| Message ID | 20120918215123.xd8ig0fdus4g0c4c-nzlynne@webmail.spamcop.net |
|---|---|
| State | New |
| Headers | show |
On Wed, Sep 19, 2012 at 3:51 AM, Joern Rennecke <amylaar@spamcop.net> wrote: > I am about to submit the ARCompact target port; this port needs a few > patches to target-independent code. > > There is a move pattern with 20 alternatives; a few of them need a simple > function call to decide which output pattern to use. With the '@'-syntax > for multi-alternative templates, each alternative is still a one-liner. > Requiring to transform this into some switch statement would make the thing > several times as big, and very hard to take in; besides, it is generally > a maintenance issue if you have to completely rewrite a multi-alternative > template if you just change one alternative from a constant to some C-code, > or vice versa for the last non-literal alternative. > > The attached patch makes the '*' syntax for C code fragments available for > individual alternatives of an '@' multi-alternative output template. > It does this by translating the input into a switch statement in the > generated file, so in a way this is just syntactic sugar, but it's syntactic > sugar that makes some machine descriptions easier to write and change. > > Bootstrapped in revision 191429 for i686-pc-linux-gnu. > > I've been wondering if it'd make sense to also support for '{' / '}' , > but at least in the ARCompact context, I think the use of that syntax > inside a multi-alternative template would reduce rather than improve > legibility, so, having no application for the '{' / '}' in that place, > there seems to be no use in adding support for that at this point in time. I think that needs to be documented somewhere in the internals manual, possibly with an example. Richard. > 2008-11-19 J"orn Rennecke <joern.rennecke@arc.com> > > * genoutput.c (process_template): Process '*' in '@' alternatives. > > Index: genoutput.c > =================================================================== > --- genoutput.c (revision 191429) > +++ genoutput.c (working copy) > @@ -662,19 +662,55 @@ process_template (struct data *d, const > list of assembler code templates, one for each alternative. */ > else if (template_code[0] == '@') > { > - d->template_code = 0; > - d->output_format = INSN_OUTPUT_FORMAT_MULTI; > + int found_star = 0; > > - printf ("\nstatic const char * const output_%d[] = {\n", > d->code_number); > + for (cp = &template_code[1]; *cp; ) > + { > + while (ISSPACE (*cp)) > + cp++; > + if (*cp == '*') > + found_star = 1; > + while (!IS_VSPACE (*cp) && *cp != '\0') > + ++cp; > + } > + d->template_code = 0; > + if (found_star) > + { > + d->output_format = INSN_OUTPUT_FORMAT_FUNCTION; > + puts ("\nstatic const char *"); > + printf ("output_%d (rtx *operands ATTRIBUTE_UNUSED, " > + "rtx insn ATTRIBUTE_UNUSED)\n", d->code_number); > + puts ("{"); > + puts (" switch (which_alternative)\n {"); > + } > + else > + { > + d->output_format = INSN_OUTPUT_FORMAT_MULTI; > + printf ("\nstatic const char * const output_%d[] = {\n", > + d->code_number); > + } > > for (i = 0, cp = &template_code[1]; *cp; ) > { > - const char *ep, *sp; > + const char *ep, *sp, *bp; > > while (ISSPACE (*cp)) > cp++; > > - printf (" \""); > + bp = cp; > + if (found_star) > + { > + printf (" case %d:", i); > + if (*cp == '*') > + { > + printf ("\n "); > + cp++; > + } > + else > + printf (" return \""); > + } > + else > + printf (" \""); > > for (ep = sp = cp; !IS_VSPACE (*ep) && *ep != '\0'; ++ep) > if (!ISSPACE (*ep)) > @@ -690,7 +726,18 @@ process_template (struct data *d, const > cp++; > } > > - printf ("\",\n"); > + if (!found_star) > + puts ("\","); > + else if (*bp != '*') > + puts ("\";"); > + else > + { > + /* The usual action will end with a return. > + If there is neither break or return at the end, this is > + assumed to be intentional; this allows to have multiple > + consecutive alternatives share some code. */ > + puts (""); > + } > i++; > } > if (i == 1) > @@ -700,7 +747,10 @@ process_template (struct data *d, const > error_with_line (d->lineno, > "wrong number of alternatives in the output > template"); > > - printf ("};\n"); > + if (found_star) > + puts (" default: gcc_unreachable ();\n }\n}"); > + else > + printf ("};\n"); > } > else > { >
Quoting Richard Guenther <richard.guenther@gmail.com>: > I think that needs to be documented somewhere in the internals manual, I suppose it should logically go to the current end of the Output Statement node in md.texi . Line 668 in revision 191429, just before the Predicates node. > possibly with an example. AFAICT the existing examples are pieces of real machine descriptions. One possibility would be the movsi_insn from the arc-4_4-20090909-branch: (define_insn "*movsi_insn" [(set (match_operand:SI 0 "move_dest_operand" "=Rcq,Rcq#q,w, w,w, w,???w, ?w, w,Rcq#q, w,Rcq, S,Us<,RcqRck,!*x,r,m,???m,VUsc") (match_operand:SI 1 "move_src_operand" " cL,cP,Rcq#q,cL,I,Crr,?Rac,Cpc,Clb,?Cal,?Cal,T,Rcq,RcqRck,Us>,Usd,m,c,?Rac,C32"))] "register_operand (operands[0], SImode) || register_operand (operands[1], SImode) || (CONSTANT_P (operands[1]) /* Don't use a LIMM that we could load with a single insn - we loose delay-slot filling opportunities. */ && !satisfies_constraint_I (operands[1]) && satisfies_constraint_Usc (operands[0]))" "@ mov%? %0,%1%& mov%? %0,%1%& mov%? %0,%1%& mov%? %0,%1 mov%? %0,%1 ror %0,((%1*2+1) & 0x3f) mov%? %0,%1 add %0,%S1 * return arc_get_unalign () ? \"add %0,pcl,%1-.+2\" : \"add %0,pcl,%1-.\"; mov%? %0,%S1%& mov%? %0,%S1 ld%? %0,%1%& st%? %1,%0%& * return arc_short_long (insn, \"push%? %1%&\", \"st%U0 %1,%0%&\"); * return arc_short_long (insn, \"pop%? %0%&\", \"ld%U1 %0,%1%&\"); ld%? %0,%1%& ld%U1%V1 %0,%1 st%U0%V0 %1,%0 st%U0%V0 %1,%0 st%U0%V0 %S1,%0" [(set_attr "type" "move,move,move,move,move,two_cycle_core,move,binary,binary,move,move,load,store,store,load,load,load,store,store,store") (set_attr "iscompact" "maybe,maybe,maybe,false,false,false,false,false,false,maybe_limm,false,true,true,true,true,true,false,false,false,false") ; Use default length for iscompact to mark length varying. But set length ; of Crr to 4. (set_attr "length" "*,*,*,4,4,4,4,8,8,*,8,*,*,*,*,*,*,*,*,8") (set_attr "cond" "canuse,canuse_limm,canuse,canuse,canuse_limm,canuse_limm,canuse,nocond,nocond,canuse,canuse,nocond,nocond,nocond,nocond,nocond,nocond,nocond,nocond,nocond")]) Although the number of different concepts combined here might a bit distract from the point. Also, it'll need steering commitee approval to put this code, which was previously contributed under the GPL (on the branch) into GFDL documentation. Or should I make up a reduced/synthetic example for a simpler - but probably pointless as an actual output template - example?
On Wed, Sep 19, 2012 at 2:06 PM, Joern Rennecke <amylaar@spamcop.net> wrote: > Quoting Richard Guenther <richard.guenther@gmail.com>: > > >> I think that needs to be documented somewhere in the internals manual, > > > I suppose it should logically go to the current end of the Output Statement > node in md.texi . Line 668 in revision 191429, just before the Predicates > node. Yes. >> possibly with an example. > > > AFAICT the existing examples are pieces of real machine descriptions. > One possibility would be the movsi_insn from the arc-4_4-20090909-branch: > > (define_insn "*movsi_insn" > [(set (match_operand:SI 0 "move_dest_operand" "=Rcq,Rcq#q,w, w,w, w,???w, > ?w, w,Rcq#q, w,Rcq, S,Us<,RcqRck,!*x,r,m,???m,VUsc") > (match_operand:SI 1 "move_src_operand" " > cL,cP,Rcq#q,cL,I,Crr,?Rac,Cpc,Clb,?Cal,?Cal,T,Rcq,RcqRck,Us>,Usd,m,c,?Rac,C32"))] > "register_operand (operands[0], SImode) > || register_operand (operands[1], SImode) > || (CONSTANT_P (operands[1]) > /* Don't use a LIMM that we could load with a single insn - we loose > delay-slot filling opportunities. */ > && !satisfies_constraint_I (operands[1]) > && satisfies_constraint_Usc (operands[0]))" > "@ > mov%? %0,%1%& > mov%? %0,%1%& > mov%? %0,%1%& > mov%? %0,%1 > mov%? %0,%1 > ror %0,((%1*2+1) & 0x3f) > mov%? %0,%1 > add %0,%S1 > * return arc_get_unalign () ? \"add %0,pcl,%1-.+2\" : \"add > %0,pcl,%1-.\"; > mov%? %0,%S1%& > mov%? %0,%S1 > ld%? %0,%1%& > st%? %1,%0%& > * return arc_short_long (insn, \"push%? %1%&\", \"st%U0 %1,%0%&\"); > * return arc_short_long (insn, \"pop%? %0%&\", \"ld%U1 %0,%1%&\"); > ld%? %0,%1%& > ld%U1%V1 %0,%1 > st%U0%V0 %1,%0 > st%U0%V0 %1,%0 > st%U0%V0 %S1,%0" > [(set_attr "type" > "move,move,move,move,move,two_cycle_core,move,binary,binary,move,move,load,store,store,load,load,load,store,store,store") > (set_attr "iscompact" > "maybe,maybe,maybe,false,false,false,false,false,false,maybe_limm,false,true,true,true,true,true,false,false,false,false") > ; Use default length for iscompact to mark length varying. But set > length > ; of Crr to 4. > (set_attr "length" "*,*,*,4,4,4,4,8,8,*,8,*,*,*,*,*,*,*,*,8") > (set_attr "cond" > "canuse,canuse_limm,canuse,canuse,canuse_limm,canuse_limm,canuse,nocond,nocond,canuse,canuse,nocond,nocond,nocond,nocond,nocond,nocond,nocond,nocond,nocond")]) > > Although the number of different concepts combined here might a bit > distract from the point. Also, it'll need steering commitee approval > to put this code, which was previously contributed under the GPL (on the > branch) into GFDL documentation. > > Or should I make up a reduced/synthetic example for a simpler - but > probably pointless as an actual output template - example? Something smaller (but pointless) woudl be nice. Richard.
Index: genoutput.c =================================================================== --- genoutput.c (revision 191429) +++ genoutput.c (working copy) @@ -662,19 +662,55 @@ process_template (struct data *d, const list of assembler code templates, one for each alternative. */ else if (template_code[0] == '@') { - d->template_code = 0; - d->output_format = INSN_OUTPUT_FORMAT_MULTI; + int found_star = 0; - printf ("\nstatic const char * const output_%d[] = {\n", d->code_number); + for (cp = &template_code[1]; *cp; ) + { + while (ISSPACE (*cp)) + cp++; + if (*cp == '*') + found_star = 1; + while (!IS_VSPACE (*cp) && *cp != '\0') + ++cp; + } + d->template_code = 0; + if (found_star) + { + d->output_format = INSN_OUTPUT_FORMAT_FUNCTION; + puts ("\nstatic const char *"); + printf ("output_%d (rtx *operands ATTRIBUTE_UNUSED, " + "rtx insn ATTRIBUTE_UNUSED)\n", d->code_number); + puts ("{"); + puts (" switch (which_alternative)\n {"); + } + else + { + d->output_format = INSN_OUTPUT_FORMAT_MULTI; + printf ("\nstatic const char * const output_%d[] = {\n", + d->code_number); + } for (i = 0, cp = &template_code[1]; *cp; ) { - const char *ep, *sp; + const char *ep, *sp, *bp; while (ISSPACE (*cp)) cp++; - printf (" \""); + bp = cp; + if (found_star) + { + printf (" case %d:", i); + if (*cp == '*') + { + printf ("\n "); + cp++; + } + else + printf (" return \""); + } + else + printf (" \""); for (ep = sp = cp; !IS_VSPACE (*ep) && *ep != '\0'; ++ep) if (!ISSPACE (*ep)) @@ -690,7 +726,18 @@ process_template (struct data *d, const cp++; } - printf ("\",\n"); + if (!found_star) + puts ("\","); + else if (*bp != '*') + puts ("\";"); + else + { + /* The usual action will end with a return. + If there is neither break or return at the end, this is + assumed to be intentional; this allows to have multiple + consecutive alternatives share some code. */ + puts (""); + } i++; } if (i == 1) @@ -700,7 +747,10 @@ process_template (struct data *d, const error_with_line (d->lineno, "wrong number of alternatives in the output template"); - printf ("};\n"); + if (found_star) + puts (" default: gcc_unreachable ();\n }\n}"); + else + printf ("};\n"); } else {
I am about to submit the ARCompact target port; this port needs a few patches to target-independent code. There is a move pattern with 20 alternatives; a few of them need a simple function call to decide which output pattern to use. With the '@'-syntax for multi-alternative templates, each alternative is still a one-liner. Requiring to transform this into some switch statement would make the thing several times as big, and very hard to take in; besides, it is generally a maintenance issue if you have to completely rewrite a multi-alternative template if you just change one alternative from a constant to some C-code, or vice versa for the last non-literal alternative. The attached patch makes the '*' syntax for C code fragments available for individual alternatives of an '@' multi-alternative output template. It does this by translating the input into a switch statement in the generated file, so in a way this is just syntactic sugar, but it's syntactic sugar that makes some machine descriptions easier to write and change. Bootstrapped in revision 191429 for i686-pc-linux-gnu. I've been wondering if it'd make sense to also support for '{' / '}' , but at least in the ARCompact context, I think the use of that syntax inside a multi-alternative template would reduce rather than improve legibility, so, having no application for the '{' / '}' in that place, there seems to be no use in adding support for that at this point in time. 2008-11-19 J"orn Rennecke <joern.rennecke@arc.com> * genoutput.c (process_template): Process '*' in '@' alternatives.