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Re: [Patch][ARM]Don't put volatile memory access in IT block for cortex-m7


On 12/02/15 11:12, Terry Guo wrote:
> Hi there,
> 
> This patch intends to prevent gcc from putting volatile memory access into
> IT block for target like cortex-m7.
> 
> gcc/ChangeLog:
> 
> 2015-02-12  Terry Guo  <terry.guo@arm.com>
> 
> 	* config/arm/arm.c (arm_tune_cortex_m7): New global variable.
> 	* config/arm/arm.h (TARGET_NO_VOLATILE_CE): New macro.
>                 (arm_tune_cortex_m7): Declare new global variable.
> 	* config/arm/arm.md (arm_comparison_operator): Disabled if not allow
>                  volatile memory access in IT block.
> 
> gcc/testsuite/ChangeLog:
> 
> 2015-02-12  Terry Guo  <terry.guo@arm.com>
> 
> 	* gcc.target/arm/cortex-m7-it-volatile.c: New test.
> 

Not ok.

+/* Targets that don't support accessing volatile memory inside IT
block.  */
+#define TARGET_NO_VOLATILE_CE		(arm_tune_cortex_m7)

Please don't create feature bits that explicitly test for a particular
target.  Instead, define generic 'features' and then arrange for either
the architecture tables, or tuning tables (as appropriate) to enable
that feature.

See how arm_arch_arm_hwdiv is defined for how to do this.

R.


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