[PATCH] Begin adding docs and IR-level support for the inalloca attribute

[Sean Silva]

================
Comment at: docs/LangRef.rst:750-756
@@ +749,9 @@
+
+    invoke.cont:
+      call void @f(%Foo* inalloca %arg)
+      call void @llvm.stackrestore()
+      ...
+
+    invoke.unwind:
+      call void @llvm.stackrestore()
+      ...
----------------
You aren't passing an argument to llvm.stackrestore

================
Comment at: docs/LangRef.rst:751
@@ +750,3 @@
+    invoke.cont:
+      call void @f(%Foo* inalloca %arg)
+      call void @llvm.stackrestore()
----------------
Is this meant to be a recursive invocation? (this BB seems to be in a function `define void @f`)

================
Comment at: docs/LangRef.rst:730-733
@@ +729,6 @@
+
+    To avoid stack leaks, frontends should free memory used for
+    ``inalloca`` calls with :ref:`llvm.stacksave <int_stacksave>` and
+    :ref:`llvm.stackrestore <int_stackrestore>`.  This can be done after
+    a call or on an unwind edge, as in the following example.
+
----------------
This really needs more explanation. You need to explicitly specify the circumstances under which a stack leak may or may not occur.

================
Comment at: docs/LangRef.rst:704
@@ +703,3 @@
+
+.. Warning:: This feature is unstable and not fully implemented.
+
----------------
You may want to consider breaking this out into a separate page while it is still unstable, like Andy did for the stackmap/patchpoint stuff (splitting it into its own page seems to have been a huge win there, as the document can go into more depth about certain things). The Sphinx Quickstart Template makes it super easy to do this <http://llvm.org/docs/SphinxQuickstartTemplate.html>.

================
Comment at: docs/LangRef.rst:720
@@ +719,3 @@
+
+    Any use of ``inalloca`` arguments must comply with the target's ABI.
+    ``inalloca`` cannot be applied to parameters that are passed in
----------------
The connection between IR-level stuff and the actual machine code that will be emitted for these sorts of delicate ABI things is really quite tenuous, so I would avoid speaking in generalities about complying with a target ABI.

I would suggest providing explicit examples of ABI's and generated machine code and how an inalloca complies/doesn't comply with the ABI.


http://llvm-reviews.chandlerc.com/D2173