i386: Fix atan2l argument order [PR93743]

	PR target/93743
	* config/i386/i386.md (atan2xf3): Swap operands 1 and 2.
	(atan2<mode>3): Update operand order in the call to gen_atan2xf3.

testsuite/ChangeLog:

	PR target/93743
	* gcc.target/i386/pr93743.c : New test.

gcc/ChangeLog

+2020-02-16  Uroš Bizjak  <ubizjak@gmail.com>
+
+	PR target/93743
+	* config/i386/i386.md (atan2xf3): Swap operands 1 and 2.
+	(atan2<mode>3): Update operand order in the call to gen_atan2xf3.
+
 2020-02-15  Jason Merrill  <jason@redhat.com>
 
 	* doc/invoke.texi (C Dialect Options): Add -std=c++20.

gcc/config/i386/i386.md

@@ -15999,10 +15999,10 @@
 
 (define_insn "atan2xf3"
   [(set (match_operand:XF 0 "register_operand" "=f")
-        (unspec:XF [(match_operand:XF 1 "register_operand" "0")
-	            (match_operand:XF 2 "register_operand" "f")]
+        (unspec:XF [(match_operand:XF 2 "register_operand" "0")
+	            (match_operand:XF 1 "register_operand" "f")]
 	           UNSPEC_FPATAN))
-   (clobber (match_scratch:XF 3 "=2"))]
+   (clobber (match_scratch:XF 3 "=1"))]
   "TARGET_USE_FANCY_MATH_387
    && flag_unsafe_math_optimizations"
   "fpatan"
@@ -16026,7 +16026,7 @@
   emit_insn (gen_extend<mode>xf2 (op2, operands[2]));
   emit_insn (gen_extend<mode>xf2 (op1, operands[1]));
 
-  emit_insn (gen_atan2xf3 (op0, op2, op1));
+  emit_insn (gen_atan2xf3 (op0, op1, op2));
   emit_insn (gen_truncxf<mode>2 (operands[0], op0));
   DONE;
 })

gcc/testsuite/ChangeLog

+2020-02-16  Uroš Bizjak  <ubizjak@gmail.com>
+
+	PR target/93743
+	* gcc.target/i386/pr93743.c : New test.
+
 2020-02-15  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/93710 - poor diagnostic for array initializer.

gcc/testsuite/gcc.target/i386/pr93743.c

+/* { dg-do run } */
+/* { dg-options "-O2 -ffast-math -mfpmath=387" } */
+
+void
+__attribute__((noinline))
+test (long double x, long double y)
+{
+  long double ldbl_n = __builtin_atan2l (x, y);
+  long double ldbl_s = __builtin_atan2l (y, x);  // arguments swapped
+
+  if (ldbl_n < 1.L ||  1.L < ldbl_s)
+    __builtin_abort ();
+
+  double dbl_n = __builtin_atan2  (x, y);
+  double dbl_s = __builtin_atan2  (y, x);  // arguments swapped
+
+  if (dbl_n < 1. ||  1. < dbl_s)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  long double x = 0.922766L;
+  long double y = 0.080466L;
+
+  test (x, y);
+
+  return 0;
+}