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authorLinus Torvalds <torvalds@linux-foundation.org>2019-03-20 18:26:17 +0100
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2019-05-09 21:25:13 +0200
commita15fd609ad53a631a927c6680e8fb606f42a712b (patch)
treef885028fcbbbc46022e69053638c88d984ef9df5 /arch/x86/kernel/ftrace_32.S
parenttracing: Fix documentation about disabling options using trace_options (diff)
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tracing: Simplify "if" macro code
Peter Zijlstra noticed that 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. Josh Poimboeuf found that replacing the define "if" macro from using the condition as an array index and incrementing the branch statics with an if statement itself, reduced the asm complexity and shrinks the generated code quite a bit. But this can be simplified even further by replacing the internal if statement with a ternary operator. Link: https://lkml.kernel.org/r/20190307174802.46fmpysxyo35hh43@treble Link: http://lkml.kernel.org/r/CAHk-=wiALN3jRuzARpwThN62iKd476Xj-uom+YnLZ4=eqcz7xQ@mail.gmail.com Reported-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reported-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'arch/x86/kernel/ftrace_32.S')
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