[8u] RFR: Revert parts of x86_64.ad to 8u upstream state

[Aleksey Shipilev]

Continuing to scrub the differences against 8u upstream. These are the funny bits in x86_64.ad:
  https://builds.shipilev.net/patch-openjdk-jdk8-aarch64/hotspot/src/cpu/x86/vm/x86_64.ad.sdiff.html

The first block got there via backport that reverts x86_64.ad to "upstream" state. But that state is
about jdk/jdk, not about jdk8u, where those white-space differences are actually present:
  http://hg.openjdk.java.net/shenandoah/jdk8/hotspot/rev/3f325d1f67d3

The second block is the leftover from two successive backports. The last one removed the only
matcher that used immU8, and so we don't need it. See:
  http://hg.openjdk.java.net/shenandoah/jdk8/hotspot/rev/ec5c2ccc5dbf
  http://hg.openjdk.java.net/shenandoah/jdk8/hotspot/rev/3b015c5e7a5e

sh/jdk8 patch:

diff -r 16898268d728 src/cpu/x86/vm/x86_64.ad
--- a/src/cpu/x86/vm/x86_64.ad  Thu Jul 18 18:22:24 2019 +0200
+++ b/src/cpu/x86/vm/x86_64.ad  Fri Jul 19 10:40:25 2019 +0200
@@ -213,5 +213,5 @@
 reg_class ptr_reg_with_rbp(RAX, RAX_H,
                            RDX, RDX_H,
-                           RBP, RBP_H,
+                           RBP, RBP_H,
                            RDI, RDI_H,
                            RSI, RSI_H,
@@ -810,5 +810,5 @@
   __ bind(done);
 }
-
+

 //=============================================================================
@@ -2940,14 +2940,4 @@
 %}

-operand immU8()
-%{
-  predicate((0 <= n->get_int()) && (n->get_int() <= 255));
-  match(ConI);
-
-  op_cost(5);
-  format %{ %}
-  interface(CONST_INTER);
-%}
-
 operand immI16()
 %{

Testing: hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey