[PATCH] Prevent repetitive warnings for unrecognized processors and features (2nd attempt)

[Artyom Skrobov]

Hello,

Attached is the new patch, that includes an extensive refactoring of
MCSubtargetInfo and SubtargetFeatures, to prevent the repeated lookups of
CPU entries.
For the feature lookup failures, this still uses a set of strings to mark
the features whose lookup failed; but this set now belongs to the
MCSubtargetInfo instance.

OK to commit in this new form?


Later on, this will probably be accompanied with a front-end fix, as
suggested by Jim.


-----Original Message-----
From: Jim Grosbach [mailto:grosbach at apple.com] 
Sent: 30 January 2014 18:33
To: Artyom Skrobov
Cc: David Blaikie; llvm-commits at cs.uiuc.edu
Subject: Re: [llvm] r199886 - Prevent repetitive warnings for unrecognized
processors and features


On Jan 30, 2014, at 10:07 AM, Artyom Skrobov <Artyom.Skrobov at arm.com> wrote:

>> These are backend diagnostics only, right? I.e., they get issued by MC
>> when using developer tools like llvm-mc, llc, et. al.. They're
>> certainly not diagnostics we would ever expect to see from, e.g.,
>> clang or other user-level front-end. As such, I don't quite follow
>> why we should care about filtering duplicates at all. I don't oppose
>> uniquing them or anything, I just don't personally see it as a
>> priority. YMMV.
> 
> Yes, that's how it's supposed to be; but occasionally, these diagnostics
> "leak out" of the backend: one particular case that we're aware of, is
> 
> $ clang -target arm -mcpu=cortex-r4 -c test.c
> clang-3.5: warning: unknown platform, assuming -mfloat-abi=soft
> clang-3.5: warning: unknown platform, assuming -mfloat-abi=soft
> 'cortex-r4' is not a recognized processor for this target (ignoring
> processor)
> 'cortex-r4' is not a recognized processor for this target (ignoring
> processor)
> 'cortex-r4' is not a recognized processor for this target (ignoring
> processor)
> 'cortex-r4' is not a recognized processor for this target (ignoring
> processor)
> 'cortex-r4' is not a recognized processor for this target (ignoring
> processor)
> 'cortex-r4' is not a recognized processor for this target (ignoring
> processor)

Ew. That should be fixed in the front end to validate the argument to the
-mcpu option. I agree that's pretty bad as-is.
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