vect: Support multiple lane-reducing operations for loop reduction [PR114440]

For lane-reducing operation(dot-prod/widen-sum/sad) in loop reduction, current
vectorizer could only handle the pattern if the reduction chain does not
contain other operation, no matter the other is normal or lane-reducing.

This patches removes some constraints in reduction analysis to allow multiple
arbitrary lane-reducing operations with mixed input vectypes in a loop
reduction chain. For example:

   int sum = 1;
   for (i)
     {
       sum += d0[i] * d1[i];      // dot-prod <vector(16) char>
       sum += w[i];               // widen-sum <vector(16) char>
       sum += abs(s0[i] - s1[i]); // sad <vector(8) short>
     }

The vector size is 128-bit vectorization factor is 16. Reduction statements
would be transformed as:

   vector<4> int sum_v0 = { 0, 0, 0, 1 };
   vector<4> int sum_v1 = { 0, 0, 0, 0 };
   vector<4> int sum_v2 = { 0, 0, 0, 0 };
   vector<4> int sum_v3 = { 0, 0, 0, 0 };

   for (i / 16)
     {
       sum_v0 = DOT_PROD (d0_v0[i: 0 ~ 15], d1_v0[i: 0 ~ 15], sum_v0);
       sum_v1 = sum_v1;  // copy
       sum_v2 = sum_v2;  // copy
       sum_v3 = sum_v3;  // copy

       sum_v0 = WIDEN_SUM (w_v0[i: 0 ~ 15], sum_v0);
       sum_v1 = sum_v1;  // copy
       sum_v2 = sum_v2;  // copy
       sum_v3 = sum_v3;  // copy

       sum_v0 = SAD (s0_v0[i: 0 ~ 7 ], s1_v0[i: 0 ~ 7 ], sum_v0);
       sum_v1 = SAD (s0_v1[i: 8 ~ 15], s1_v1[i: 8 ~ 15], sum_v1);
       sum_v2 = sum_v2;  // copy
       sum_v3 = sum_v3;  // copy
     }

    sum_v = sum_v0 + sum_v1 + sum_v2 + sum_v3;   // = sum_v0 + sum_v1

2024-03-22 Feng Xue <fxue@os.amperecomputing.com>

gcc/
	PR tree-optimization/114440
	* tree-vectorizer.h (vectorizable_lane_reducing): New function
	declaration.
	* tree-vect-stmts.cc (vect_analyze_stmt): Call new function
	vectorizable_lane_reducing to analyze lane-reducing operation.
	* tree-vect-loop.cc (vect_model_reduction_cost): Remove cost computation
	code related to	emulated_mixed_dot_prod.
	(vectorizable_lane_reducing): New function.
	(vectorizable_reduction): Allow multiple lane-reducing operations in
	loop reduction. Move some original lane-reducing related code to
	vectorizable_lane_reducing.
	(vect_transform_reduction): Adjust comments with updated example.

gcc/testsuite/
	PR tree-optimization/114440
	* gcc.dg/vect/vect-reduc-chain-1.c
	* gcc.dg/vect/vect-reduc-chain-2.c
	* gcc.dg/vect/vect-reduc-chain-3.c
	* gcc.dg/vect/vect-reduc-chain-dot-slp-1.c
	* gcc.dg/vect/vect-reduc-chain-dot-slp-2.c
	* gcc.dg/vect/vect-reduc-chain-dot-slp-3.c
	* gcc.dg/vect/vect-reduc-chain-dot-slp-4.c
	* gcc.dg/vect/vect-reduc-dot-slp-1.c

1 files changed, 2 insertions, 0 deletions

diff --git a/gcc/tree-vectorizer.h b/gcc/tree-vectorizer.h
index 1e2121a..d8be89c 100644
--- a/gcc/tree-vectorizer.h
+++ b/gcc/tree-vectorizer.h
@@ -2485,6 +2485,8 @@ extern loop_vec_info vect_create_loop_vinfo (class loop *, vec_info_shared *,
 extern bool vectorizable_live_operation (vec_info *, stmt_vec_info,
 					 slp_tree, slp_instance, int,
 					 bool, stmt_vector_for_cost *);
+extern bool vectorizable_lane_reducing (loop_vec_info, stmt_vec_info,
+					slp_tree, stmt_vector_for_cost *);
 extern bool vectorizable_reduction (loop_vec_info, stmt_vec_info,
 				    slp_tree, slp_instance,
 				    stmt_vector_for_cost *);