{set} patterns that express the effect of the
+parent instruction.
 @end table
 
 These expression codes appear in place of a side effect, as the body of
@@ -3602,28 +3608,8 @@ of debugging information.
 @item NOTE_INSN_EH_REGION_BEG
 @itemx NOTE_INSN_EH_REGION_END
 These types of notes indicate the position of the beginning and end of a
-level of scoping for exception handling.  @code{NOTE_BLOCK_NUMBER}
-identifies which @code{CODE_LABEL} or @code{note} of type
-@code{NOTE_INSN_DELETED_LABEL} is associated with the given region.
-
-@findex NOTE_INSN_LOOP_BEG
-@findex NOTE_INSN_LOOP_END
-@item NOTE_INSN_LOOP_BEG
-@itemx NOTE_INSN_LOOP_END
-These types of notes indicate the position of the beginning and end
-of a @code{while} or @code{for} loop.  They enable the loop optimizer
-to find loops quickly.
-
-@findex NOTE_INSN_LOOP_CONT
-@item NOTE_INSN_LOOP_CONT
-Appears at the place in a loop that @code{continue} statements jump to.
-
-@findex NOTE_INSN_LOOP_VTOP
-@item NOTE_INSN_LOOP_VTOP
-This note indicates the place in a loop where the exit test begins for
-those loops in which the exit test has been duplicated.  This position
-becomes another virtual start of the loop when considering loop
-invariants.
+level of scoping for exception handling.  @code{NOTE_EH_HANDLER}
+identifies which region is associated with these notes.
 
 @findex NOTE_INSN_FUNCTION_BEG
 @item NOTE_INSN_FUNCTION_BEG

diff --git a/gcc/reg-notes.def b/gcc/reg-notes.def
index db61c09..3b1d27c 100644 (file)
--- a/gcc/reg-notes.def
+++ b/gcc/reg-notes.def
@@ -172,11 +172,6 @@ REG_NOTE (CFA_WINDOW_SAVE)
    the rest of the compiler as a CALL_INSN.  */
 REG_NOTE (CFA_FLUSH_QUEUE)
 
-/* Indicates that REG holds the exception context for the function.
-   This context is shared by inline functions, so the code to acquire
-   the real exception context is delayed until after inlining.  */
-REG_NOTE (EH_CONTEXT)
-
 /* Indicates what exception region an INSN belongs in.  This is used
    to indicate what region to which a call may throw.  REGION 0
    indicates that a call cannot throw at all.  REGION -1 indicates

diff --git a/gcc/rtl.def b/gcc/rtl.def
index 5da3dd3..f8aea32 100644 (file)
--- 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.  */