[committed] Make LRA default for ft32 and remove -mlra option

I was looking to clean up an old patch I'm carrying in my tester.  My first
thought was that ft32 was likely going to be deprecated because it wasn't using
LRA -- which in turn would mean the patch in question could just be removed.

But then I checked, ft32 has an LRA option and if turned on it gets the exact
same test results as with reload.  While the port mentions a failure with
sieve.c, that's been there since the port was introduced in 2015.

It's working well enough that I think just converting it is the right thing to
do.  The testsuite patch which precipitated this one will follow separately.
I've kept the -mlra option for compatibility sake, but it's ignored.

Pushing to the trunk.

gcc/
	* config/ft32/ft32.cc (ft32_lra_p): Remove.
	(TARGET_LRA_P): Likewise.
	* config/ft32/ft32.opt: Make -mlra ignored.
	* doc/invoke.texi: Adjust documentation for -mlra on ft32.

3 files changed, 3 insertions, 17 deletions

diff --git a/gcc/config/ft32/ft32.cc b/gcc/config/ft32/ft32.cc
index 3c6e5fb..80345dc 100644
--- a/gcc/config/ft32/ft32.cc
+++ b/gcc/config/ft32/ft32.cc
@@ -831,19 +831,6 @@ ft32_target_case_values_threshold (void)
   ft32_addr_space_legitimate_address_p
 
 
-// Enabling LRA gives the infamous
-//    internal compiler error: Max. number of generated reload insns per insn is achieved (90)
-// errors e.g. when compiling sieve.c
-
-static bool
-ft32_lra_p (void)
-{
-  return ft32_lra_flag;
-}
-
-#undef TARGET_LRA_P
-#define TARGET_LRA_P ft32_lra_p
-
 static bool
 reg_ok_for_base_p (rtx r, bool strict)
 {
diff --git a/gcc/config/ft32/ft32.opt b/gcc/config/ft32/ft32.opt
index cecc548..419c82a 100644
--- a/gcc/config/ft32/ft32.opt
+++ b/gcc/config/ft32/ft32.opt
@@ -23,8 +23,8 @@ Target Mask(SIM)
 Target the software simulator.
 
 mlra
-Target Var(ft32_lra_flag) Init(0) Save
-Use LRA instead of reload.
+Target RejectNegative Ignore
+Ignored, but preserved for backward compatibility.
 
 mnodiv
 Target Mask(NODIV)
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index fd6c0c4..8d92d46 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -25998,8 +25998,7 @@ I/O functions are needed.
 
 @opindex mlra
 @item -mlra
-Enable Local Register Allocation.  This is still experimental for FT32,
-so by default the compiler uses standard reload.
+Does nothing.  Preserved for backward compatibility.
 
 @opindex mnodiv
 @item -mnodiv