middle-end: Fix ifcvt predicate generation for masked function calls

Up until now, due to a latent bug in the code for the ifcvt pass,
irrespective of the branch taken in a conditional statement, the
original condition for the if statement was used in masking the
function call.

Thus, for code such as:

  if (a[i] > limit)
    b[i] = fixed_const;
  else
    b[i] = fn (a[i]);

we would generate the following (wrong) if-converted tree code:

  _1 = a[i_1];
  _2 = _1 > limit;
  _3 = .MASK_CALL (fn, _1, _2);
  cstore_4 = _2 ? fixed_const : _3;

as opposed to the correct expected sequence:

  _1 = a[i_1];
  _2 = _1 > limit;
  _3 = ~_2;
  _4 = .MASK_CALL (fn, _1, _3);
  cstore_5 = _2 ? fixed_const : _4;

This patch ensures that the correct predicate mask generation is
carried out such that, upon autovectorization, the correct vector
lanes are selected in the vectorized function call.

gcc/ChangeLog:

	* tree-if-conv.cc (predicate_statements): Fix handling of
	predicated function calls.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/vect-fncall-mask.c: New.

2 files changed, 44 insertions, 1 deletions

diff --git a/gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c b/gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c
new file mode 100644
index 0000000..554488e
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/vect-fncall-mask.c
@@ -0,0 +1,31 @@
+/* { dg-do compile { target { aarch64*-*-* } } } */
+/* { dg-additional-options "-march=armv8.2-a+sve -fdump-tree-ifcvt-raw -Ofast" { target { aarch64*-*-* } } } */
+
+extern int __attribute__ ((simd, const)) fn (int);
+
+const int N = 20;
+const float lim = 101.0;
+const float cst =  -1.0;
+float tot =   0.0;
+
+float b[20];
+float a[20] = { [0 ... 9] = 1.7014118e39, /* If branch. */
+		[10 ... 19] = 100.0 };    /* Else branch.  */
+
+int main (void)
+{
+  #pragma omp simd
+  for (int i = 0; i < N; i += 1)
+    {
+      if (a[i] > lim)
+	b[i] = cst;
+      else
+	b[i] = fn (a[i]);
+      tot += b[i];
+    }
+  return (0);
+}
+
+/* { dg-final { scan-tree-dump {gimple_assign <gt_expr, _12, _1, 1.01e\+2, NULL>} ifcvt } } */
+/* { dg-final { scan-tree-dump {gimple_assign <bit_not_expr, _34, _12, NULL, NULL>} ifcvt } } */
+/* { dg-final { scan-tree-dump {gimple_call <.MASK_CALL, _3, fn, _2, _34>} ifcvt } } */
diff --git a/gcc/tree-if-conv.cc b/gcc/tree-if-conv.cc
index 0346a13..3b04d1e 100644
--- a/gcc/tree-if-conv.cc
+++ b/gcc/tree-if-conv.cc
@@ -2907,6 +2907,7 @@ predicate_statements (loop_p loop)
 		 This will cause the vectorizer to match the "in branch"
 		 clone variants, and serves to build the mask vector
 		 in a natural way.  */
+	      tree mask = cond;
 	      gcall *call = dyn_cast <gcall *> (gsi_stmt (gsi));
 	      tree orig_fn = gimple_call_fn (call);
 	      int orig_nargs = gimple_call_num_args (call);
@@ -2914,7 +2915,18 @@ predicate_statements (loop_p loop)
 	      args.safe_push (orig_fn);
 	      for (int i = 0; i < orig_nargs; i++)
 		args.safe_push (gimple_call_arg (call, i));
-	      args.safe_push (cond);
+	      /* If `swap', we invert the mask used for the if branch for use
+		 when masking the function call.  */
+	      if (swap)
+		{
+		  gimple_seq stmts = NULL;
+		  tree true_val
+		    = constant_boolean_node (true, TREE_TYPE (mask));
+		  mask = gimple_build (&stmts, BIT_XOR_EXPR,
+				       TREE_TYPE (mask), mask, true_val);
+		  gsi_insert_seq_before (&gsi, stmts, GSI_SAME_STMT);
+		}
+	      args.safe_push (mask);
 
 	      /* Replace the call with a IFN_MASK_CALL that has the extra
 		 condition parameter. */