Re: [GSoC] decision tree first steps

[Prathamesh Kulkarni <bilbotheelffriend at gmail dot com>]

On Thu, Jun 19, 2014 at 2:37 PM, Prathamesh Kulkarni
<bilbotheelffriend@gmail.com> wrote:
> On Wed, Jun 18, 2014 at 4:27 PM, Richard Biener
> <richard.guenther@gmail.com> wrote:
>> On Wed, Jun 18, 2014 at 11:21 AM, Prathamesh Kulkarni
>> <bilbotheelffriend@gmail.com> wrote:
>>> On Tue, Jun 17, 2014 at 3:15 PM, Richard Biener
>>> <richard.guenther@gmail.com> wrote:
>>>>
>>>> On Tue, Jun 17, 2014 at 12:21 AM, Prathamesh Kulkarni
>>>> <bilbotheelffriend@gmail.com> wrote:
>>>> > On Mon, Jun 16, 2014 at 4:45 PM, Richard Biener
>>>> > <richard.guenther@gmail.com> wrote:
>>>> >>
>>>> >> > * Patterns requiring GENERIC support like cond_expr
>>>> >> > I am not sure about how to handle these patterns. I was thinking about
>>>> >> > handling them after we have
>>>> >> > GENERIC code generation in place.
>>>> >>
>>>> >> Yeah, though handling GENERIC for matching is as simple as
>>>> >> emitting the code check twice, the 2nd check off the an else
>>>> >> from the if (TREE_CODE (op) == SSA_NAME).  That is,
>>>> >> arrange for expr::gen_gimple_match_dt to emit
>>>> >>
>>>> >>    if (TREE_CODE (...) == SSA_NAME)
>>>> >>      {
>>>> >>         gimple def_stmt = SSA_NAME_DEF_STMT (...);
>>>> >>         if (is_gimple_assign (def_stmt) && gimple_assign_rhs_code
>>>> >> (def_stmt) == <code>)
>>>> >>           {
>>>> >>   ....
>>>> >>      }
>>>> >>    else (TREE_CODE (...) == <code>)
>>>> >>      {
>>>> >>   ....
>>>> >>      }
>>>> >>
>>>> >> which would require some refactoring in the generator.  As for refactoring
>>>> >> it I'd not hook the gen_gimple_match_dt off the AST operands but
>>>> >> inline it in the decision tree traversal routine - that also makes the
>>>> >> commoning above easier.
>>>> > Thanks, I shall get started on this.
>>>>
>>>> Good.  You also miss the special-casing of REALPART_EXPR,
>>>> IMAGPART_EXPR, VIEW_CONVERT_EXPR and BIT_FIELD_REF
>>>> operand extraction as you say below.
>>>>
>>>> >>
>>>> >> Btw, I checked what we generate for (bogus)
>>>> >>
>>>> >> (match_and_simplify
>>>> >>   (MINUS_EXPR (PLUS_EXPR@2 @0 @1) @2)
>>>> >>   @1)
>>>> >>
>>>> >> and the DT looks like
>>>> >>
>>>> >> root, 1
>>>> >> |--operand: MINUS_EXPR, 1
>>>> >> |----operand: true, 1
>>>> >> |------operand: PLUS_EXPR, 1
>>>> >> |--------operand: true, 1
>>>> >> |----------operand: true, 1
>>>> >> |------------operand: match(1), 1
>>>> >> |--------------simplify_0, 0
>>>> >>
>>>> >> though I expected
>>>> >>
>>>> >> root, 1
>>>> >> |--operand: MINUS_EXPR, 1
>>>> >> |----operand: PLUS_EXPR, 1
>>>> >> |------operand: true, 1
>>>> >> |--------operand: true, 1
>>>> >> |----------operand: match(1), 1
>>>> >> |------------simplify_0, 0
>>>> >>
>>>> >> that is, I wonder where the extra "true" comes from.
>>>> > Thanks, fixed it in the current patch.
>>>>
>>>> Thanks.
>>>>
>>>> >>
>>>> >>
>>>> >> For
>>>> >>
>>>> >> (match_and_simplify
>>>> >>   (MINUS_EXPR @2 (PLUS_EXPR@2 @0 @1))
>>>> >>   @1)
>>>> >>
>>>> >> I get
>>>> >>
>>>> >> root, 1
>>>> >> |--operand: MINUS_EXPR, 1
>>>> >> |----operand: true, 1
>>>> >> |------operand: match(1), 1
>>>> >> |--------operand: PLUS_EXPR, 1
>>>> >> |----------operand: true, 1
>>>> >> |------------operand: true, 1
>>>> >> |--------------simplify_0, 0
>>>> >>
>>>> >> which looks good to me.
>>>> >>
>>>> >> There is still a fallthru for all match failures but the DT should ensure
>>>> >> that once any of the checks is false we can terminate - that is,
>>>> >> we never have to backtrack.  Sth simple like
>>>> >>
>>>> >> --- genmatch.c.orig     2014-06-16 12:57:38.401890454 +0200
>>>> >> +++ genmatch.c  2014-06-16 12:58:03.451888730 +0200
>>>> >> @@ -816,6 +816,7 @@
>>>> >>    unsigned i;
>>>> >>    for (i = 0; i < kids.length (); ++i)
>>>> >>      kids[i]->gen_gimple (f);
>>>> >> +  fprintf (f, "return false;\n");
>>>> >>
>>>> >>
>>>> >>    for (i = 0; i < n_braces; ++i)
>>>> >>      fprintf (f, "}\n");
>>>> >>
>>>> >> So overall I think we are ok sofar and don't need major changes in
>>>> >> the algorithm.
>>>> >>
>>>> >> I'd say add the missing call support and we're good to go ripping out
>>>> >> the non-decision tree path.
>>>> >>
>>>> >> I'm happy to do some of the refactoring that I'd like to see myself
>>>> >> so you can concentrate on pattern implementing for phase 2.  But
>>>> >> feel free to do some of it yourself.
>>>> >>
>>>> >> > Small point: I was wondering if it's a good idea to slightly change
>>>> >> > the syntax of pattern to sth like:
>>>> >> > match-expression -> transform  ?
>>>> >> > eg:
>>>> >> > (minus (plus @0 @1) @1) -> @0
>>>> >> > Looks smaller -:)
>>>> >>
>>>> >> Well, I suppose we stay with what we have here.
>>>> > The attached patch, adds support for built-in functions, and fixes
>>>> > insertion bug in decision tree.
>>>> > The insertion in decision tree is carried out during preorder traversal
>>>> > of AST (insert_operand), so it avoids generating preorder traversal in
>>>> > vector (removed walk_operand_preorder and
>>>> > lower_capture). For now have put (parent, pos, preorder_level) in
>>>> > separate struct operand_info, and added instance
>>>> > of this struct to operand (struct operand_info opinfo). operand_info
>>>> > is computed during preorder traversal
>>>> > (insert_operand), so parsing routines are not concerned with it.
>>>> > Eventually we should probably move
>>>> > matching code on decision tree nodes. For convenience of tracking
>>>> > patterns, I have numbered them in match.pd.
>>>>
>>>> Ok.
>>>>
>>>> > * Testing
>>>> > Total patterns in match.pd - 58
>>>> > Total test cases: 4 (match-1.c), 32 (match-decision-tree.c), match-2.c
>>>> > is screwed.
>>>>
>>>> How is it screwed?  I see it all pass ...
>>> The regexes are not written correctly.
>>> Multiple patterns have same regex in scan-tree-dump, so even if a
>>> particular test-case fails in isolation,
>>> it shows PASS when placed with other tests that are known to PASS.
>>
>> Ah ... bummer.  Probably a good opportunity to split the testcase
>> into multiple files.
>>
>>>> > Out of 22 remaining patterns:
>>>> > Not supported yet (require GENERIC support or special handling): 31
>>>> > (convert), 33, 34, 35 (realpart/imagpart), 37 (cond)
>>>> > Not able to write test-cases: 2, 16, 31, 38
>>>>
>>>> Sth like
>>>>
>>>> char *foo (char *p)
>>>> {
>>>>   int i = 0;
>>>>   return p + i;
>>>> }
>>>>
>>>> for 2) and using -fdump-tree-ccp1-details and scanning the
>>>> ccp1 dump for "Match-and-simplified definition of _4 to p_3(D)"
>>>> (ok, that's a quite non-informative dump message and we should
>>>> improve it ... ok, changed now to "Match-and-simplified p_3(D) + _2 to p_3(D)")
>>>>
>>>> 16) is expected (it would be possible to write a testcase but I'm not sure
>>>> we want to retain that pattern).  31) has a testcases in gcc.dg/pr58742-[123].c
>>>> At some point (well, maybe now ...) we want to remove those patterns
>>>> we implemented in match.pd from the manual code in tree-ssa-forwprop.c
>>>> so we don't see "false" passing of testcases written for them.
>>>> For 38) I have no idea how to get a FMA_EXPR with integer types ... probably
>>>> the pattern (and the corresponding code in fold-const.c) is "dead".
>>>
>>> There's a serious flaw in the previous patch.
>>> For these two (match) expressions:
>>> (minus @0 @1)
>>> (minus negate @1)
>>>
>>> AST1:   minus - @0 - @1
>>> AST2:   minus - negate - @1
>>>
>>> the decision tree is:
>>>              minus
>>>              /       \
>>>           negate  true
>>>             |           |
>>>            true      true
>>>
>>> However, the way it's implemented, negate's parent (AST2's minus), is
>>> *not* present in the decision tree (because the minus of AST1 is
>>> present in decision tree, and both minus nodes compare equal). Because
>>> both minus nodes have same opinfo contents (pos, level), it "works". A
>>> change to opinfo contents, which is different for both minus nodes,
>>> would break it. This is rather ugly.
>>
>> Oops.
>>
>>> I guess we first need to decouple operand_info from AST.
>>>
>>> Approach 1:
>>> We have struct operand_info, which stores whatever information is
>>> required to generate code for that operand.
>>> Keep that in dt_operand, and add a "parent" node that points to the
>>> decision tree node that the AST parent is mapped to.
>>> We are not relying anymore on parent in AST, but on the decision tree
>>> node, the parent is mapped to,
>>> which is same for equal comparing AST nodes.
>>>
>>> struct dt_operand
>>> {
>>>   operand *op;
>>>   operand_info opinfo;
>>>   dt_operand *parent;
>>> };
>>>
>>> and pass opinfo to code-generators in AST.
>>>
>>> struct operand {
>>>   ...
>>>   virtual unsigned gen_gimple_match_dt (FILE *, const char *opname,
>>> const operand_info&);
>>> };
>>>
>>> Approach 2:
>>> Keep separate representation of decision tree from AST.
>>> This would require mirroring some AST classes (dt_predicate, dt_expr, etc.).
>>> But the code-gen for matching is off the decision tree, and only
>>> transform code-gen
>>> is off the AST.
>>>
>>> Sth like:
>>> struct dt_operand
>>> {
>>>   operand *op;
>>>   operand_info opinfo;
>>>   dt_operand *parent;
>>>
>>>   virtual void gen_gimple (FILE *)  = 0;  // generate matching code
>>> };
>>>
>>> struct dt_expr: public dt_operand
>>> {
>>>   virtual void gen_gimple (FILE *);
>>> };
>>>
>>> struct dt_pred: public dt_operand
>>> {
>>>   virtual void gen_gimple (FILE *);
>>> };
>>>
>>> struct dt_true: ...
>>> struct dt_match ...
>>
>> I like approach 2 more but I wonder if we really need to subclass
>> dt_operand.  I think that the actual code-gen is easier to follow
>> if we do sth like
>>
>> dt_operand::gen_gimple ()
>> {
>>   switch (op->op_type)
>>     {
>>     case OP_EXPR:
>> ...
>>
>> not sure why I thought that using virtual methods is a good design
>> for the matching part.
>>
>>> * GENERIC code-gen.
>>> Walk the expression node twice:
>>> (expr-code operand0 operand1)
>>>
>>> if (TREE_CODE (o<preorder level>) == SSA_NAME)
>>>   {
>>>     gimple def_stmt<preorder level> = SSA_NAME_DEF_STMT (o<preorder level>);
>>>     if (is_gimple_assign (def_stmt<level>) && gimple_assign_rhs_code
>>> (def_stmt<level>) == expr-code)
>>>       {
>>>            // generate code for children and get child with gimple_assign_rhs
>>>       }
>>>   }
>>> else if (TREE_CODE (o<preorder level>) == expr-code)
>>>   {
>>>           // generate code for children and get child with TREE_OPERAND
>>>   }
>>>
>>> However this duplicates the code of operands.
>>
>> Yeah, for very deep DTs this could badly explode exponentially ...
>>
>>> Maybe we can get children of expression when we generate code for
>>> expr-node and store it in a "temps" array
>>> and then assign element of temps array to o<operand-level> when we
>>> generate code for operand-node.
>>> This is because at expr-node we don't know the preorder level of the
>>> child, else,
>>> we would have done - o<level> = gimple_assign_rhs() or o<level> =
>>> TREE_OPERAND ()
>>>
>>> tree temps[level-max][3]; // 3 is max number of operands an expression can have
>>> Keeping it 2d array, to avoid value getting overwritten by an inner expression.
>>> level-max  = level of AST that is greater than level of all other
>>> AST's. (or maybe we can assign a value which shall be a sufficient
>>> upper-bound like 4 for captures).
>>>
>>> example:
>>> consider binary expression with two operands:
>>>
>>> if (TREE_CODE (o<expr-level>) == SSA_NAME)
>>>   {
>>>      gimple def_stmt<expr-level> = SSA_NAME_DEF_STMT (o<expr-level>);
>>>      if (is_gimple_assign (def_stmt<expr-level>) &&
>>> gimple_assign_rhs_code (def_stmt<expr-level>) == expr-code)
>>>         {
>>>            temps[expr-level][0] = gimple_assign_rhs1 (def_stmt<expr-level>);
>>>            temps[expr-level][1] = gimple_assign_rhs2 (def_stmt<expr-level>);
>>>         }
>>>   }
>>> else if (TREE_CODE o<level> == expr-code)
>>>   {
>>>      temps[expr-level][0] = TREE_OPERAND (o<expr-level>, 0);
>>>      temps[expr-level][1] = TREE_OPERAND (o<expr-level>, 1);
>>>   }
>>> else
>>>     goto L0;   // gimple/generic variant's don't match go for next
>>> "sibling" pattern
>>>
>>> if (do_valueize (temps[expr-level][0]))
>>>   if (do_valueize (temps[expr-level][1]))
>>>     {
>>>        tree o<operand-1 level> = temps[expr-level][0];  // instead of
>>> o<operand-1 level> = gimple_assign_rhs1 ();
>>>        // generate code for operand-1
>>>
>>>            tree o<operand-2 level> = temps[expr-level][1];
>>>            // generate code for operand-2
>>>
>>>                <simplify>
>>>                return true;
>>>     }
>>>
>>> L0:
>>> // next pattern
>>
>> Hmm.  Actually we know exactly when we want to match GENERIC
>> and when we want to match SSA GIMPLE.  We want to match
>> GENERIC when we want to match REALPART_EXPR, IMAGPART_EXPR,
>> VIEW_CONVERT_EXPR and BIT_FIELD_REF _or_ when the parent(!)
>> matched for COND_EXPR and we are looking at its first operand
>> (yeah, I know ...).
>>
>> So we can decide at code-gen time what code to emit.
> The attached patch separates decision tree from AST, (removes the
> "parent bug") and attempts to
> add support for special case patterns requiring GENERIC (however it
> fails one test in match-1.c, I am looking
> into that). Code-gen for matching is off the decision tree and
> code-gen for transform is off the AST.
>
> * Representation of decision tree
> dt_operand is used for representing AST operand / true / match in the
> decision tree,
> dt_operand::parent points to the decision tree node, the AST parent is
> mapped to, not the pre-order predecessor.
> dt_operand::pos gives the operand number (0th operand, 1st operand,
> etc. of parent etc.)
> I have also clubbed true and match in the same class, because true
> does not require additional fields,
> and match has only one additional field (unsigned m_level).
>
> For the following pairs of (bogus) patterns:
> (plus @0 (bit_not@2 @1))
> (plus @1 (bit_not@3 @0))
>
> It builds following decision tree:
> (type, address, level, n_kids)
>
> root (0x1513550), 0, 1
> |--PLUS_EXPR (0x1502370), 1, 1
> |----true (0x15023f0), 2, 1
> |------BIT_NOT_EXPR (0x1502470), 3, 1
> |--------true (0x15024f0), 4, 2
> |----------simplify_0 { 2, 4, 3, 4294967295,  }  (0x1512540), 5, 0
> |----------simplify_1 { 4, 2, 4294967295, 3,  }  (0x15125c0), 5, 0
>
> and for the following pairs of (bogus) patterns:
> (plus (minus@0 @1 @2) @3)
> (plus (minus @0 @1) @2)
>
> It builds following tree:
> root (0x10e2520), 0, 1
> |--PLUS_EXPR (0x10d1370), 1, 1
> |----MINUS_EXPR (0x10d13f0), 2, 1
> |------true (0x10d1470), 3, 1
> |--------true (0x10d14f0), 4, 1
> |----------true (0x10e1540), 5, 2
> |------------simplify_0 { 2, 3, 4, 5,  }  (0x10e15c0), 6, 0
> |------------simplify_1 { 3, 4, 5, 4294967295,  }  (0x10e1640), 6, 0
>
> Is that correct ?
>
> * Code-gen
> The code-gen is mostly same, with following changes:
>
> a) Generation of expressions:
> At expr-node, the children are immediately assigned in temporaries
> (t0, t1 ,...),
> and when we come at child node, the temporary is assigned to child
> node (o<level> = t<count>).
> Temporary names are stored in dt_operand::temps vector.
>
> b) Is the following condition correct  (considering for convert) ?:
>
> if (is_gimple_assign (def_stmt) &&
>     (gimple_assign_rhs_code (def_stmt) == <expr-code>
>     || CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))))
>  {
>      // generated code for operands
>  }
oops, that's only for CONVERT_EXPR and NOP_EXPR.
Fixed in the current patch

Thanks and Regards,
Prathamesh
>
> Example:
> For the pattern:
> (match_and_simplify
>   (minus (plus @0 @1) @1)
>   @0)
>
> It generated following code: http://pastebin.com/5QdCiZNi
>
> c) REALPART_EXPR / IMAGPART_EXPR / VIEW_CONVERT_EXPR / BIT_FIELD_REF:
> For these patterns, we generate GENERIC instead of GIMPLE to obtain operands ?
>
> Example:
> for the pattern:
> (match_and_simplify
>   (complex (realpart @0) (imagpart @0))
>   @0)
>
> it generated following code: http://pastebin.com/qXjEavDu
>
> d) COND_EXPR
> We generate GENERIC for 1st operand of COND_EXPR and not for the other
> operands (2nd, 3rd).
> Is that correct ?
>
> for the pattern:
> (match_and_simplify
>   (cond (bit_not @0) @1 @2)
>   (cond @0 @2 @1))
>
> it generates following code: http://pastebin.com/vL1dcb2E
>
> * GENERIC code generation.
> So far we are generating code for match-and-simplify on gimple.
> How do we start with GENERIC code-gen ?
>
> a) generate in gimple-match.c (or keep a different generic-match.c) ?
> b) Interface to GENERIC match_and_simplify - I guess it would be same as
> fold_binary / fold_unary ?
> c) We already have matching code in place for GENERIC
> (dt_operand::gen_generic_expr),
> we shall need to add code for generating GENERIC transforms.
>
> Thanks and Regards,
> Prathamesh
>
>>
>> Richard.
>>
>>> Thanks and Regards,
>>> Prathamesh
>>>
>>>>
>>>> Thanks,
>>>> Richard.
>>>>
>>>> > I will add test-cases for remaining patterns shortly.
>>>> >
>>>> > Thanks and Regards,
>>>> > Prathamesh
>>>> >>
>>>> >> Thanks,
>>>> >> Richard.
>>>> >>
>>>> >> > Thanks and Regards
>>>> >> > Prathamesh
>>>> >> >>
>>>> >> >> Richard.
>>>> >> >>
>>>> >> >>>and for the commutative variant:
>>>> >> >>>(plus (negate@0 @1) @0) S
>>>> >> >>>
>>>> >> >>>the decision tree would be the following: ?
>>>> >> >>>plus - negate - true - true - match (3) - simplify
>>>> >> >>>
>>>> >> >>>Thanks and Regards,
>>>> >> >>>Prathamesh
>>>> >> >>>>
>>>> >> >>>> Richard.
>>>> >> >>>>
>>>> >> >>>>>> Richard.
>>>> >> >>>>>>
>>>> >> >>>>>>>> There are also opportunities to optimize the generated code, but
>>>> >> >>>>>>>> basic correctness first I guess.
>>>> >> >>>>>>>>
>>>> >> >>>>>>>> I suppose we have to work a bit on the capture stuff.
>>>> >> >>>>>>>>
>>>> >> >>>>>>>> Btw, you can easily play with the code generator by doing inside
>>>> >> >>>>>>>> the gcc build directory
>>>> >> >>>>>>>>
>>>> >> >>>>>>>> obj/gcc> build/genmatch test.pd > test.c
>>>> >> >>>>>>>>
>>>> >> >>>>>>>> with a small test.pd. I used the following for the above
>>>> >> >>>examples:
>>>> >> >>>>>>>>
>>>> >> >>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>   (MINUS_EXPR (PLUS_EXPR @0 @1) @0)
>>>> >> >>>>>>>>   @1)
>>>> >> >>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>   (MINUS_EXPR (PLUS_EXPR @1 @0) @0)
>>>> >> >>>>>>>>   @1)
>>>> >> >>>>>>
>>>> >> >>>>>>>> Richard.
>>>> >> >>>>>>>>
>>>> >> >>>>>>>>>> I will change this to have capture per pattern
>>>> >> >>>>>>>>>> tree captures1[4] = {};  // for pattern-1
>>>> >> >>>>>>>>>> tree captures2[4] = {};
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> Hmm, is this the matching captures issue I mentioned?  Btw, I
>>>> >> >>>see
>>>> >> >>>>>>>>> you do
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> +void
>>>> >> >>>>>>>>> +walk_operand_preorder(vec<operand *>& operands, operand *op)
>>>> >> >>>>>>>>> +{
>>>> >> >>>>>>>>> +  if (op->type == operand::OP_CAPTURE || op->type ==
>>>> >> >>>>>>>>> operand::OP_PREDICATE || op->type == operand::OP_C_EXPR)
>>>> >> >>>>>>>>> +    {
>>>> >> >>>>>>>>> +      operands.safe_push (op);
>>>> >> >>>>>>>>> +      return;
>>>> >> >>>>>>>>> +    }
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> but that leaves captured expressions as a single operand?
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> (plus (minus@1 @2 @3) @2)
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> would have a decision tree
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>>  plus -> minus -> @2
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> correct?
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>>> d) Matching multiple patterns.
>>>> >> >>>>>>>>>> Code for patterns with same match, but different transforms is
>>>> >> >>>>>>>>>> generated as follows:
>>>> >> >>>>>>>>>> code for match operand.
>>>> >> >>>>>>>>>> if (if-expr of pattern-1)
>>>> >> >>>>>>>>>> {
>>>> >> >>>>>>>>>>   code for result of pattern-1
>>>> >> >>>>>>>>>>   return true;
>>>> >> >>>>>>>>>> }
>>>> >> >>>>>>>>>> if (if-expr of pattern-2)
>>>> >> >>>>>>>>>> {
>>>> >> >>>>>>>>>>   code for result of pattern-2
>>>> >> >>>>>>>>>>   return true;
>>>> >> >>>>>>>>>> }
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> good.
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>>> ...
>>>> >> >>>>>>>>>> Should we emit a warning for patterns that have same match
>>>> >> >>>operand but
>>>> >> >>>>>>>>>> no if-expr and no manual transform ?
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> for eg:
>>>> >> >>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>   (plus (minus @0 @1) @1)
>>>> >> >>>>>>>>>>   @0
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>   (plus (minus @0 @1) @1)
>>>> >> >>>>>>>>>>   @1  // just for illustration
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> Since the matching is ambiguous (same match, no if-expr, no
>>>> >> >>>manual
>>>> >> >>>>>>>>>> transform).
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> Yeah, I suppose we should.
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>>> we are left to choose between result of pattern-1 and result of
>>>> >> >>>>>>>>>> pattern-2.
>>>> >> >>>>>>>>>> We can emit warning and choose result of pattern-1 (first-match
>>>> >> >>>rule
>>>> >> >>>>>>>>>> as in flex).
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> e) Non-matching captures:
>>>> >> >>>>>>>>>> Haven't thought about this yet.
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> * Should we add "negative" predicates that match only if the
>>>> >> >>>predicate
>>>> >> >>>>>>>>>> fails ?
>>>> >> >>>>>>>>>> for eg:
>>>> >> >>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>   trunc_mod integer_zerop@0 !integer_zerop)
>>>> >> >>>>>>>>>>   @0)
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> well, there could simply be a integer_not_zerop predicate.
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>>> * Testing
>>>> >> >>>>>>>>>> Sorry to bring this up again, but I am still not clear what
>>>> >> >>>regex to
>>>> >> >>>>>>>>>> write in scan-tree-dump.
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> Suppose we have these two patterns in match.pd:
>>>> >> >>>>>>>>>> /* (x + y) - y -> x */
>>>> >> >>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>   (minus (plus @0 @1) @1)
>>>> >> >>>>>>>>>>   @0)
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> /* (x - y) + y -> x */
>>>> >> >>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>   (plus (minus @0 @1) @1)
>>>> >> >>>>>>>>>>   @0)
>>>> >> >>>>>>>>>> scan-tree-dump "gimple_match_and_simplified to \[^\n\r\]*=
>>>> >> >>>>>>>>>> x_\\d\+\\(D\\)"
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> I have following test-cases:
>>>> >> >>>>>>>>>> int f1(int x, int y)
>>>> >> >>>>>>>>>> {
>>>> >> >>>>>>>>>>   int t1 = x + y;
>>>> >> >>>>>>>>>>   return t1 - y;
>>>> >> >>>>>>>>>> }
>>>> >> >>>>>>>>>> scan-tree-dump "gimple_match_and_simplified to \[^\n\r\]*=
>>>> >> >>>>>>>>>> x_\\d\+\\(D\\)"
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> int f2(int x, int y)
>>>> >> >>>>>>>>>> {
>>>> >> >>>>>>>>>>   int t1 = x - y;
>>>> >> >>>>>>>>>>   return t1 + y;
>>>> >> >>>>>>>>>> }
>>>> >> >>>>>>>>>> scan-tree-dump "gimple_match_and_simplified to \[^\n\r\]*=
>>>> >> >>>>>>>>>> x_\\d\+\\(D\\)"
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> both the test-cases have same regex.
>>>> >> >>>>>>>>>> Tested in isolation f1 passes (first pattern if fired) and f2
>>>> >> >>>fails
>>>> >> >>>>>>>>>> (second pattern doesn't fire, it does after
>>>> >> >>>>>>>>>> adding it's commutative variant, but that's irrelevant for this
>>>> >> >>>case).
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> However when both test-cases are put in one file both the test
>>>> >> >>>cases
>>>> >> >>>>>>>>>> PASS.
>>>> >> >>>>>>>>>> I think that's because both of them have same regex:
>>>> >> >>>\[^\n\r\]*=
>>>> >> >>>>>>>>>> x_\\d\+\\(D\\)
>>>> >> >>>>>>>>>> so in f1 and f2's regex both match the dump for f1 function in
>>>> >> >>>>>>>>>> forwprop dump file:
>>>> >> >>>>>>>>>> "gimple_match_and_simplified to \[^\n\r\]*= x_\\d\+\\(D\\)
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> As a quick hack i rewrote f1 and f2 as:
>>>> >> >>>>>>>>>> int f1(int x, int y)
>>>> >> >>>>>>>>>> {
>>>> >> >>>>>>>>>>   int t1 = x + y;
>>>> >> >>>>>>>>>>   int f1_val = t1 - y;
>>>> >> >>>>>>>>>>   return f1_val;
>>>> >> >>>>>>>>>> }
>>>> >> >>>>>>>>>> scan-tree-dump "gimple_match_and_simplified to f1_val_\\d\+ =
>>>> >> >>>>>>>>>> x_\\d\+\\(D\\)"
>>>> >> >>>>>>>>>>
>>>> >> >>>>>>>>>> int f2(int x, int y)
>>>> >> >>>>>>>>>> {
>>>> >> >>>>>>>>>>   int t1 = x - y;
>>>> >> >>>>>>>>>>   int f2_val = t1 + y;
>>>> >> >>>>>>>>>>   return f2_val;
>>>> >> >>>>>>>>>> }
>>>> >> >>>>>>>>>> scan-tree-dump "gimple_match_and_simplified to f2_val_\\d\+ =
>>>> >> >>>>>>>>>> x_\\d\+\\(D\\)"
>>>> >> >>>>>>>>>> so both f1 and f2's scan-tree-dump have different regexes.
>>>> >> >>>>>>>>>> and f2's regex does not match dump of f1's function.
>>>> >> >>>>>>>>>> This matches all patterns in match-decision-tree.c however this
>>>> >> >>>is not
>>>> >> >>>>>>>>>> ideal,
>>>> >> >>>>>>>>>> since it does not check for matching dump across newlines.
>>>> >> >>>>>>>>>> Could you suggest a better way ?
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> There isn't a good better way (the others explicitely do _not_
>>>> >> >>>match
>>>> >> >>>>>>>>> against
>>>> >> >>>>>>>>> a newline - see the ^ in the \[\] group).  Well, apart from
>>>> >> >>>splitting
>>>> >> >>>>>>>>> the testcase
>>>> >> >>>>>>>>> into multiple files of course.
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>> Richard.
>>>> >> >>>>>>>>>
>>>> >> >>>>>>>>>> Thanks and Regards,
>>>> >> >>>>>>>>>> Prathamesh
>>>> >> >>>>>>>>>>>
>>>> >> >>>>>>>>>>> Thanks,
>>>> >> >>>>>>>>>>> Richard.
>>>> >> >>>>>>>>>>>
>>>> >> >>>>>>>>>>>>> Thanks and Regards,
>>>> >> >>>>>>>>>>>>> Prathamesh
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>> Richard.
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> * Code generation.
>>>> >> >>>>>>>>>>>>>>> Code shall be generated by walking the decision tree.
>>>> >> >>>>>>>>>>>>>>> The way it's constructed, there's no difference between
>>>> >> >>>code
>>>> >> >>>>>>>>>>>>>>> generation
>>>> >> >>>>>>>>>>>>>>> for "matching" and code generation for "transform". For
>>>> >> >>>>>>>>>>>>>>> non-simplificaton
>>>> >> >>>>>>>>>>>>>>> operands, "matching" code is generated, and for
>>>> >> >>>"simplification"
>>>> >> >>>>>>>>>>>>>>> operands,
>>>> >> >>>>>>>>>>>>>>> "transform" code is generated. The tree shall be walked
>>>> >> >>>twice,
>>>> >> >>>>>>>>>>>>>>> once to generate GIMPLE code and second time for GENERIC.
>>>> >> >>>>>>>>>>>>>>> For simplicity, I currently return false whenever there's
>>>> >> >>>a fail
>>>> >> >>>>>>>>>>>>>>> in match,
>>>> >> >>>>>>>>>>>>>>> instead of trying to match the next pattern.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Code-gen for capture - same as capture::gen_gimple_match.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Code-gen for predicate -  I haven't added support for
>>>> >> >>>predicate
>>>> >> >>>>>>>>>>>>>>> in
>>>> >> >>>>>>>>>>>>>>> decision tree yet, but I guess that would be the same as
>>>> >> >>>>>>>>>>>>>>> predicate::gen_gimple_match
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Code-gen for expr.
>>>> >> >>>>>>>>>>>>>>> There are two types of code-gen for expr.
>>>> >> >>>>>>>>>>>>>>> The patch generates following code:
>>>> >> >>>>>>>>>>>>>>> Type 1 - expr is child of root node.
>>>> >> >>>>>>>>>>>>>>> the only code that gets generated is (in
>>>> >> >>>>>>>>>>>>>>> decision_tree::gen_gimple):
>>>> >> >>>>>>>>>>>>>>> if (code == <expr code>)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> tree captures[4] = {}
>>>> >> >>>>>>>>>>>>>>> <generated code for children>
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>> This is similar to generating matching code in
>>>> >> >>>>>>>>>>>>>>> write_nary_simplifiers.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Type 2 - expr_1 is a child of another expr_0 node.
>>>> >> >>>>>>>>>>>>>>> The code gets generated as follows (dt_expr::gen_gimple):
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> gimple def_stmt = SSA_NAME_DEF_STMT (op);
>>>> >> >>>>>>>>>>>>>>> if (is_gimple_assign (def_stmt)
>>>> >> >>>>>>>>>>>>>>>     && gimple_assign_rhs_code (def_stmt) == <expr_1-code>)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> tree op = gimple_assign_rhs1 (def_stmt);
>>>> >> >>>>>>>>>>>>>>> if (valueize && TREE_CODE (op) == SSA_NAME)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>>   op = valueize (op);
>>>> >> >>>>>>>>>>>>>>>   if (!op) return false;
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>> <code-gen for children of expr_1 node>
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Example:
>>>> >> >>>>>>>>>>>>>>> (negate (negate @0))
>>>> >> >>>>>>>>>>>>>>> S1
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> (negate (bit_not @0))
>>>> >> >>>>>>>>>>>>>>> S2
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> decision tree:
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>>                 dummy/root
>>>> >> >>>>>>>>>>>>>>>                         |
>>>> >> >>>>>>>>>>>>>>>            NEGATE_EXPR
>>>> >> >>>>>>>>>>>>>>>              /                  \
>>>> >> >>>>>>>>>>>>>>>      BIT_NOT           NEGATE_EXPR
>>>> >> >>>>>>>>>>>>>>>            |                         |
>>>> >> >>>>>>>>>>>>>>>          @0                     @0
>>>> >> >>>>>>>>>>>>>>>            |                         |
>>>> >> >>>>>>>>>>>>>>>          S1                      S2
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> // code-gen for NEGATE_EXPR (child of root):
>>>> >> >>>>>>>>>>>>>>> if (code == NEGATE_EXPR)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> tree captures[4] = {};
>>>> >> >>>>>>>>>>>>>>> // code gen for BIT_NOT_EXPR
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> gimple def_stmt = SSA_NAME_DEF_STMT (op0);
>>>> >> >>>>>>>>>>>>>>> if (is_gimple_assign (def_stmt)
>>>> >> >>>>>>>>>>>>>>>     && gimple_assign_rhs_code (def_stmt) == BIT_NOT_EXPR)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> tree op = gimple_assign_rhs1 (def_stmt);
>>>> >> >>>>>>>>>>>>>>> if (valueize && TREE_CODE (op) == SSA_NAME)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>>   op = valueize (op);
>>>> >> >>>>>>>>>>>>>>>   if (!op) return false;
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> // code-gen for @0, child of BIT_NOT_EXPR
>>>> >> >>>>>>>>>>>>>>> if (!captures[0])
>>>> >> >>>>>>>>>>>>>>>   captures[0] = op;
>>>> >> >>>>>>>>>>>>>>> else if (captures[0] != op)
>>>> >> >>>>>>>>>>>>>>>   return false;
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> // code-gen for S1, child of @0
>>>> >> >>>>>>>>>>>>>>> < same as code generated by .gen_gimple_transform >
>>>> >> >>>>>>>>>>>>>>> return true;
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>> // code gen for inner NEGATE_EXPR
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> gimple def_stmt = SSA_NAME_DEF_STMT (op0);
>>>> >> >>>>>>>>>>>>>>> if (is_gimple_assign (def_stmt)
>>>> >> >>>>>>>>>>>>>>>     && gimple_assign_rhs_code (def_stmt) == NEGATE_EXPR)
>>>> >> >>>>>>>>>>>>>>> <rest similar to the BIT_NOT case>
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> The following gets duplicated with the patch:
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> gimple_def_stmt = SSA_NAME_DEF_STMT (op0);
>>>> >> >>>>>>>>>>>>>>> if (TREE_CODE (op0) != SSA_NAME)
>>>> >> >>>>>>>>>>>>>>>   return false;
>>>> >> >>>>>>>>>>>>>>> if (is_gimple_assign (def_stmt)
>>>> >> >>>>>>>>>>>>>>>     && gimple_assign_rhs_code (def_stmt) == <expr-code>)
>>>> >> >>>>>>>>>>>>>>> ...
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Improving code-gen for expr:
>>>> >> >>>>>>>>>>>>>>> "gimple def_stmt = ..." and "if (TREE_CODE (op0)" get
>>>> >> >>>duplicated,
>>>> >> >>>>>>>>>>>>>>> while they could be factored out, similar to this:
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>> gimple def_stmt = SSA_NAME_DEF_STMT (op0);
>>>> >> >>>>>>>>>>>>>>> if (TREE_CODE (op0) != SSA_NAME)
>>>> >> >>>>>>>>>>>>>>>   return false;
>>>> >> >>>>>>>>>>>>>>> if (!is_gimple_assign (def_stmt))
>>>> >> >>>>>>>>>>>>>>>   return false;
>>>> >> >>>>>>>>>>>>>>> if (gimple_assign_rhs_code (def_stmt) == BIT_NOT_EXPR)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>>   // code-gen for BIT_NOT_EXPR subtree
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>> else if (gimple_assign_rhs_code (def_stmt) == NEGATE_EXPR)
>>>> >> >>>>>>>>>>>>>>> {
>>>> >> >>>>>>>>>>>>>>>   // code-gen for NEGATE_EXPR subtree
>>>> >> >>>>>>>>>>>>>>> }
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> For factoring "gimple def_stmt ..." and "if (TREE_CODE
>>>> >> >>>(op0) !=
>>>> >> >>>>>>>>>>>>>>> SSA_NAME"
>>>> >> >>>>>>>>>>>>>>> we could have that generated at the parent of expr's node
>>>> >> >>>rather
>>>> >> >>>>>>>>>>>>>>> than
>>>> >> >>>>>>>>>>>>>>> at expr. However that would be incorrect for cases where
>>>> >> >>>not all
>>>> >> >>>>>>>>>>>>>>> children
>>>> >> >>>>>>>>>>>>>>> of a node are expressions:
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Example:
>>>> >> >>>>>>>>>>>>>>> // patterns only for illustration
>>>> >> >>>>>>>>>>>>>>> (negate (bit_not @0))
>>>> >> >>>>>>>>>>>>>>> (negate @0)
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>>                    root
>>>> >> >>>>>>>>>>>>>>>                      |
>>>> >> >>>>>>>>>>>>>>>                   negate
>>>> >> >>>>>>>>>>>>>>>                     /       \
>>>> >> >>>>>>>>>>>>>>>                 bit_not   @0
>>>> >> >>>>>>>>>>>>>>>                     |
>>>> >> >>>>>>>>>>>>>>>                   @0
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> we cannot have the above code generated at negate,
>>>> >> >>>>>>>>>>>>>>> since it's not applicable negate's 2nd child (@0).
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> This can be done by grouping together children that are
>>>> >> >>>>>>>>>>>>>>> expressions.
>>>> >> >>>>>>>>>>>>>>> However the patch does not do that.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> * Code-gen for simplification operand
>>>> >> >>>>>>>>>>>>>>> This involves code-gen for ifexpr and result of pattern.
>>>> >> >>>>>>>>>>>>>>> Calls gen_gimple_transform of ifexpr and result
>>>> >> >>>>>>>>>>>>>>> (dt_simplify::gen_gimple)
>>>> >> >>>>>>>>>>>>>>> So this is really code-gen off AST
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>> Right (modulo replacing captures with their replacements).
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> * Matching multiple patterns
>>>> >> >>>>>>>>>>>>>>> A pattern has following parts: match, ifexpr and result.
>>>> >> >>>>>>>>>>>>>>> If pattern fails in match operand, I guess we can safely
>>>> >> >>>return
>>>> >> >>>>>>>>>>>>>>> false ?
>>>> >> >>>>>>>>>>>>>>> We "club" together patterns that have same match operand,
>>>> >> >>>>>>>>>>>>>>> and use goto, if one of them fails in their
>>>> >> >>>(ifexpr/result) and
>>>> >> >>>>>>>>>>>>>>> then goto the
>>>> >> >>>>>>>>>>>>>>> (ifexpr/result) of the next operand.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Example:
>>>> >> >>>>>>>>>>>>>>> /* x & 0 -> 0 */
>>>> >> >>>>>>>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>>>>>>   (bit_and @0 @1)
>>>> >> >>>>>>>>>>>>>>>   if (INTEGRAL_TYPE_P (TREE_TYPE (@0)) && (@1 ==
>>>> >> >>>>>>>>>>>>>>> integer_zero_node))
>>>> >> >>>>>>>>>>>>>>>   { integer_zero_node; })
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> /* x & -1 -> x */
>>>> >> >>>>>>>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>>>>>>   (bit_and @0 @1)
>>>> >> >>>>>>>>>>>>>>>   if (INTEGRAL_TYPE_P (TREE_TYPE (@0))
>>>> >> >>>>>>>>>>>>>>>      && (@1 == integer_minus_one_node)
>>>> >> >>>>>>>>>>>>>>>   @0)
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> For both patterns match is same.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Decision Tree:
>>>> >> >>>>>>>>>>>>>>>                 bit_and
>>>> >> >>>>>>>>>>>>>>>                 /        \
>>>> >> >>>>>>>>>>>>>>>              @0      @1
>>>> >> >>>>>>>>>>>>>>>                            |
>>>> >> >>>>>>>>>>>>>>>                         S1,  S2
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>> I think it's worth adding a diagnostic to genmach whenever
>>>> >> >>>exactly
>>>> >> >>>>>>>>>>>>>> same matches appear.  But I'd say generally we'd support
>>>> >> >>>this
>>>> >> >>>>>>>>>>>>>> by testing the ifexpr of the next pattern.
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> S1 represents <ifexpr, result> of pattern-1, and S2
>>>> >> >>>represents
>>>> >> >>>>>>>>>>>>>>> <ifexpr, result>
>>>> >> >>>>>>>>>>>>>>> of pattern-2 respectively.
>>>> >> >>>>>>>>>>>>>>> S1, S2 would be stored as children of @1 (the last operand
>>>> >> >>>of
>>>> >> >>>>>>>>>>>>>>> n-ary operator),
>>>> >> >>>>>>>>>>>>>>> in dt_operand::kids vector.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> The code would be generated as:
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> matching code.
>>>> >> >>>>>>>>>>>>>>> if (! pattern-1 ifexpr condition)
>>>> >> >>>>>>>>>>>>>>>   goto simplify2;  // next pattern with the same "match"
>>>> >> >>>operand.
>>>> >> >>>>>>>>>>>>>>> transform code for pattern 1
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> simplify2:
>>>> >> >>>>>>>>>>>>>>> if (! pattern-2 ifexpr condition)
>>>> >> >>>>>>>>>>>>>>>   return false;  // last pattern
>>>> >> >>>>>>>>>>>>>>> transform code for pattern 2.
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> If matching itself fails, that is neither of the decisions
>>>> >> >>>get
>>>> >> >>>>>>>>>>>>>>> matched,
>>>> >> >>>>>>>>>>>>>>> I believe we can then return false as it cannot match any
>>>> >> >>>other
>>>> >> >>>>>>>>>>>>>>> pattern ?
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> * patterns needing hacks like cond_expr or GENERIC support
>>>> >> >>>>>>>>>>>>>>> I haven't given thought to this yet. I suppose we can look
>>>> >> >>>to
>>>> >> >>>>>>>>>>>>>>> handle
>>>> >> >>>>>>>>>>>>>>> these after adding support for GENERIC. Instead of
>>>> >> >>>generating
>>>> >> >>>>>>>>>>>>>>> GENERIC
>>>> >> >>>>>>>>>>>>>>> matching in
>>>> >> >>>>>>>>>>>>>>> gimple_match_and_simplify, could we then call
>>>> >> >>>>>>>>>>>>>>> generic_match_and_simplify from
>>>> >> >>>>>>>>>>>>>>> within gimple_match_and_simplify ?
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>> Yes (that's what's currently done btw).
>>>> >> >>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> * Tests
>>>> >> >>>>>>>>>>>>>>> The patch transformed the following patterns:
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>>>>>>   (negate (bit_not @0))
>>>> >> >>>>>>>>>>>>>>>   if (INTEGRAL_TYPE_P (TREE_TYPE (@0)))
>>>> >> >>>>>>>>>>>>>>>   (plus @0 { build_int_cst (TREE_TYPE (@0)), 1); }))
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> (match_and_simplify
>>>> >> >>>>>>>>>>>>>>>   (negate (negate @0))
>>>> >> >>>>>>>>>>>>>>>   @0)
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> I have attached test-case I tried it with (negate.c)
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> * Conclusion
>>>> >> >>>>>>>>>>>>>>> Does it sound reasonable ? I am going to be re-writing the
>>>> >> >>>>>>>>>>>>>>> decision tree from scratch, but is the basic idea fine ?
>>>> >> >>>Or should
>>>> >> >>>>>>>>>>>>>>> we
>>>> >> >>>>>>>>>>>>>>> take a different approach ?
>>>> >> >>>>>>>>>>>>>>>
>>>> >> >>>>>>>>>>>>>>> Thanks and Regards,
>>>> >> >>>>>>>>>>>>>>> Prathamesh
>>>> >> >>>>>>
>>>> >> >>
>>>> >> >>

Index: gcc/genmatch.c
===================================================================
--- gcc/genmatch.c	(revision 211732)
+++ gcc/genmatch.c	(working copy)
@@ -29,7 +29,8 @@ along with GCC; see the file COPYING3.
 #include "hashtab.h"
 #include "hash-table.h"
 #include "vec.h"
-
+#include <stdlib.h>
+#include <limits.h>
 
 /* libccp helpers.  */
 
@@ -559,6 +560,648 @@ capture::gen_gimple_match (FILE *f, cons
 }
 
 
+
+bool
+cmp_operand (operand *o1, operand *o2)
+{
+  if (!o1 || !o2 || o1->type != o2->type)
+    return false;
+
+  if (o1->type == operand::OP_PREDICATE)
+    {
+      predicate *p1 = static_cast<predicate *>(o1);
+      predicate *p2 = static_cast<predicate *>(o2);
+      return strcmp (p1->ident, p2->ident) == 0;
+    }
+  else if (o1->type == operand::OP_EXPR)
+    {
+      expr *e1 = static_cast<expr *>(o1);
+      expr *e2 = static_cast<expr *>(o2);
+      return strcmp (e1->operation->op->id, e2->operation->op->id) == 0;
+    }
+  else
+    return false;
+}
+
+void
+print_flattened_operand (operand *o, FILE *f = stderr)
+{
+  if (o->type == operand::OP_CAPTURE)
+    fprintf (f, "@%s", (static_cast<capture *>(o))->where);
+  else if (o->type == operand::OP_PREDICATE)
+    fprintf (f, "%s", (static_cast<predicate *>(o))->ident);
+  else if (o->type == operand::OP_EXPR)
+    {
+      expr *e = static_cast <expr *>(o);
+      fprintf (f, "%s", e->operation->op->id);
+    }
+  else if (o->type == operand::OP_C_EXPR)
+    fprintf (f, "c_expr");
+  else
+    gcc_unreachable ();
+}
+
+struct dt_node
+{
+  enum dt_type { DT_NODE, DT_OPERAND, DT_TRUE, DT_MATCH, DT_SIMPLIFY };
+
+  enum dt_type type;
+  unsigned level;
+  vec<dt_node *> kids;
+
+  dt_node (enum dt_type type_): type (type_), level (0), kids (vNULL) {} 
+  
+  dt_node *append_node (dt_node *); 
+  dt_node *append_op (operand *, dt_node *parent = 0, unsigned pos = 0); 
+  dt_node *append_true_op (dt_node *parent = 0, unsigned pos = 0);
+  dt_node *append_match_op (unsigned, dt_node *parent = 0, unsigned pos = 0);
+  dt_node *append_simplify (operand *, operand *, unsigned, unsigned *); 
+
+  virtual void gen_gimple (FILE *) {}
+};
+
+struct dt_operand: public dt_node
+{
+  operand *op;
+  unsigned m_level; // for match
+  dt_operand *parent;
+  unsigned pos;
+  vec<unsigned> temps;
+  static unsigned temp_count;
+ 
+  dt_operand (enum dt_type type, operand *op_, unsigned m_level_, dt_operand *parent_ = 0, unsigned pos_ = 0)
+	: dt_node (type), op (op_), m_level (m_level_), parent (parent_), pos (pos_), temps (vNULL) {}
+
+  virtual void gen_gimple (FILE *);
+  unsigned gen_gimple_predicate (FILE *, const char *);
+  unsigned gen_gimple_match_op (FILE *, const char *);
+
+  unsigned gen_gimple_expr (FILE *, const char *);
+  void gen_gimple_expr_expr (FILE *, expr *);
+  void gen_gimple_expr_fn (FILE *, expr *);
+
+  unsigned gen_generic_expr (FILE *, const char *);
+  void gen_generic_expr_expr (FILE *, expr *, const char *);
+  void gen_generic_expr_fn (FILE *, expr *, const char *);
+};
+
+unsigned dt_operand::temp_count = 0;
+
+struct dt_simplify: public dt_node
+{
+  static const unsigned level_max = UINT_MAX;
+  static const unsigned capture_max = 4;
+  operand *ifexpr;
+  operand *result;
+  unsigned pattern_no;
+  unsigned indexes[capture_max]; 
+  
+  dt_simplify (operand *ifexpr_, operand *result_, unsigned pattern_no_, unsigned *indexes_)
+	: dt_node (DT_SIMPLIFY), ifexpr (ifexpr_), result (result_), pattern_no (pattern_no_)
+  {
+    for (unsigned i = 0; i < capture_max; ++i)
+      indexes[i] = indexes_[i];
+  }
+
+  virtual void gen_gimple (FILE *f);
+};
+
+struct decision_tree
+{
+  dt_node *root;
+  
+  void insert (struct simplify *, unsigned);
+  void gen_gimple (FILE *f = stderr);
+  void print (FILE *f = stderr);
+
+  decision_tree () { root = new dt_node (dt_node::DT_NODE); }
+
+  static dt_node *insert_operand (dt_node *, operand *, unsigned *indexes, unsigned pos = 0, dt_node *parent = 0);
+  static dt_node *find_node (vec<dt_node *>&, dt_node *);
+  static bool cmp_node (dt_node *, dt_node *);
+  static void print_node (dt_node *, FILE *f = stderr, unsigned = 0);
+};
+
+bool
+decision_tree::cmp_node (dt_node *n1, dt_node *n2)
+{
+  if (!n1 || !n2 || n1->type != n2->type)
+    return false;
+
+  if (n1 == n2 || n1->type == dt_node::DT_TRUE)
+    return true;
+
+  if (n1->type == dt_node::DT_OPERAND)
+    return cmp_operand ((static_cast<dt_operand *> (n1))->op, (static_cast<dt_operand *> (n2))->op);
+
+  else if (n1->type == dt_node::DT_MATCH)
+    return (static_cast<dt_operand *> (n1))->m_level == (static_cast<dt_operand *> (n2))->m_level;
+
+  else
+    return false;
+}
+
+dt_node *
+decision_tree::find_node (vec<dt_node *>& ops, dt_node *p)
+{
+  for (unsigned i = 0; i < ops.length (); ++i)
+    if (decision_tree::cmp_node (ops[i], p))
+      return ops[i]; 
+  
+  return 0;
+}
+
+dt_node *
+dt_node::append_node (dt_node *n)
+{
+  dt_node *kid;
+
+  kid = decision_tree::find_node (kids, n);
+  if (kid)
+    return kid;
+
+  kids.safe_push (n);
+  n->level = this->level + 1;
+
+  unsigned len = kids.length ();
+
+  if (len > 1 && kids[len - 2]->type == dt_node::DT_TRUE)
+    {
+      dt_node *p = kids[len - 2];
+      kids[len - 2] = kids[len - 1];
+      kids[len - 1] = p;
+    }
+
+  return n;
+}
+
+dt_node *
+dt_node::append_op (operand *op, dt_node *parent, unsigned pos)
+{
+  dt_operand *parent_ = static_cast<dt_operand *> (parent);
+  dt_node *n = new dt_operand (DT_OPERAND, op, 0, parent_, pos);
+  dt_node *p = append_node (n);
+
+  if (p != n)
+    free (n);
+
+  return p; 
+}
+
+dt_node *
+dt_node::append_true_op (dt_node *parent, unsigned pos)
+{
+  dt_operand *parent_ = static_cast<dt_operand *> (parent);
+  dt_node *n = new dt_operand (DT_TRUE, 0, 0, parent_, pos);
+  dt_node *p = append_node (n);
+
+  if (p != n)
+    free (n);
+
+  return p;
+}
+
+dt_node *
+dt_node::append_match_op (unsigned m_level, dt_node *parent, unsigned pos)
+{
+  dt_operand *parent_ = static_cast<dt_operand *> (parent);
+  dt_node *n = new dt_operand (DT_MATCH, 0, m_level, parent_, pos);
+  dt_node *p = append_node (n);
+
+  if (p != n)
+    free (n);
+
+  return p;
+}
+
+dt_node *
+dt_node::append_simplify (operand *ifexpr, operand *result, unsigned pattern_no, unsigned *indexes) 
+{
+  dt_node *n = new dt_simplify (ifexpr, result, pattern_no, indexes);
+  return append_node (n);
+}
+
+dt_node *
+decision_tree::insert_operand (dt_node *p, operand *o, unsigned *indexes, unsigned pos, dt_node *parent) 
+{
+  dt_node *q;
+
+  if (o->type == operand::OP_CAPTURE)
+    {
+      capture *c = static_cast<capture *> (o);
+      unsigned capt_index = atoi (c->where);
+
+      if (indexes[capt_index] == dt_simplify::level_max)
+	{
+	  indexes[capt_index] = p->level + 1;
+
+	  if (c->what)
+	    return insert_operand (p, c->what, indexes, pos, parent);
+	  else
+	    {
+	      p = p->append_true_op (parent, pos);
+	      return p;
+	    }
+	}
+      else
+	{
+	  p = p->append_match_op (indexes[capt_index], parent, pos);
+	  if (c->what)
+	    return insert_operand (p, c->what, indexes, 0, p);
+	  else
+	    return p;
+	}
+    }
+  p = p->append_op (o, parent, pos);
+  q = p;
+
+  if (o->type == operand::OP_EXPR)
+    {
+      expr *e = static_cast<expr *> (o);
+      for (unsigned i = 0; i < e->ops.length (); ++i)
+	q = decision_tree::insert_operand (q, e->ops[i], indexes, i, p);		
+    }
+
+  return q;
+}
+
+
+void
+decision_tree::insert (struct simplify *s, unsigned pattern_no)
+{
+  if (s->match->type != operand::OP_EXPR)
+    return;
+
+  unsigned indexes[dt_simplify::capture_max];
+
+  for (unsigned i = 0; i < dt_simplify::capture_max; ++i)
+    indexes[i] = dt_simplify::level_max;
+
+  dt_node *p = decision_tree::insert_operand (root, s->match, indexes); 
+  p->append_simplify (s->ifexpr, s->result, pattern_no, indexes);
+}
+
+void
+decision_tree::print_node (dt_node *p, FILE *f, unsigned indent)
+{
+  if (p->type == dt_node::DT_NODE)
+    fprintf (f, "root");
+  else
+    {
+      fprintf (f, "|");
+      for (unsigned i = 0; i < indent; i++)
+	fprintf (f, "-");
+
+      if (p->type == dt_node::DT_OPERAND)
+	{
+	  dt_operand *dop = static_cast<dt_operand *>(p);
+	  print_flattened_operand (dop->op, f);
+	} 
+      else if (p->type == dt_node::DT_TRUE)
+	fprintf (f, "true");
+      else if (p->type == dt_node::DT_MATCH)
+	fprintf (f, "match (%u)", ((static_cast<dt_operand *>(p))->m_level));
+      else if (p->type == dt_node::DT_SIMPLIFY)
+	{
+	  dt_simplify *s = static_cast<dt_simplify *> (p);
+	  fprintf (f, "simplify_%u { ", s->pattern_no); 
+	  for (unsigned i = 0; i < dt_simplify::capture_max; ++i)
+	    fprintf (f, "%u, ", s->indexes[i]);
+	  fprintf (f, " } "); 
+	}
+    }      
+
+  fprintf (stderr, " (%p), %u, %u\n", (void *) p, p->level, p->kids.length ());
+
+  for (unsigned i = 0; i < p->kids.length (); ++i)
+    decision_tree::print_node (p->kids[i], f, indent + 2);
+}
+
+
+void
+decision_tree::print (FILE *f)
+{
+  return decision_tree::print_node (root, f);
+}
+
+void
+write_fn_prototype (FILE *f, unsigned n)
+{
+  fprintf (f, "static bool\n"
+          "gimple_match_and_simplify (code_helper code, tree type");
+  for (unsigned i = 0; i < n; ++i)
+    fprintf (f, ", tree op%d", i);
+  fprintf (f, ", code_helper *res_code, tree *res_ops, gimple_seq *seq, tree (*valueize)(tree))\n");
+}
+
+unsigned
+dt_operand::gen_gimple_predicate (FILE *f, const char *opname)
+{
+  predicate *p = static_cast<predicate *> (op);
+
+  fprintf (f, "if (%s (%s))\n", p->ident, opname);
+  fprintf (f, "{\n");
+  return 1;
+}
+
+unsigned
+dt_operand::gen_gimple_match_op (FILE *f, const char *opname)
+{
+  fprintf (f, "if (%s == o%u)\n", opname, m_level);
+  fprintf (f, "{\n");
+  return 1;
+}
+
+void
+dt_operand::gen_gimple_expr_fn (FILE *f, expr *e)
+{
+  unsigned n_ops = e->ops.length ();
+
+  fn_id *op = static_cast <fn_id *> (e->operation->op);
+  fprintf (f, "if (gimple_call_builtin_p (def_stmt, %s))\n", op->id);
+  fprintf (f, "{\n");
+
+  for (unsigned i = 0; i < n_ops; ++i)
+    {
+      char child_opname[20];
+      sprintf (child_opname, "t%u", temps[i]);
+      fprintf (f, "%s = gimple_call_arg (def_stmt, %u);\n", child_opname, i);
+      fprintf (f, "if (do_valueize (valueize, %s))\n", child_opname);
+      fprintf (f, "{\n");
+    } 
+}
+
+void
+dt_operand::gen_gimple_expr_expr (FILE *f, expr *e)
+{
+  unsigned n_ops = e->ops.length (); 
+
+  operator_id *op_id = static_cast <operator_id *> (e->operation->op);
+  
+  if (op_id->code == NOP_EXPR || op_id->code == CONVERT_EXPR)
+    fprintf (f, "if (is_gimple_assign (def_stmt) &&\n"
+                "   (gimple_assign_rhs_code (def_stmt) == %s\n"
+	        "   || CONVERT_EXPR_CODE_P (gimple_assign_rhs_code (def_stmt))))\n", op_id->id);
+  else
+    fprintf (f, "if (is_gimple_assign (def_stmt) && gimple_assign_rhs_code (def_stmt) == %s)\n", op_id->id);
+
+  fprintf (f, "{\n");
+  
+  for (unsigned i = 0; i < n_ops; ++i)
+    {
+      char child_opname[20];
+      sprintf (child_opname, "t%u", temps[i]);
+      fprintf (f, "%s = gimple_assign_rhs%u (def_stmt);\n", child_opname, i + 1);
+      fprintf (f, "if (do_valueize (valueize, %s))\n", child_opname);
+      fprintf (f, "{\n");
+    }      
+} 
+
+unsigned
+dt_operand::gen_gimple_expr (FILE *f, const char *opname)
+{
+  unsigned i;
+  expr *e = static_cast<expr *> (op);
+
+  for (i = 0; i < e->ops.length (); ++i)
+    {
+      fprintf (f, "tree t%u = NULL_TREE;\n", dt_operand::temp_count);
+      temps.safe_push (temp_count);
+      temp_count++;
+    }
+
+  fprintf (f, "if (TREE_CODE (%s) == SSA_NAME)\n", opname);
+  fprintf (f, "{\n");
+  
+  fprintf (f, "gimple def_stmt = SSA_NAME_DEF_STMT (%s);\n", opname);
+  (e->operation->op->kind == id_base::CODE) ? gen_gimple_expr_expr (f, e) : gen_gimple_expr_fn (f, e);
+
+  return e->ops.length () + 2;
+}
+
+void
+dt_operand::gen_generic_expr_expr (FILE *f, expr *e, const char *opname)
+{
+  unsigned n_ops = e->ops.length ();
+
+  fprintf (f, "if (TREE_CODE (%s) == %s)\n", opname, e->operation->op->id);
+  fprintf (f, "{\n");
+
+  for (unsigned i = 0; i < n_ops; ++i)
+    {
+      char child_opname[20];
+      sprintf (child_opname, "t%u", temps[i]);
+      fprintf (f, "%s = TREE_OPERAND (%s, %u);\n", child_opname, opname, i);
+      fprintf (f, "if (do_valueize (valueize, %s))\n", child_opname);
+      fprintf (f, "{\n");
+    }
+}   
+
+void
+dt_operand::gen_generic_expr_fn (FILE *f, expr *e, const char *opname)
+{
+  unsigned n_ops = e->ops.length ();
+  fn_id *op = static_cast <fn_id *> (e->operation->op);
+
+  fprintf (f, "if (TREE_CODE (%s) == CALL_EXPR\n"
+               "    && TREE_CODE (CALL_EXPR_FN (%s)) == ADDR_EXPR\n"
+               "    && TREE_CODE (TREE_OPERAND (CALL_EXPR_FN (%s), 0)) == FUNCTION_DECL\n"
+               "    && DECL_BUILT_IN_CLASS (TREE_OPERAND (CALL_EXPR_FN (%s), 0)) == BUILT_IN_NORMAL\n"
+               "    && DECL_FUNCTION_CODE (TREE_OPERAND (CALL_EXPR_FN (%s), 0)) == %s)\n",
+               opname, opname, opname, opname, opname, op->id);
+  fprintf (f, "  {\n");
+
+  for (unsigned i = 0; i < n_ops; ++i)
+    {
+      char child_opname[20];
+      sprintf (child_opname, "t%u", temps[i]);
+      fprintf (f, "%s = CALL_EXPR_ARG (%s, %u);\n", child_opname, opname, i);
+      fprintf (f, "if (do_valueize (valueize, %s))\n", child_opname);
+      fprintf (f, "{\n");
+    }
+}
+
+unsigned
+dt_operand::gen_generic_expr (FILE *f, const char *opname)
+{
+  unsigned i;
+  expr *e = static_cast<expr *> (op);
+
+  for (i = 0; i < e->ops.length (); ++i)
+    {
+      fprintf (f, "tree t%u = NULL_TREE;\n", dt_operand::temp_count);
+      temps.safe_push (temp_count);
+      temp_count++;
+    }
+
+  gen_generic_expr_expr (f, e, opname);
+  return e->ops.length () + 1;
+}
+
+void
+dt_operand::gen_gimple (FILE *f)
+{
+  char opname[20];
+  sprintf (opname, "o%u", level);
+  
+
+  fprintf (f, "{\n");
+
+  fprintf (stderr, "pos = %u\n", pos);
+
+  if (parent->parent == 0)
+    fprintf (f, "tree %s = op%u;\n", opname, pos);
+  else if (parent->type == dt_node::DT_MATCH)
+    fprintf (f, "tree %s = o%u;\n", opname, parent->level);
+  else if (parent->type == dt_node::DT_OPERAND && parent->op->type == operand::OP_EXPR) 
+    fprintf (f, "tree %s = t%u;\n", opname, parent->temps[pos]);
+  else
+    gcc_unreachable ();
+
+  unsigned n_braces = 0;
+ 
+  if (type == DT_OPERAND)
+    switch (op->type)
+      {
+	case operand::OP_PREDICATE:
+	  n_braces = gen_gimple_predicate (f, opname);
+	  break;
+
+	case operand::OP_EXPR:
+	{
+	  expr *e = static_cast<expr *> (op);
+  	  operator_id *op_id = static_cast <operator_id *> (e->operation->op);
+	  enum tree_code code = op_id->code;
+
+	  if (code == REALPART_EXPR || code == IMAGPART_EXPR || code == VIEW_CONVERT_EXPR || code == BIT_FIELD_REF)
+	    n_braces = gen_generic_expr (f, opname);
+
+	  // check for cond_expr, 0th operand -> generic
+	  else if (parent->type == dt_node::DT_OPERAND && parent->op->type == operand::OP_EXPR)
+	    {
+	      e = static_cast<expr *> (parent->op);
+	      op_id = static_cast <operator_id *> (e->operation->op);
+	      n_braces = (op_id->code == COND_EXPR && pos == 0) ? gen_generic_expr (f, opname) : gen_gimple_expr (f, opname);
+	    }
+	  else
+	    n_braces = gen_gimple_expr (f, opname);
+	}
+	  break;
+
+	default:
+	  gcc_unreachable ();
+      }
+  else if (type == DT_TRUE)
+    ;
+  else if (type == DT_MATCH)
+    n_braces = gen_gimple_match_op (f, opname);
+  else
+    gcc_unreachable ();
+
+  unsigned i;
+
+  for (i = 0; i < kids.length (); ++i)
+    kids[i]->gen_gimple (f);
+
+  for (i = 0; i < n_braces; ++i)
+    fprintf (f, "}\n");
+  
+  fprintf (f, "}\n");
+}
+
+void
+dt_simplify::gen_gimple (FILE *f)
+{
+  dt_simplify *s = this;
+
+  char *fail_label = 0;
+
+  fprintf (f, "/* simplify %u */\n", pattern_no);
+
+  fprintf (f, "{\n");
+  fprintf (f, "tree captures[4] = {};\n");
+
+  for (unsigned i = 0; i < dt_simplify::capture_max; ++i)
+    if (indexes[i] != dt_simplify::level_max) 
+      fprintf (f, "captures[%u] = o%u;\n", i, indexes[i]); 
+
+  if (s->ifexpr)
+	{
+//	  output_line_directive (f, s->ifexpr_location);
+	  fprintf (f, "if (");
+	  s->ifexpr->gen_gimple_transform (f, fail_label, NULL);
+	  fprintf (f, ")\n");
+	  fprintf (f, "{\n");
+	}
+//      output_line_directive (f, s->result_location);
+
+      if (s->result->type == operand::OP_EXPR)
+	{
+	  expr *e = static_cast <expr *> (s->result);
+	  fprintf (f, "*res_code = %s;\n", e->operation->op->id);
+	  for (unsigned j = 0; j < e->ops.length (); ++j)
+	    {
+	      char dest[32];
+	      snprintf (dest, 32, "  res_ops[%d]", j);
+	      e->ops[j]->gen_gimple_transform (f, fail_label, dest);
+	    }
+	  /* Re-fold the toplevel result.  It's basically an embedded
+	     gimple_build w/o actually building the stmt.  */
+	  fprintf (f, "gimple_resimplify%d (seq, res_code, type, "
+		   "res_ops, valueize);\n", e->ops.length ());
+	}
+      else if (s->result->type == operand::OP_CAPTURE
+	       || s->result->type == operand::OP_C_EXPR)
+	{
+	  s->result->gen_gimple_transform (f, fail_label,
+					   "res_ops[0]");
+	  fprintf (f, "*res_code = TREE_CODE (res_ops[0]);\n");
+	}
+      else
+	gcc_unreachable ();
+
+      fprintf (f, "return true;\n");
+      if (s->ifexpr)
+	fprintf (f, "}\n");
+
+  fprintf (f, "}\n");
+}
+
+
+
+void
+decision_tree::gen_gimple (FILE *f)
+{
+  write_fn_prototype (f, 1);
+  fprintf (f, "{ return gimple_match_and_simplify (code, type, op0, NULL_TREE, NULL_TREE, res_code, res_ops, seq, valueize); }\n\n");
+
+  write_fn_prototype (f, 2);
+  fprintf (f, "{ return gimple_match_and_simplify (code, type, op0, op1, NULL_TREE, res_code, res_ops, seq, valueize); }\n\n");
+
+  write_fn_prototype (f, 3);
+  fprintf (f, "{\n");
+
+  for (unsigned i = 0; i < root->kids.length (); i++)
+    {
+      dt_operand *dop = static_cast<dt_operand *>(root->kids[i]);
+      expr *e = static_cast<expr *>(dop->op);
+
+      if (i)
+        fprintf (f, "else ");
+      fprintf (f, "if (code == %s)\n", e->operation->op->id);
+      fprintf (f, "{\n");
+
+      for (unsigned j = 0; j < dop->kids.length (); ++j)
+	dop->kids[j]->gen_gimple (f);
+
+      fprintf (f, "}\n");
+    }
+
+  fprintf (f, "return false;\n");
+  fprintf (f, "}\n");
+}
+
+
 static void
 write_nary_simplifiers (FILE *f, vec<simplify *>& simplifiers, unsigned n)
 {
@@ -713,9 +1356,11 @@ write_gimple (FILE *f, vec<simplify *>&
   for (unsigned i = 0; i < simplifiers.length (); ++i)
     outline_c_exprs (stdout, simplifiers[i]->result);
 
+#if 0
   write_nary_simplifiers (f, simplifiers, 1);
   write_nary_simplifiers (f, simplifiers, 2);
   write_nary_simplifiers (f, simplifiers, 3);
+#endif
 }
 
 
@@ -1043,7 +1688,14 @@ main(int argc, char **argv)
     }
   while (1);
 
+  decision_tree dt;
+  for (unsigned i = 0; i < simplifiers.length (); ++i)
+    dt.insert (simplifiers[i], i);
+
+  dt.print (stderr);
+ 
   write_gimple (stdout, simplifiers);
+  dt.gen_gimple (stdout);
 
   cpp_finish (r, NULL);
   cpp_destroy (r);
Index: gcc/gimple-match-head.c
===================================================================
--- gcc/gimple-match-head.c	(revision 211732)
+++ gcc/gimple-match-head.c	(working copy)
@@ -706,3 +706,10 @@ gimple_match_and_simplify (gimple_stmt_i
   return true;
 }
 
+static tree 
+do_valueize (tree (*valueize)(tree), tree op)
+{
+  if (valueize && TREE_CODE (op) == SSA_NAME)
+    return valueize (op);
+  return op;
+}