Merging r260703:

[oota-llvm.git] / docs / WritingAnLLVMBackend.rst

diff --git a/docs/WritingAnLLVMBackend.rst b/docs/WritingAnLLVMBackend.rst
index 35c853e5ed0fb10414bf7dee53b0818c470dbc01..fdadbb04e94f73bf4e7c6e415101dbc8a7a87e5b 100644 (file)
--- a/docs/WritingAnLLVMBackend.rst
+++ b/docs/WritingAnLLVMBackend.rst
@@ -51,7 +51,7 @@ These essential documents must be read before reading this document:
   Formation, SSA-based Optimization, Register Allocation, Prolog/Epilog Code
   Insertion, Late Machine Code Optimizations, and Code Emission.
 
-* :doc:`TableGenFundamentals` --- a document that describes the TableGen
+* :doc:`TableGen/index` --- a document that describes the TableGen
   (``tblgen``) application that manages domain-specific information to support
   LLVM code generation.  TableGen processes input from a target description
   file (``.td`` suffix) and generates C++ code that can be used for code
@@ -161,7 +161,7 @@ To get LLVM to actually build and link your target, you need to add it to the
 know about your target when parsing the ``--enable-targets`` option.  Search
 the configure script for ``TARGETS_TO_BUILD``, add your target to the lists
 there (some creativity required), and then reconfigure.  Alternatively, you can
-change ``autotools/configure.ac`` and regenerate configure by running
+change ``autoconf/configure.ac`` and regenerate configure by running
 ``./autoconf/AutoRegen.sh``.
 
 Target Machine
@@ -238,6 +238,12 @@ For some targets, you also need to support the following methods:
 * ``getTargetLowering()``
 * ``getJITInfo()``
 
+Some architectures, such as GPUs, do not support jumping to an arbitrary
+program location and implement branching using masked execution and loop using
+special instructions around the loop body. In order to avoid CFG modifications
+that introduce irreducible control flow not handled by such hardware, a target
+must call `setRequiresStructuredCFG(true)` when being initialized.
+
 In addition, the ``XXXTargetMachine`` constructor should specify a
 ``TargetDescription`` string that determines the data layout for the target
 machine, including characteristics such as pointer size, alignment, and
@@ -976,6 +982,7 @@ operands:
 This results in:
 
 .. code-block:: c++
+
   namespace X86 {
   namespace OpTypes {
   enum OperandType {