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

[Vladimir Kozlov]

On 12/19/19 10:40 AM, Vladimir Ivanov wrote:
> 
>> 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.

Okay, NOT_IA32( ShouldNotReachHere() ) with comment in c1_CodeStubs.hpp should be enough for now.

Vladimir K

> 
> 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