RE: [PATCH 6/8 v9]middle-end slp: support complex FMA and complex FMA conjugate

[Tamar Christina <Tamar.Christina@arm.com>]

Hi Richi,

> -----Original Message-----
> From: Richard Biener <rguenther@suse.de>
> Sent: Friday, January 8, 2021 9:45 AM
> To: Tamar Christina <Tamar.Christina@arm.com>
> Cc: gcc-patches@gcc.gnu.org; nd <nd@arm.com>; ook@ucw.cz
> Subject: Re: [PATCH 6/8 v9]middle-end slp: support complex FMA and
> complex FMA conjugate
> 
> On Mon, 28 Dec 2020, Tamar Christina wrote:
> 
> > Hi All,
> >
> > This adds support for FMA and FMA conjugated to the slp pattern matcher.
> >
> > Bootstrapped Regtested on aarch64-none-linux-gnu, x86_64-pc-linux-gnu
> > and no issues.
> >
> > Ok for master?
> >
> > Thanks,
> > Tamar
> >
> > gcc/ChangeLog:
> >
> > 	* internal-fn.def (COMPLEX_FMA, COMPLEX_FMA_CONJ): New.
> > 	* optabs.def (cmla_optab, cmla_conj_optab): New.
> > 	* doc/md.texi: Document them.
> > 	* tree-vect-slp-patterns.c (vect_match_call_p,
> > 	class complex_fma_pattern, vect_slp_reset_pattern,
> > 	complex_fma_pattern::matches, complex_fma_pattern::recognize,
> > 	complex_fma_pattern::build): New.
> >
> > --- inline copy of patch --
> > diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi index
> >
> b8cc90e1a75e402abbf8a8cf2efefc1a333f8b3a..6d5a98c4946d3ff4c2b8abea5c2
> 9
> > caa6863fd3f7 100644
> > --- a/gcc/doc/md.texi
> > +++ b/gcc/doc/md.texi
> > @@ -6202,6 +6202,51 @@ The operation is only supported for vector
> modes @var{m}.
> >
> >  This pattern is not allowed to @code{FAIL}.
> >
> > +@cindex @code{cmla@var{m}4} instruction pattern @item
> > +@samp{cmla@var{m}4} Perform a vector multiply and accumulate that is
> > +semantically the same as a multiply and accumulate of complex
> > +numbers.
> > +
> > +@smallexample
> > +  complex TYPE c[N];
> > +  complex TYPE a[N];
> > +  complex TYPE b[N];
> > +  for (int i = 0; i < N; i += 1)
> > +    @{
> > +      c[i] += a[i] * b[i];
> > +    @}
> > +@end smallexample
> > +
> > +In GCC lane ordering the real part of the number must be in the even
> > +lanes with the imaginary part in the odd lanes.
> > +
> > +The operation is only supported for vector modes @var{m}.
> > +
> > +This pattern is not allowed to @code{FAIL}.
> > +
> > +@cindex @code{cmla_conj@var{m}4} instruction pattern @item
> > +@samp{cmla_conj@var{m}4} Perform a vector multiply by conjugate and
> > +accumulate that is semantically the same as a multiply and accumulate
> > +of complex numbers where the second multiply arguments is conjugated.
> > +
> > +@smallexample
> > +  complex TYPE c[N];
> > +  complex TYPE a[N];
> > +  complex TYPE b[N];
> > +  for (int i = 0; i < N; i += 1)
> > +    @{
> > +      c[i] += a[i] * conj (b[i]);
> > +    @}
> > +@end smallexample
> > +
> > +In GCC lane ordering the real part of the number must be in the even
> > +lanes with the imaginary part in the odd lanes.
> > +
> > +The operation is only supported for vector modes @var{m}.
> > +
> > +This pattern is not allowed to @code{FAIL}.
> > +
> >  @cindex @code{cmul@var{m}4} instruction pattern  @item
> > @samp{cmul@var{m}4}  Perform a vector multiply that is semantically
> > the same as multiply of diff --git a/gcc/internal-fn.def
> > b/gcc/internal-fn.def index
> >
> 5a0bbe3fe5dee591d54130e60f6996b28164ae38..305450e026d4b94ab62ceb9c
> a719
> > ec5570ff43eb 100644
> > --- a/gcc/internal-fn.def
> > +++ b/gcc/internal-fn.def
> > @@ -288,6 +288,8 @@ DEF_INTERNAL_FLT_FN (LDEXP, ECF_CONST, ldexp,
> > binary)
> >
> >  /* Ternary math functions.  */
> >  DEF_INTERNAL_FLT_FLOATN_FN (FMA, ECF_CONST, fma, ternary)
> > +DEF_INTERNAL_OPTAB_FN (COMPLEX_FMA, ECF_CONST, cmla, ternary)
> > +DEF_INTERNAL_OPTAB_FN (COMPLEX_FMA_CONJ, ECF_CONST,
> cmla_conj,
> > +ternary)
> >
> >  /* Unary integer ops.  */
> >  DEF_INTERNAL_INT_FN (CLRSB, ECF_CONST | ECF_NOTHROW, clrsb,
> unary)
> > diff --git a/gcc/optabs.def b/gcc/optabs.def index
> >
> e82396bae1117c6de91304761a560b7fbcb69ce1..8e2758d685ed85e02df10dac
> 571e
> > b40d45a294ed 100644
> > --- a/gcc/optabs.def
> > +++ b/gcc/optabs.def
> > @@ -294,6 +294,8 @@ OPTAB_D (cadd90_optab, "cadd90$a3")  OPTAB_D
> > (cadd270_optab, "cadd270$a3")  OPTAB_D (cmul_optab, "cmul$a3")
> > OPTAB_D (cmul_conj_optab, "cmul_conj$a3")
> > +OPTAB_D (cmla_optab, "cmla$a4")
> > +OPTAB_D (cmla_conj_optab, "cmla_conj$a4")
> >  OPTAB_D (cos_optab, "cos$a2")
> >  OPTAB_D (cosh_optab, "cosh$a2")
> >  OPTAB_D (exp10_optab, "exp10$a2")
> > diff --git a/gcc/tree-vect-slp-patterns.c
> > b/gcc/tree-vect-slp-patterns.c index
> >
> 82721acbab8cf81c4d6f9954c98fb913a7bb6282..3625a80c08e3d70fd362fc52e1
> 7e
> > 65b3b2c7da83 100644
> > --- a/gcc/tree-vect-slp-patterns.c
> > +++ b/gcc/tree-vect-slp-patterns.c
> > @@ -325,6 +325,24 @@ vect_match_expression_p (slp_tree node,
> tree_code code)
> >    return true;
> >  }
> >
> > +/* Checks to see if the expression represented by NODE is a call to the
> internal
> > +   function FN.  */
> > +
> > +static inline bool
> > +vect_match_call_p (slp_tree node, internal_fn fn) {
> > +  if (!node
> > +      || !SLP_TREE_REPRESENTATIVE (node))
> > +    return false;
> > +
> > +  gimple* expr = STMT_VINFO_STMT (SLP_TREE_REPRESENTATIVE
> (node));
> > + if (!expr
> > +      || !gimple_call_internal_p (expr, fn))
> > +    return false;
> > +
> > +   return true;
> > +}
> > +
> >  /* Check if the given lane permute in PERMUTES matches an alternating
> sequence
> >     of {even odd even odd ...}.  This to account for unrolled loops.  Further
> >     mode there resulting permute must be linear.   */
> > @@ -1081,6 +1099,161 @@ complex_mul_pattern::build (vec_info *vinfo)
> >    complex_pattern::build (vinfo);
> >  }
> >
> >
> +/*********************************************************
> ***********
> > +***********
> > + * complex_fma_pattern class
> > +
> >
> +*********************************************************
> ************
> > +*********/
> > +
> > +class complex_fma_pattern : public complex_pattern {
> > +  protected:
> > +    complex_fma_pattern (slp_tree *node, vec<slp_tree> *m_ops,
> internal_fn ifn)
> > +      : complex_pattern (node, m_ops, ifn)
> > +    {
> > +      this->m_num_args = 3;
> > +    }
> > +
> > +  public:
> > +    void build (vec_info *);
> > +    static internal_fn
> > +    matches (complex_operation_t op, slp_tree_to_load_perm_map_t *,
> slp_tree *,
> > +	     vec<slp_tree> *);
> > +
> > +    static vect_pattern*
> > +    recognize (slp_tree_to_load_perm_map_t *, slp_tree *);
> > +
> > +    static vect_pattern*
> > +    mkInstance (slp_tree *node, vec<slp_tree> *m_ops, internal_fn ifn)
> > +    {
> > +      return new complex_fma_pattern (node, m_ops, ifn);
> > +    }
> > +};
> > +
> > +/* Helper function to "reset" a previously matched node and undo the
> changes
> > +   made enough so that the node is treated as an irrelevant node.  */
> > +
> > +static inline void
> > +vect_slp_reset_pattern (slp_tree node) {
> > +  stmt_vec_info stmt_info = vect_orig_stmt (SLP_TREE_REPRESENTATIVE
> > +(node));
> > +  STMT_VINFO_IN_PATTERN_P (stmt_info) = false;
> > +  STMT_SLP_TYPE (stmt_info) = pure_slp;
> > +  SLP_TREE_REPRESENTATIVE (node) = stmt_info; }
> > +
> > +/* Pattern matcher for trying to match complex multiply and accumulate
> > +   and multiply and subtract patterns in SLP tree.
> > +   If the operation matches then IFN is set to the operation it matched and
> > +   the arguments to the two replacement statements are put in m_ops.
> > +
> > +   If no match is found then IFN is set to IFN_LAST and m_ops is unchanged.
> > +
> > +   This function matches the patterns shaped as:
> > +
> > +   double ax = (b[i+1] * a[i]) + (b[i] * a[i]);
> > +   double bx = (a[i+1] * b[i]) - (a[i+1] * b[i+1]);
> > +
> > +   c[i] = c[i] - ax;
> > +   c[i+1] = c[i+1] + bx;
> > +
> > +   If a match occurred then TRUE is returned, else FALSE.  The match is
> > +   performed after COMPLEX_MUL which would have done the majority of
> the work.
> > +   This function merely matches an ADD with a COMPLEX_MUL IFN.  The
> initial
> > +   match is expected to be in OP1 and the initial match operands in
> > + args0.  */
> > +
> > +internal_fn
> > +complex_fma_pattern::matches (complex_operation_t op,
> > +			      slp_tree_to_load_perm_map_t * /* perm_cache
> */,
> > +			      slp_tree *ref_node, vec<slp_tree> *ops) {
> > +  internal_fn ifn = IFN_LAST;
> > +
> > +  /* Find the two components.  We match Complex MUL first which
> reduces the
> > +     amount of work this pattern has to do.  After that we just match the
> > +     head node and we're done.:
> > +
> > +     * FMA: + +.
> > +
> > +     We need to ignore the two_operands nodes that may also match.
> > +     For that we can check if they have any scalar statements and also
> > +     check that it's not a permute node as we're looking for a normal
> > +     PLUS_EXPR operation.  */
> > +  if (op != CMPLX_NONE)
> > +    return IFN_LAST;
> > +
> > +  /* Find the two components.  We match Complex MUL first which
> reduces the
> > +     amount of work this pattern has to do.  After that we just match the
> > +     head node and we're done.:
> > +
> > +   * FMA: + + on a non-two_operands node.  */
> > +  slp_tree vnode = *ref_node;
> > +  if (SLP_TREE_LANE_PERMUTATION (vnode).exists ()
> > +      /* Need to exclude the plus two-operands node.  These are not
> marked
> > +	 so we have to infer it based on conditions.  */
> > +      || !SLP_TREE_SCALAR_STMTS (vnode).exists ()
> 
> as said earlier we shouldn't test this.  The existing lane permute should
> already cover this - where the test would better be
> 
>  SLP_TREE_CODE (vnode) == VEC_PERM_EXPR
> 
> > +      || !vect_match_expression_p (vnode, PLUS_EXPR))
> 
> But then it shouldn't match this (the vect_match_expression_p should only
> ever match SLP_TREE_CODE (vnode) != VEC_PERM_EXPR) anyway.
> 

How so? An FMA doesn't have a TWO_OPERANDS node as the root since the operations
Are always two PLUS operations.

The corresponding tree is

note:   SLP size 10 vs. limit 24.
note:   Final SLP tree for instance 0x48f68d0:
note:   node 0x4809870 (max_nunits=4, refcnt=2)
note:   op template: REALPART_EXPR <*_3> = _31;
note:     stmt 0 REALPART_EXPR <*_3> = _31;
note:     stmt 1 IMAGPART_EXPR <*_3> = _32;
note:     children 0x48098f8
note:   node 0x48098f8 (max_nunits=4, refcnt=2)
note:   op template: _31 = _12 + _29;
note:     stmt 0 _31 = _12 + _29;
note:     stmt 1 _32 = _11 + _30;
note:     children 0x4809980 0x4809a08
note:   node 0x4809980 (max_nunits=4, refcnt=2)
note:   op template: _12 = REALPART_EXPR <*_3>;
note:     stmt 0 _12 = REALPART_EXPR <*_3>;
note:     stmt 1 _11 = IMAGPART_EXPR <*_3>;
note:     load permutation { 0 1 }
note:   node 0x4809a08 (max_nunits=4, refcnt=2)
note:   op: VEC_PERM_EXPR
note:     stmt 0 _29 = _25 - _26;
note:     stmt 1 _30 = _27 + _28;
note:     lane permutation { 0[0] 1[1] }
note:     children 0x4809dc0 0x4809e48
note:   node 0x4809dc0 (max_nunits=1, refcnt=1)
note:   op template: _29 = _25 - _26;
note:     { }
note:     children 0x4809a90 0x4809c28
note:   node 0x4809a90 (max_nunits=4, refcnt=3)
note:   op template: _25 = _19 * _22;
note:     stmt 0 _25 = _19 * _22;
note:     stmt 1 _27 = _20 * _22;
note:     children 0x4809b18 0x4809ba0
note:   node 0x4809b18 (max_nunits=4, refcnt=2)
note:   op template: _19 = REALPART_EXPR <*_7>;
note:     stmt 0 _19 = REALPART_EXPR <*_7>;
note:     stmt 1 _20 = IMAGPART_EXPR <*_7>;
note:     load permutation { 0 1 }
note:   node 0x4809ba0 (max_nunits=4, refcnt=2)
note:   op template: _22 = REALPART_EXPR <*_5>;
note:     stmt 0 _22 = REALPART_EXPR <*_5>;
note:     stmt 1 _22 = REALPART_EXPR <*_5>;
note:     load permutation { 0 0 }
note:   node 0x4809c28 (max_nunits=4, refcnt=3)
note:   op template: _26 = _20 * _21;
note:     stmt 0 _26 = _20 * _21;
note:     stmt 1 _28 = _19 * _21;
note:     children 0x4809cb0 0x4809d38
note:   node 0x4809cb0 (max_nunits=4, refcnt=2)
note:   op template: _20 = IMAGPART_EXPR <*_7>;
note:     stmt 0 _20 = IMAGPART_EXPR <*_7>;
note:     stmt 1 _19 = REALPART_EXPR <*_7>;
note:     load permutation { 1 0 }
note:   node 0x4809d38 (max_nunits=4, refcnt=2)
note:   op template: _21 = IMAGPART_EXPR <*_5>;
note:     stmt 0 _21 = IMAGPART_EXPR <*_5>;
note:     stmt 1 _21 = IMAGPART_EXPR <*_5>;
note:     load permutation { 1 1 }
note:   node 0x4809e48 (max_nunits=1, refcnt=1)
note:   op template: _30 = _27 + _28;
note:     { }
note:     children 0x4809a90 0x4809c28

and after matching the MUL all you have are the ADD node going into a COMPLEX_MUL node.

> > +    return IFN_LAST;
> > +
> > +  slp_tree node = SLP_TREE_CHILDREN (vnode)[1];
> > +
> > +  if (vect_match_call_p (node, IFN_COMPLEX_MUL))
> > +    ifn = IFN_COMPLEX_FMA;
> > +  else if (vect_match_call_p (node, IFN_COMPLEX_MUL_CONJ))
> > +    ifn = IFN_COMPLEX_FMA_CONJ;
> > +  else
> > +    return IFN_LAST;
> > +
> > +  if (!vect_pattern_validate_optab (ifn, vnode))
> > +    return IFN_LAST;
> > +
> > +  vect_slp_reset_pattern (node);
> 
> I don't understand this ... it deserves a comment at least.

The previous pass detecting COMPLEX_MUL would have marked the
Instructions as being inside of a MUL pattern.  These need to be unmarked
As being part of the COMPLEX_MUL and instead be marked as COMPLEX_FMA.

> Having no testcases with this patch makes it impossible for me to dig in
> myself :/

Sorry, the tests would have made the file too big again.. The previous test for complex add
Added gcc/testsuite/gcc.dg/vect/complex/complex-operations.c which is an overarching test
Testing everything in one go.

The individual tests are split off from that large test.

> 
> Otherwise looks OK.
> 
> Thanks,
> Richard.
> 
> > +  ops->truncate (0);
> > +  ops->create (3);
> > +
> > +  if (ifn == IFN_COMPLEX_FMA)
> > +    {
> > +      ops->quick_push (SLP_TREE_CHILDREN (vnode)[0]);
> > +      ops->quick_push (SLP_TREE_CHILDREN (node)[1]);
> > +      ops->quick_push (SLP_TREE_CHILDREN (node)[0]);
> > +    }
> > +  else
> > +    {
> > +      ops->quick_push (SLP_TREE_CHILDREN (vnode)[0]);
> > +      ops->quick_push (SLP_TREE_CHILDREN (node)[0]);
> > +      ops->quick_push (SLP_TREE_CHILDREN (node)[1]);
> > +    }
> > +
> > +  return ifn;
> > +}
> > +
> > +/* Attempt to recognize a complex mul pattern.  */
> > +
> > +vect_pattern*
> > +complex_fma_pattern::recognize (slp_tree_to_load_perm_map_t
> *perm_cache,
> > +				slp_tree *node)
> > +{
> > +  auto_vec<slp_tree> ops;
> > +  complex_operation_t op
> > +    = vect_detect_pair_op (*node, true, &ops);
> > +  internal_fn ifn
> > +    = complex_fma_pattern::matches (op, perm_cache, node, &ops);
> > +  if (ifn == IFN_LAST)
> > +    return NULL;
> > +
> > +  return new complex_fma_pattern (node, &ops, ifn); }
> > +
> > +/* Perform a replacement of the detected complex mul pattern with the
> new
> > +   instruction sequences.  */
> > +
> > +void
> > +complex_fma_pattern::build (vec_info *vinfo) {
> > +  SLP_TREE_CHILDREN (*this->m_node).truncate (0);
> > +  SLP_TREE_CHILDREN (*this->m_node).safe_splice (this->m_ops);
> > +
> > +  complex_pattern::build (vinfo);
> > +}
> > +
> >
> /**********************************************************
> *********************
> >   * Pattern matching definitions
> >
> >
> **********************************************************
> ************
> > ********/
> >
> >
> >
> 
> --
> Richard Biener <rguenther@suse.de>
> SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409
> Nuernberg, Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)