[wwwdocs] Update gcc-8/changes.html for some IPA and x86 canges

[Jan Hubicka <hubicka at ucw dot cz>]

Hi,
this patch adds some documentation for what is new in IPA and x86.
For lto we should mention early-debug.  Richard, perhaps you can suggest
wording?

Honza

Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-8/changes.html,v
retrieving revision 1.41
diff -u -r1.41 changes.html
--- changes.html	12 Mar 2018 17:26:20 -0000	1.41
+++ changes.html	19 Mar 2018 21:07:07 -0000
@@ -42,9 +42,32 @@
 <!-- .................................................................. -->
 <h2 id="general">General Improvements</h2>
 <ul>
-  <li>The ipa-pure-const pass is extended to propagate malloc attribute, and the
-  corresponding warning option <code>Wsuggest-attribute=malloc</code> emits a
-  diagnostic for a function, which can be annotated with malloc attribute.</li>
+  <li>Inter-procedural optimization improvements:
+  <ul>
+    <li>Reworked runtime estimation metrics leading to more realistic guesses
+	driving inliner and clonning heuristics.</li>
+    <li>The ipa-pure-const pass is extended to propagate malloc attribute, and the
+	corresponding warning option <code>Wsuggest-attribute=malloc</code> emits a
+	diagnostic for a function, which can be annotated with malloc attribute.</li>
+  </ul>
+  <li>Profile driven optimization improvements:
+  <ul>
+    <li>New infrastructure for representing profile (both statically guessed
+	and profile feedback) which allows propagation of furhter information
+	about reliablility of the profile.</li>
+    <li>Number of improvements in profile updating code solving problems
+	found by new verification code.</li>
+    <li>Static detection of code which is not executed in valid run of the
+	program. This includes paths which triggers undefined behaviour
+	as well as call to functions declared with <code>cold</code> attribute.
+	Newly <code>noreturn</code> attribute does not imply all effects of
+	<code>cold</code> to make difference between <code>exit</code> (which
+	is <code>noreturn/code> and <code>abort</code> (which is in addition
+	not executed in valid runs).</li>
+    <li><code>-freorder-blocks-and-partition</code>, a pass splitting function
+	bodies into hot and cold regions, is now enabled by default at <code>-O2</code>
+	and higher for i386.</li>
+  </ul><li>
   <li>
     A new option <code>-fcf-protection=[full|branch|return|none]</code> is
     introduced to perform code instrumentation to increase program security by
@@ -435,6 +458,11 @@
 <ul>
   <li>
     The x86 port now supports the <code>naked</code> function attribute.</li>
+  <li>
+    Better tuning for <code>znver1</code> and Intel Core based CPUs.</li>
+  <li>
+    Vectorization costs metrics has been reworked leading to significant improvments
+    on some benchmarks</li>
   <li>GCC now supports the Intel CPU named Cannonlake through
     <code>-march=cannonlake</code>. The switch enables the AVX512VBMI,
     AVX512IFMA and SHA ISA extensions.</li>