some minor edits, link to Passes.html, make one point
I forgot about yesterday.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@43350 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/tutorial/LangImpl4.html b/docs/tutorial/LangImpl4.html
index 1048f73..8661b62 100644
--- a/docs/tutorial/LangImpl4.html
+++ b/docs/tutorial/LangImpl4.html
@@ -252,8 +252,9 @@
add from the program.</p>
<p>LLVM provides a wide variety of optimizations that can be used in certain
-circumstances. Unfortunately we don't have a good centralized description of
-what every pass does, but you can check out the ones that <tt>llvm-gcc</tt> or
+circumstances. Some <a href="../Passes.html">documentation about the various
+passes</a> is available, but it isn't very complete. Another good source of
+ideas is to look at the passes that <tt>llvm-gcc</tt> or
<tt>llvm-ld</tt> run to get started. The "<tt>opt</tt>" tool allows you to
experiment with passes from the command line, so you can see if they do
anything.</p>
@@ -410,6 +411,7 @@
ready> <b>sin(1.0);</b>
<em>Evaluated to 0.841471</em>
+
ready> <b>def foo(x) sin(x)*sin(x) + cos(x)*cos(x);</b>
Read function definition:
define double @foo(double %x) {
@@ -444,6 +446,27 @@
function name, and even allows you to have the JIT abort itself if any lazy
compilation is attempted.</p>
+<p>One interesting application of this is that we can now extend the language
+by writing arbitrary C++ code to implement operations. For example, if we add:
+</p>
+
+<div class="doc_code">
+<pre>
+/// putchard - putchar that takes a double and returns 0.
+extern "C"
+double putchard(double X) {
+ putchar((char)X);
+ return 0;
+}
+</pre>
+</div>
+
+<p>Now we can produce simple output to the console by using things like:
+"<tt>extern putchard(x); putchard(120);</tt>", which prints a lowercase 'x' on
+the console (120 is the ascii code for 'x'). Similar code could be used to
+implement file I/O, console input, and many other capabilities in
+Kaleidoscope.</p>
+
<p>This completes the JIT and optimizer chapter of the Kaleidoscope tutorial. At
this point, we can compile a non-Turing-complete programming language, optimize
and JIT compile it in a user-driven way. Next up we'll look into <a