testsuite: Fix up lra effective target

Given the recent discussions on IRC started with Andrew P. mentioning that
an asm goto outputs test should have { target lra } and the lra effective
target in GCC 11/12 only returning 0 for PA and in 13/14 for PA/AVR, while
we clearly have 14 other targets which don't support LRA and a couple of
further ones which have an -mlra/-mno-lra switch (whatever default they
have), seems to me the effective target is quite broken.

The following patch rewrites it, such that it has a fast path for heavily
used targets which are for years known to use only LRA (just an
optimization) plus determines whether it is a LRA target or reload target
by scanning the -fdump-rtl-reload-details dump on an empty function,
LRA has quite a few always emitted messages in that case while reload has
none of those.

Tested on x86_64-linux and cross to s390x-linux, for the latter with both
make check-gcc RUNTESTFLAGS='--target_board=unix/-mno-lra dg.exp=pr107385.c'
where the test is now UNSUPPORTED and
make check-gcc RUNTESTFLAGS='--target_board=unix/-mlra dg.exp=pr107385.c'
where it fails because I don't have libc around.

There is one special case, NVPTX, which is a TARGET_NO_REGISTER_ALLOCATION
target.  I think claiming for it that it is a lra target is strange (even
though it effectively returns true for targetm.lra_p ()), unsure if it
supports asm goto with outputs or not, if it does and we want to test it,
perhaps we should introduce asm_goto_outputs effective target and use
lra || nvptx-*-* for that?

2024-02-17  Jakub Jelinek  <jakub@redhat.com>

	* lib/target-supports.exp (check_effective_target_lra): Rewrite
	to list some heavily used always LRA targets and otherwise check the
	-fdump-rtl-reload-details dump for messages specific to LRA.

1 files changed, 10 insertions, 3 deletions

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
index 82c73fa..6f4e25f 100644
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -13216,10 +13216,17 @@ proc check_effective_target_powerpc_as_p10_htm { } {
 # return 1 if LRA is supported.
 
 proc check_effective_target_lra { } {
-    if { [istarget hppa*-*-*] || [istarget avr-*-*] } {
-	return 0
+    # Start with heavily used targets which are known to always use LRA.
+    if { [istarget i?86-*-*] || [istarget x86_64-*-*]
+	 || [istarget aarch64*-*-*] || [istarget arm*-*-*]
+	 || [istarget powerpc*-*-*] || [istarget riscv*-*-*] } {
+	return 1
     }
-    return 1
+
+    # Otherwise check the reload dump for messages emitted solely by LRA.
+    return [check_no_messages_and_pattern lra "\\\*{9} Local #1: \\\*{9}" rtl-reload {
+        void foo (void) {}
+    } {-O2 -fdump-rtl-reload-details}] ;# LRA notes requires a detailed dump.
 }
 
 # Test whether optimizations are enabled ('__OPTIMIZE__') per the