[PATCH 3/3] PR jit/64810: fix for arm_option_override

[David Malcolm <dmalcolm at redhat dot com>]

libgccjit can make repeated in-process calls to the compiler code.

On arm I see failures where e.g. the top of the generated .s file has:
on the 1st iteration:
  .arch armv7-a
on the 2nd iteration:
  .cpu armv7-a
without changing any options.

What's happening is the 1st time through arm_option_override,
arm_selected_cpu is NULL, but is set to non-NULL at:
  arm_selected_cpu = arm_selected_arch;
The 2nd time through, arm_selected_cpu hasn't been reset, and so the
condition:

  if (arm_selected_arch)
    {
      if (arm_selected_cpu)
	{
	  /* Check for conflict between mcpu and march.  */

fires, and this clause fires:

	    /* -mcpu wins.  */
	    arm_selected_arch = NULL;

so we have a NULL arm_selected_arch and a non-NULL arm_selected_cpu.

The fix is to reset arm-specific state, setting
  arm_selected_{arch|cpu|tune}
to NULL at the top of arm_option_override, to prevent state from
previous in-process runs from affecting things.

With this, and the previous patches, most of the jit testsuite passes
on arm, with the only remaining failures being of the form:
  WARNING: Timed out executing test case
on the very large test cases (test-combination.c and test-threads.c).

OK for stage 4?

gcc/ChangeLog:
	PR jit/64810
	* config/arm/arm.c (arm_option_override): Set
	arm_selected_arch/cpu/tune to NULL on entry.
---
 gcc/config/arm/arm.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index 246298a..c7c0ecf 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -2627,6 +2627,10 @@ arm_gimplify_va_arg_expr (tree valist, tree type, gimple_seq *pre_p,
 static void
 arm_option_override (void)
 {
+  arm_selected_arch = NULL;
+  arm_selected_cpu = NULL;
+  arm_selected_tune = NULL;
+
   if (global_options_set.x_arm_arch_option)
     arm_selected_arch = &all_architectures[arm_arch_option];
 
-- 
1.8.5.3