Re: Use -ftls-model=local-exec for RTEMS by default?

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

On 20/07/2022 10:43, Sebastian Huber wrote:
> Hello,
> 
> RTEMS applications are usually fully statically linked together with the 
> operating system. So, we can use the -ftls-model=local-exec TLS model. 
> The default value for this option is defined in common.opt:
> 
> ftls-model=
> Common Joined RejectNegative Enum(tls_model) Var(flag_tls_default) 
> Init(TLS_MODEL_GLOBAL_DYNAMIC)
> -ftls-model=[global-dynamic|local-dynamic|initial-exec|local-exec]    
> Set the default thread-local storage code generation model.
> 
> Would it be possible to customize the default value for RTEMS?

I think this could be done by adding

#define CC1_SPEC "%{!ftls-model=*:-ftls-model=local-exec}"

to gcc/config/rtems.h. However, the CC1_SPEC is also defined by several 
targets. Would it be possible to add an OS_CC1_SPEC like this?

diff --git a/gcc/gcc.cc b/gcc/gcc.cc
index bb07cc244e3..7ddabc888b0 100644
--- a/gcc/gcc.cc
+++ b/gcc/gcc.cc
@@ -709,6 +709,12 @@ proper position among the other output files.  */
  #define CC1_SPEC ""
  #endif

+/* config.h can define OS_CC1_SPEC to provide extra args to cc1 and cc1plus
+   or operating system specific extra switch-translations.  */
+#ifndef OS_CC1_SPEC
+#define OS_CC1_SPEC ""
+#endif
+
  /* config.h can define CC1PLUS_SPEC to provide extra args to cc1plus
     or extra switch-translations.  */
  #ifndef CC1PLUS_SPEC
@@ -1194,7 +1200,7 @@ proper position among the other output files.  */
  static const char *asm_debug = ASM_DEBUG_SPEC;
  static const char *asm_debug_option = ASM_DEBUG_OPTION_SPEC;
  static const char *cpp_spec = CPP_SPEC;
-static const char *cc1_spec = CC1_SPEC;
+static const char *cc1_spec = CC1_SPEC OS_CC1_SPEC;
  static const char *cc1plus_spec = CC1PLUS_SPEC;
  static const char *link_gcc_c_sequence_spec = LINK_GCC_C_SEQUENCE_SPEC;
  static const char *link_ssp_spec = LINK_SSP_SPEC;

How does Ada get its default TLS model?

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