RFR: 8271883: Math CopySign optimization for x86

[Marcus G K Williams]

Intrinsic for Math.copySign is disabled on x86_64.

We can improve on generated c2 instructions for float and double, and this change adds optimized intrinsics for float and double Math.copySign.

**### Math.copySign(double)**
_From:_
  0x00007f7d606e5dac:   vmovq  %xmm1,%r10
  0x00007f7d606e5db1:   vmovq  %xmm0,%r11
  0x00007f7d606e5db6:   movabs $0x7fffffffffffffff,%r8
  0x00007f7d606e5dc0:   and    %r8,%r11
  0x00007f7d606e5dc3:   movabs $0x8000000000000000,%r8
  0x00007f7d606e5dcd:   and    %r8,%r10
  0x00007f7d606e5dd0:   or     %r11,%r10
  0x00007f7d606e5dd3:   vmovq  %r10,%xmm0                   

_To:_
  0x00007fc3c14c63ac:   movabs $0x7fffffffffffffff,%r10
  0x00007fc3c14c63b6:   vmovq  %r10,%xmm2
  0x00007fc3c14c63bb:   vpternlogq $0xe4,%xmm2,%xmm1,%xmm0

**### Math.copySign(float)**
_From:_
  0x00007ff8886e60ac:   vmovd  %xmm1,%r11d
  0x00007ff8886e60b1:   vmovd  %xmm0,%r10d
  0x00007ff8886e60b6:   and    $0x80000000,%r11d
  0x00007ff8886e60bd:   and    $0x7fffffff,%r10d
  0x00007ff8886e60c4:   or     %r10d,%r11d
  0x00007ff8886e60c7:   vmovd  %r11d,%xmm0
_To:_
  0x00007fc7d94c63ac:   mov    $0x7fffffff,%r10d
  0x00007fc7d94c63b2:   vmovd  %r10d,%xmm3
  0x00007fc7d94c63b7:   vpternlogd $0xe4,%xmm3,%xmm1,%xmm0

_**Performance of patch using updated test/micro/org/openjdk/bench/vm/compiler/Signum.java:**_
**BEFORE**
Signum._5_copySignFloatTest       avgt    5  2.442 ? 0.024  ns/op
Signum._7_copySignDoubleTest      avgt    5  2.400 ? 0.033  ns/op

**PATCH**
Signum._5_copySignFloatTest       avgt    5  2.029 ? 0.011  ns/op
Signum._7_copySignDoubleTest      avgt    5  2.029 ? 0.024  ns/op

**JTREG that covers this case:**
test/hotspot/jtreg/compiler/intrinsics/math/TestSignumIntrinsic.java

Signed-off-by: Marcus G K Williams <marcus.williams at intel.com>

-------------

Commit messages:
 - x86_64 copysign intrinsic

Changes: https://git.openjdk.java.net/jdk/pull/5005/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5005&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271883
  Stats: 122 lines in 5 files changed: 122 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5005.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5005/head:pull/5005

PR: https://git.openjdk.java.net/jdk/pull/5005