Handle IFN_COND_MUL in tree-ssa-math-opts.c

This patch extends the FMA handling in tree-ssa-math-opts.c so
that it can cope with conditional multiplications as well as
unconditional multiplications.  The addition or subtraction must then
have the same condition as the multiplication (at least for now).

E.g. we can currently fold:

  (IFN_COND_ADD cond (mul x y) z fallback)
    -> (IFN_COND_FMA cond x y z fallback)

This patch also allows:

  (IFN_COND_ADD cond (IFN_COND_MUL cond x y <whatever>) z fallback)
    -> (IFN_COND_FMA cond x y z fallback)

2019-07-30  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* tree-ssa-math-opts.c (convert_mult_to_fma): Add a mul_cond
	parameter.  When nonnull, make sure that the addition or subtraction
	has the same condition.
	(math_opts_dom_walker::after_dom_children): Try convert_mult_to_fma
	for CFN_COND_MUL too.

gcc/testsuite/
	* gcc.dg/vect/vect-cond-arith-7.c: New test.

From-SVN: r273905

1 files changed, 43 insertions, 28 deletions

diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index b7bbde4..3e0b238 100644
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -3044,6 +3044,8 @@ last_fma_candidate_feeds_initial_phi (fma_deferring_state *state,
 /* Combine the multiplication at MUL_STMT with operands MULOP1 and MULOP2
    with uses in additions and subtractions to form fused multiply-add
    operations.  Returns true if successful and MUL_STMT should be removed.
+   If MUL_COND is nonnull, the multiplication in MUL_STMT is conditional
+   on MUL_COND, otherwise it is unconditional.
 
    If STATE indicates that we are deferring FMA transformation, that means
    that we do not produce FMAs for basic blocks which look like:
@@ -3060,7 +3062,7 @@ last_fma_candidate_feeds_initial_phi (fma_deferring_state *state,
 
 static bool
 convert_mult_to_fma (gimple *mul_stmt, tree op1, tree op2,
-		     fma_deferring_state *state)
+		     fma_deferring_state *state, tree mul_cond = NULL_TREE)
 {
   tree mul_result = gimple_get_lhs (mul_stmt);
   tree type = TREE_TYPE (mul_result);
@@ -3174,6 +3176,9 @@ convert_mult_to_fma (gimple *mul_stmt, tree op1, tree op2,
 	  return false;
 	}
 
+      if (mul_cond && cond != mul_cond)
+	return false;
+
       if (cond)
 	{
 	  if (cond == result || else_value == result)
@@ -3785,38 +3790,48 @@ math_opts_dom_walker::after_dom_children (basic_block bb)
 	}
       else if (is_gimple_call (stmt))
 	{
-	  tree fndecl = gimple_call_fndecl (stmt);
-	  if (fndecl && gimple_call_builtin_p (stmt, BUILT_IN_NORMAL))
+	  switch (gimple_call_combined_fn (stmt))
 	    {
-	      switch (DECL_FUNCTION_CODE (fndecl))
+	    CASE_CFN_POW:
+	      if (gimple_call_lhs (stmt)
+		  && TREE_CODE (gimple_call_arg (stmt, 1)) == REAL_CST
+		  && real_equal (&TREE_REAL_CST (gimple_call_arg (stmt, 1)),
+				 &dconst2)
+		  && convert_mult_to_fma (stmt,
+					  gimple_call_arg (stmt, 0),
+					  gimple_call_arg (stmt, 0),
+					  &fma_state))
 		{
-		case BUILT_IN_POWF:
-		case BUILT_IN_POW:
-		case BUILT_IN_POWL:
-		  if (gimple_call_lhs (stmt)
-		      && TREE_CODE (gimple_call_arg (stmt, 1)) == REAL_CST
-		      && real_equal
-		      (&TREE_REAL_CST (gimple_call_arg (stmt, 1)),
-		       &dconst2)
-		      && convert_mult_to_fma (stmt,
-					      gimple_call_arg (stmt, 0),
-					      gimple_call_arg (stmt, 0),
-					      &fma_state))
-		    {
-		      unlink_stmt_vdef (stmt);
-		      if (gsi_remove (&gsi, true)
-			  && gimple_purge_dead_eh_edges (bb))
-			*m_cfg_changed_p = true;
-		      release_defs (stmt);
-		      continue;
-		    }
-		  break;
+		  unlink_stmt_vdef (stmt);
+		  if (gsi_remove (&gsi, true)
+		      && gimple_purge_dead_eh_edges (bb))
+		    *m_cfg_changed_p = true;
+		  release_defs (stmt);
+		  continue;
+		}
+	      break;
 
-		default:;
+	    case CFN_COND_MUL:
+	      if (convert_mult_to_fma (stmt,
+				       gimple_call_arg (stmt, 1),
+				       gimple_call_arg (stmt, 2),
+				       &fma_state,
+				       gimple_call_arg (stmt, 0)))
+
+		{
+		  gsi_remove (&gsi, true);
+		  release_defs (stmt);
+		  continue;
 		}
+	      break;
+
+	    case CFN_LAST:
+	      cancel_fma_deferring (&fma_state);
+	      break;
+
+	    default:
+	      break;
 	    }
-	  else
-	    cancel_fma_deferring (&fma_state);
 	}
       gsi_next (&gsi);
     }