[PR104400] LRA: Modify exclude start hard register calculation for insn alternative

v850 target has an interesting insn alternative constraint 'e!r' where e
denotes even general regs and e is a subset of r.  We cannot just make
union of exclude start hard registers for e and r and should use only
exclude start hard registers of r.  The following patch implements this.

gcc/ChangeLog:

	PR rtl-optimization/104400
	* lra-constraints.cc (process_alt_operands): Don't make union of
	this_alternative_exclude_start_hard_regs when reg class in insn
	alternative covers other reg classes in the same alternative.

gcc/testsuite/ChangeLog:

	PR rtl-optimization/104400
	* gcc.target/v850/pr104400.c: New.
	* gcc.target/v850/v850.exp: New.

gcc/lra-constraints.cc

@@ -2498,9 +2498,15 @@ process_alt_operands (int only_alternative)
 		  if (mode == BLKmode)
 		    break;
 		  this_alternative = reg_class_subunion[this_alternative][cl];
+		  if (hard_reg_set_subset_p (this_alternative_set,
+					     reg_class_contents[cl]))
+		    this_alternative_exclude_start_hard_regs
+		      = ira_exclude_class_mode_regs[cl][mode];
+		  else if (!hard_reg_set_subset_p (reg_class_contents[cl],
+						   this_alternative_set))
+		    this_alternative_exclude_start_hard_regs
+		      |= ira_exclude_class_mode_regs[cl][mode];
 		  this_alternative_set |= reg_class_contents[cl];
-		  this_alternative_exclude_start_hard_regs
-		    |= ira_exclude_class_mode_regs[cl][mode];
 		  if (costly_p)
 		    {
 		      this_costly_alternative

gcc/testsuite/gcc.target/v850/pr104400.c

@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -mv850e3v5" } */
+
+double frob (double r)
+{
+    r = -r;
+    return r;
+}

gcc/testsuite/gcc.target/v850/v850.exp

@@ -0,0 +1,41 @@
+# Copyright (C) 2022 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# GCC testsuite that uses the `dg.exp' driver.
+
+# Exit immediately if this isn't an v850 target.
+if ![istarget v850*-*-*] then {
+  return
+}
+
+# Load support procs.
+load_lib gcc-dg.exp
+
+# If a testcase doesn't have special options, use these.
+global DEFAULT_CFLAGS
+if ![info exists DEFAULT_CFLAGS] then {
+    set DEFAULT_CFLAGS " -ansi -pedantic-errors"
+}
+
+# Initialize `dg'.
+dg-init
+
+# Main loop.
+dg-runtest [lsort [glob -nocomplain $srcdir/$subdir/*.\[cS\]]] \
+	"" $DEFAULT_CFLAGS
+
+# All done.
+dg-finish