From: Richard Biener <rguenther@suse.de>
Date: Fri, 30 Jan 2026 07:19:06 +0000 (+0100)
Subject: tree-optimization/123755 - more (len-)masked call fixes
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=HEAD;p=thirdparty%2Fgcc.git

tree-optimization/123755 - more (len-)masked call fixes

The testcase shows that we end up with (len-)masking a call even
when not semantically necessary.  The following aligns the condition
to apply len-masking with the condition to apply loop-masking, adjusting
downstream conditions to look at the chosen ifn instead of replicating
a possibly complex decision.

	PR tree-optimization/123755
	* tree-vect-stmts.cc (vectorizable_call): Adjust len-masking
	condition.  Simplify code generation.

	* gcc.dg/vect/vect-pr123755-2.c: New testcase.
---

diff --git a/gcc/testsuite/gcc.dg/vect/vect-pr123755-2.c b/gcc/testsuite/gcc.dg/vect/vect-pr123755-2.c
new file mode 100644
index 00000000000..7befef09edc
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-pr123755-2.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-ffast-math" } */
+
+double foo (double *a, double *b, double *c)
+{
+  double result = 0.0;
+  for (int i = 0; i < 1024; ++i)
+    result += i & 1 ? __builtin_fma (a[i], b[i], c[i]) : 0.0;
+  return result;
+}
diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
index ba2e4633258..e7d6b4c123a 100644
--- a/gcc/tree-vect-stmts.cc
+++ b/gcc/tree-vect-stmts.cc
@@ -3700,7 +3700,6 @@ vectorizable_call (vec_info *vinfo,
   internal_fn cond_fn = (internal_fn_mask_index (ifn) != -1
 			 ? ifn : get_conditional_internal_fn (ifn));
   internal_fn cond_len_fn = get_len_internal_fn (cond_fn);
-  int len_opno = internal_fn_len_index (cond_len_fn);
   vec_loop_masks *masks = (loop_vinfo ? &LOOP_VINFO_MASKS (loop_vinfo) : NULL);
   vec_loop_lens *lens = (loop_vinfo ? &LOOP_VINFO_LENS (loop_vinfo) : NULL);
   unsigned int nvectors = vect_get_num_copies (vinfo, slp_node);
@@ -3768,26 +3767,22 @@ vectorizable_call (vec_info *vinfo,
   bool masked_loop_p = loop_vinfo && LOOP_VINFO_FULLY_MASKED_P (loop_vinfo);
   bool len_loop_p = loop_vinfo && LOOP_VINFO_FULLY_WITH_LENGTH_P (loop_vinfo);
   unsigned int vect_nargs = nargs;
-  if (len_loop_p)
+  if (len_loop_p && (reduc_idx >= 0 || could_trap || mask_opno >= 0))
     {
-      if (len_opno >= 0)
-	{
-	  ifn = cond_len_fn;
-	  /* COND_* -> COND_LEN_* takes 2 extra arguments:LEN,BIAS.  */
-	  vect_nargs += 2;
-	  /* But unless there's a mask argument already we need that
-	     as well, and an else value.  */
-	  if (mask_opno == -1)
-	    vect_nargs += 2;
-	}
-      else if (reduc_idx >= 0)
-	gcc_unreachable ();
+      ifn = cond_len_fn;
+      /* COND_* -> COND_LEN_* takes 2 extra arguments:LEN,BIAS.  */
+      vect_nargs += 2;
+      /* But unless there's a mask argument already we need that
+	 as well, and an else value.  */
+      if (mask_opno == -1)
+	vect_nargs += 2;
     }
   else if (masked_loop_p && mask_opno == -1 && (reduc_idx >= 0 || could_trap))
     {
       ifn = cond_fn;
       vect_nargs += 2;
     }
+  int len_opno = internal_fn_len_index (ifn);
   if (clz_ctz_arg1)
     ++vect_nargs;
 
@@ -3828,7 +3823,7 @@ vectorizable_call (vec_info *vinfo,
 	      int varg = 0;
 	      /* Add the mask if necessary.  */
 	      if ((masked_loop_p || len_loop_p) && mask_opno == -1
-		  && (reduc_idx >= 0 || could_trap))
+		  && internal_fn_mask_index (ifn) != -1)
 		{
 		  gcc_assert (internal_fn_mask_index (ifn) == varg);
 		  if (masked_loop_p)
@@ -3854,7 +3849,7 @@ vectorizable_call (vec_info *vinfo,
 		}
 	      /* Add the else value if necessary.  */
 	      if ((masked_loop_p || len_loop_p) && mask_opno == -1
-		 && (reduc_idx >= 0 || could_trap))
+		  && internal_fn_else_index (ifn) != -1)
 		{
 		  gcc_assert (internal_fn_else_index (ifn) == varg);
 		  if (reduc_idx >= 0)