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

[Vladimir Ivanov]

> Make ConversionStub x86_32-specific only if possible. From what I see it 
> is only LIR_OpConvert in c1_LIR.hpp we have to deal with. I actually 
> can't see how it could be only 32-specific. Hmm?

I experimented with it, but it requires #ifdefs in c1_LIR.cpp/hpp which 
I don't like. So, I don't consider it as an option right now.

Best regards,
Vladimir Ivanov

>>> 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 
>>>>