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From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: naked switches
Date: Thu, 08 Jul 2021 01:00:29 -0700
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Robert Finch <robfi680@gmail.com> writes:
> I have been working on a C/C++ like compiler. One feature supported in
> the compiler is naked switches. A naked switch omits the range
> checking code that is normally associated with the switch
> statement. Omitting this code can improve performance at the risk of a
> crash if invalid cases are processed. I am wondering if there is a
> similar option in other C compilers? Or would this just be an
> automatic optimization at high levels?

What range checking code are you referring to?  Can you give an example
in C that demonstrates the change in behavior?  How does a default:
label affect it?

> Normal Switch:
>
>   ;        	switch(x) {
>   ldo      $t0,64[$fp]
>   sge      $t1,$t0,#1		; x varies between 1 and 12
>   sle      $t2,$t0,#12
>   and      $t1,$t1,$t2
>   beq      $t1,TestSwitch_89
>   sub      $t0,$t0,#1
>   sll      $t0,$t0,#4
>   ldo      $t0,TestSwitch_116[$t0]
>   jmp      $t0
>
> Naked Switch
>   ;        	switch(x; naked) {
>   ldo      $t0,64[$fp]
>   sub      $t0,$t0,#1
>   sll      $t0,$t0,#4
>   ldo      $t0,TestSwitch_144[$t0]
>   jmp      $t0
>

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips
void Void(void) { Void(); } /* The recursive call of the void */