[15] RFR (L): 7175279: Don't use x87 FPU on x86-64

[Vladimir Ivanov]

Thanks for the feedback, Vladimir.

> c1_CodeStubs.hpp - I think it should be stronger than assert to catch it 
> in product too (we can do check in product because it is not performance 
> critical code).

Do you prefer to see guarantee/fatal instead?

Frankly speaking, even the assert doesn't look warranted enough.
I put it there mainly to validate my own changes. I could have 
introduced ConversionStubs for x86-64 as well, but decided to simplify 
the implementation.

Considering x86-32 is the only consumer, I'd prefer to have 
ConversionStub x86_32-specific instead and completely hide it from other 
platforms, but it requires putting more #ifdefs in shared code which I 
don't like either.

So, if you see a value in having a runtime check in product binaries 
there, I'll put it there.

> c1_LinearScan.cpp - I think IA64 is used for Itanium. For 64-bit x86 we 
> use AMD64:
> 
> https://hg.openjdk.java.net/jdk/jdk/file/cfaa2457a60a/src/hotspot/share/utilities/macros.hpp#l456 

Yes, you are right. Good catch! :-)

Best regards,
Vladimir Ivanov

> On 12/17/19 4:50 AM, Vladimir Ivanov wrote:
>> http://cr.openjdk.java.net/~vlivanov/7175279/webrev.00/
>> https://bugs.openjdk.java.net/browse/JDK-7175279
>>
>> There was a major rewrite of math intrinsics which in 9 time frame 
>> which almost completely eliminated x87 code in x86-64 code base.
>>
>> Proposed patch removes the rest and makes x86-64 code x87-free.
>>
>> The main motivation for the patch is to completely eliminate 
>> non-strictfp behaving code in order to prepare the JVM for JEP 306 [1] 
>> and related enhancements [2].
>>
>> Most of the changes are in C1, but there is one case in template 
>> interpreter (java_lang_math_abs) which now uses 
>> StubRoutines::x86::double_sign_mask(). It forces its initialization to 
>> be moved to StubRoutines::initialize1().
>>
>> x87 instructions are made available only on x86-32.
>>
>> C1 changes involve removing FPU support on x86-64 and effectively make 
>> x86-specific support in linear scan allocator [2] x86-32-only.
>>
>> Testing: tier1-6, build on x86-23, linux-aarch64, linux-arm32.
>>
>> Best regards,
>> Vladimir Ivanov
>>
>> [1] https://bugs.openjdk.java.net/browse/JDK-8175916
>>
>> [2] https://bugs.openjdk.java.net/browse/JDK-8136414
>>
>> [3] 
>> http://hg.openjdk.java.net/jdk/jdk/file/ff7cd49f2aef/src/hotspot/cpu/x86/c1_LinearScan_x86.cpp 
>>