[PATCH][PR91749][arm] FDPIC: Handle -mflip-thumb

[Christophe Lyon]

[Re-sending in plain text-mode, sorry for the duplicates]

Hi,

In PR91749, we have ICEs because -mflip-thumb switches to Thumb-1 (the
default target cpu does not support Thumb-2).

Although we already filter this in arm_configure_build_target, we
forgot to handle cases when the mode is changed via attributes (either
in the source code, or via -mflip-thumb).

This patch adds the same error message when trying to apply the
"thumb" attribute and the target does not support Thumb-2 (only if we
are in FDPIC mode, of course).

OK?

Thanks,

Christophe

gcc/ChangeLog:

2019-09-16  Christophe Lyon  <christophe.l...@linaro.org>

        PR target/91749
        * config/arm/arm.c (arm_valid_target_attribute_rec): Make sure the
        mode attributed is supported by FDPIC.


diff --git a/gcc/config/arm/arm.c b/gcc/config/arm/arm.c
index c452771..ceabe0a 100644
--- a/gcc/config/arm/arm.c
+++ b/gcc/config/arm/arm.c
@@ -31175,7 +31175,11 @@ arm_valid_target_attribute_rec (tree args, struct 
gcc_options *opts)
     {
       argstr = NULL;
       if (!strcmp (q, "thumb"))
-       opts->x_target_flags |= MASK_THUMB;
+       {
+         opts->x_target_flags |= MASK_THUMB;
+         if (TARGET_FDPIC && !arm_arch_thumb2)
+           sorry ("FDPIC mode is not supported in Thumb-1 mode");
+       }
 
       else if (!strcmp (q, "arm"))
        opts->x_target_flags &= ~MASK_THUMB;