Electrical – Renesas Compiler: KPIT vs GCC-Renesas (CyberThor)

compilergccrenesas

When looking around at Renesas (RL78) compilers, I noticed GCC mentioned a decent amount, but the links are different. Many of the older (<= 2015) URLs point to an India company, KPIT, and is mentioned in a Renesas press release. That website currently comes up with an empty web page for me.

Google searches for "renesas gcc" return gcc-renesas.com which is operated by a Romanian company named CyberThor Studios. Renesas's website doesn't mention CyberThor (that I've found).

I guess what I'm asking is…

What is the GCC for Renesas history?
KPIT and CyberThor look to be for-profit companies. Is their paid support any good?
Is it preferable to just use CC-RL from Renesas?
(bonus) Any experience comparing CC-RL to (currently CyberThor's) GCC code? Things like better bit manipulation, smaller code size, or faster execution with CC-RL maybe?

Cheers!

Best Answer

There are three tool chains available at present for the RL78 controllers.

They are available from GNU(CyberTHOR Studios Ltd.), IAR and Renesas.

The GNU tools are free and without limitations. https://gcc-renesas.com/

The IAR Workbench has a free evaluation version that is full featured for 30 days then restricts the object size to 16K bytes.

Without requesting a quote it's difficult to get hard numbers for an IAR license but from what pops up from web searches are amounts in the US$3000 range.

The Renesas CCRL compiler has a free version that is object size limited. The annual license subscription costs about US$300, the perpetual license is about US$1200.

Over the past 2 weeks I have been using the GNU tool chain from CyberTHOR. From looking at the object code output it appears to have a good code generator.

The RL78 has been around for some time but this is my first deep dive in to the architecture. It may just be me but it has been a lot of trouble to get the e2 Studio IDE and GNU tool chain installed on a Windows system and working reliably.

My company has a product developed by a third party that uses an RL78/G14 class controller. My task is to support the production testing of the product. To that end we need to develop code for the RL78 to do fundamental hardware level tests at the PCB assembly level.

I have digressed a bit so to get to your points:

1) For years Renesas has supported GNU tools for most of their controllers. CyberTHOR just seems to be the current partner. The KPIT GNU tool chain for the RL78 seems to be in archive mode.

2) As a Windows user I don't rebuild the tool chains from source so have not needed paid support from the distribution provider. As for using the compiler the online GNU documentation and the Renesas users forum are the support that has been helpful for me.

3) My opinion is that the GCC compiler is equivalent to CCRL. The Renesas CCRL compiler seems to require using the IDE (e2 Studio, or CS+ previously know as CubeSuite Plus). The e2 Studio IDE is Eclipse based and is a real learning experience for me. Renesas has a driver source code generator in the IDE. This works but is tricky to use. Renesas has other driver source code generators, Applilet3 and AP4 for RL78, that you may find helpful.

4) I have not yet observed the GNU tools output excessively clumsy code for the RL78 but I still have a lot to learn.

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My problem was actually that I was trying to change the baudrate back to the lower level during each command response. I misinterpreted the SD SPI spec, assuming that all commands needed to be communicated at the lower frequency.

Electronic – Why GCC compiler omitting some code

Since in one comment you state that "each CPU tick is worthy" I suggest using some inline assembly to make your delays loop just as you want. This solution is superior to the various volatile or -O0 because it makes clear what your intent is.

unsigned char i = 10;
__asm__ volatile ( "loop: subi    %0, 0x01\n\t"
                   "      brne    loop"
                   : "+rm" (i)
                   : /* no inputs */
                   : /* no dirty registers to decleare*/);

That should do the trick. The volatile thing is there to tell the compiler "I know this does not do anything, just keep it and trust me". The three asm "statements" are quite self explanatory, you can use any register instead of r24, I believe the compiler likes lower registers so you might want to use a high one. After the first : you should list output (read and write) c variables, and there's none, after the second : you should list input (ronly) c variables, again, there is none, and the third parameter is a comma separated list of modified registers, in this case r24. I am not sure if you should include also the status register since the ZERO flag changes of course, I did not include it.

edit edited answer as OP requested. Some notes.

The "+rm" before (i) means that you are letting the compiler decide to place i in memory or in a register. That's a good thing in most cases since the compiler can optimize better if it's free. In your case I believe you want to keep only the r constraint to force i to be a register.

Best Answer

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