With CONFIG_PROFILE_ALL_BRANCHES, the "if" macro converts the conditional to an array index. This can cause GCC to create horrible code. When there are nested ifs, the generated code uses register values to encode branching decisions.
Make it easier for GCC to optimize by keeping the conditional as a conditional rather than converting it to an integer. This shrinks the generated code quite a bit, and also makes the code sane enough for objtool to understand. Cc: rost...@goodmis.org Cc: valentin.schnei...@arm.com Cc: l...@amacapital.net Cc: brge...@gmail.com Cc: catalin.mari...@arm.com Cc: mi...@kernel.org Cc: dvlas...@redhat.com Cc: will.dea...@arm.com Cc: julien.thie...@arm.com Cc: torva...@linux-foundation.org Cc: dvyu...@google.com Cc: b...@alien8.de Cc: t...@linutronix.de Cc: james.mo...@arm.com Cc: l...@kernel.org Cc: h...@zytor.com Reported-by: Peter Zijlstra <pet...@infradead.org> Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Link: https://lkml.kernel.org/r/20190307174802.46fmpysxyo35hh43@treble --- include/linux/compiler.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -67,7 +67,7 @@ void ftrace_likely_update(struct ftrace_ .line = __LINE__, \ }; \ ______r = !!(cond); \ - ______f.miss_hit[______r]++; \ + ______r ? ______f.miss_hit[1]++ : ______f.miss_hit[0]++;\ ______r; \ })) #endif /* CONFIG_PROFILE_ALL_BRANCHES */
