Message ID | CABu31nNtKkovaBG4=vmMkwx_Mv_=B9WGy3LDSZG8ij4RdfGFbA@mail.gmail.com |
---|---|
State | New |
Headers | show |
On Sun, Apr 7, 2013 at 12:04 AM, Steven Bosscher <stevenb.gcc@gmail.com> wrote: > Hello, > > The existing documentation for SEQUENCE still states it is used for > DEFINE_EXPAND sequences. I think I wasn't even hacking GCC when that > practice was abandoned, and in the mean time some other uses of > SEQUENCE have appeared in the compiler. So, a long-overdue > documentation update. > > OK for trunk? Ok. Thanks, Richard. > Ciao! > Steven > > > * doc/rtl.texi (sequence): Rewrite documentation to match the > current use of SEQUENCE rtl objects. > * rtl.def (SEQUENCE): Likewise. > > Index: doc/rtl.texi > =================================================================== > --- doc/rtl.texi (revision 197532) > +++ doc/rtl.texi (working copy) > @@ -3099,18 +3099,11 @@ 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}. > +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. > > -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. > - > 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}. > The insn requiring the delay slot is the first insn in the vector; > @@ -3123,6 +3116,19 @@ the effect of the insns in the delay slots. In su > 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 > Index: rtl.def > =================================================================== > --- rtl.def (revision 197533) > +++ rtl.def (working copy) > @@ -102,10 +102,24 @@ DEF_RTL_EXPR(EXPR_LIST, "expr_list", "ee", RTX_EXT > 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. */
On Mon, Apr 8, 2013 at 11:30 AM, Richard Biener wrote: > On Sun, Apr 7, 2013 at 12:04 AM, Steven Bosscher wrote: >> Hello, >> >> The existing documentation for SEQUENCE still states it is used for >> DEFINE_EXPAND sequences. I think I wasn't even hacking GCC when that >> practice was abandoned, and in the mean time some other uses of >> SEQUENCE have appeared in the compiler. So, a long-overdue >> documentation update. >> >> OK for trunk? > > Ok. Thanks, I'm committing this along with something else I noticed: NOTE_INSN_LOOP notes don't exist anymore, and NOTE_INSN_EH_REGION notes don't have NOTE_BLOCK_NUMBER anymore but do have so-far-undocumented NOTE_EH_HANDLER. @@ -3602,29 +3608,9 @@ 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. +level of scoping for exception handling. @code{NOTE_EH_HANDLER} +identifies which region is associated with these notes. -@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. - @findex NOTE_INSN_FUNCTION_BEG @item NOTE_INSN_FUNCTION_BEG Appears at the start of the function body, after the function
Index: doc/rtl.texi =================================================================== --- doc/rtl.texi (revision 197532) +++ doc/rtl.texi (working copy) @@ -3099,18 +3099,11 @@ 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}. +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. -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. - 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}. The insn requiring the delay slot is the first insn in the vector; @@ -3123,6 +3116,19 @@ the effect of the insns in the delay slots. In su 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 Index: rtl.def =================================================================== --- rtl.def (revision 197533) +++ rtl.def (working copy) @@ -102,10 +102,24 @@ DEF_RTL_EXPR(EXPR_LIST, "expr_list", "ee", RTX_EXT 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. */