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

[Vladimir Kozlov]

Finally! Very good cleanup. Few notes.

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).

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

Thanks,
Vladimir

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