On 12/09/2013 11:51 AM, Michael Ellerman wrote: > On Wed, 2013-04-12 at 10:32:39 UTC, Anshuman Khandual wrote: >> Generic powerpc branch instruction analysis support added in the code >> patching library which will help the subsequent patch on SW based >> filtering of branch records in perf. This patch also converts and >> exports some of the existing local static functions through the header >> file to be used else where. >> >> diff --git a/arch/powerpc/include/asm/code-patching.h >> b/arch/powerpc/include/asm/code-patching.h >> index a6f8c7a..8bab417 100644 >> --- a/arch/powerpc/include/asm/code-patching.h >> +++ b/arch/powerpc/include/asm/code-patching.h >> @@ -22,6 +22,36 @@ >> #define BRANCH_SET_LINK 0x1 >> #define BRANCH_ABSOLUTE 0x2 >> >> +#define XL_FORM_LR 0x4C000020 >> +#define XL_FORM_CTR 0x4C000420 >> +#define XL_FORM_TAR 0x4C000460 >> + >> +#define BO_ALWAYS 0x02800000 >> +#define BO_CTR 0x02000000 >> +#define BO_CRBI_OFF 0x00800000 >> +#define BO_CRBI_ON 0x01800000 >> +#define BO_CRBI_HINT 0x00400000 >> + >> +/* Forms of branch instruction */ >> +int instr_is_branch_iform(unsigned int instr); >> +int instr_is_branch_bform(unsigned int instr); >> +int instr_is_branch_xlform(unsigned int instr); >> + >> +/* Classification of XL-form instruction */ >> +int is_xlform_lr(unsigned int instr); >> +int is_xlform_ctr(unsigned int instr); >> +int is_xlform_tar(unsigned int instr); >> + >> +/* Branch instruction is a call */ >> +int is_branch_link_set(unsigned int instr); >> + >> +/* BO field analysis (B-form or XL-form) */ >> +int is_bo_always(unsigned int instr); >> +int is_bo_ctr(unsigned int instr); >> +int is_bo_crbi_off(unsigned int instr); >> +int is_bo_crbi_on(unsigned int instr); >> +int is_bo_crbi_hint(unsigned int instr); > > > I think this is the wrong API. > > We end up with all these micro checks, which don't actually encapsulate much, > and don't implement the logic perf needs. If we had another user for this > level > of detail then it might make sense, but for a single user I think we're better > off just implementing the semantics it wants. >
Having a comprehensive list of branch instruction analysis APIs which some other user can also use in the future does not make it wrong. Being more elaborate and detailed makes this one a better choice than the API you have suggested below. > So that would be something more like: > > bool instr_is_return_branch(unsigned int instr); > bool instr_is_conditional_branch(unsigned int instr); > bool instr_is_func_call(unsigned int instr); > bool instr_is_indirect_func_call(unsigned int instr); > > > These would then encapsulate something like the logic in your 8/10 patch. You > can hopefully also optimise the checking logic in each routine because you > know > the exact semantics you're implementing. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
