[x86] Allow address-size overrides for STOS[BWLQ] (PR9385)

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

diff --git a/docs/CodeGenerator.rst b/docs/CodeGenerator.rst
index 1f2dc6ca7f7f40035aa8a0873aa8e1341a3b3d3e..b89d2f426f388a25cb206b4095246ff33d2a8707 100644 (file)
--- a/docs/CodeGenerator.rst
+++ b/docs/CodeGenerator.rst
@@ -434,12 +434,12 @@ For example, consider this simple LLVM example:
 .. code-block:: llvm
 
   define i32 @test(i32 %X, i32 %Y) {
-    %Z = udiv i32 %X, %Y
+    %Z = sdiv i32 %X, %Y
     ret i32 %Z
   }
 
-The X86 instruction selector produces this machine code for the ``div`` and
-``ret`` (use "``llc X.bc -march=x86 -print-machineinstrs``" to get this):
+The X86 instruction selector might produce this machine code for the ``div`` and
+``ret``:
 
 .. code-block:: llvm
 
@@ -454,8 +454,8 @@ The X86 instruction selector produces this machine code for the ``div`` and
   %EAX = mov %reg1026           ;; 32-bit return value goes in EAX
   ret
 
-By the end of code generation, the register allocator has coalesced the
-registers and deleted the resultant identity moves producing the following
+By the end of code generation, the register allocator would coalesce the
+registers and delete the resultant identity moves producing the following
 code:
 
 .. code-block:: llvm
@@ -636,6 +636,18 @@ file (MCObjectStreamer).  MCAsmStreamer is a straight-forward implementation
 that prints out a directive for each method (e.g. ``EmitValue -> .byte``), but
 MCObjectStreamer implements a full assembler.
 
+For target specific directives, the MCStreamer has a MCTargetStreamer instance.
+Each target that needs it defines a class that inherits from it and is a lot
+like MCStreamer itself: It has one method per directive and two classes that
+inherit from it, a target object streamer and a target asm streamer. The target
+asm streamer just prints it (``emitFnStart -> .fnstrart``), and the object
+streamer implement the assembler logic for it.
+
+To make llvm use these classes, the target initialization must call
+TargetRegistry::RegisterAsmStreamer and TargetRegistry::RegisterMCObjectStreamer
+passing callbacks that allocate the corresponding target streamer and pass it
+to createAsmStreamer or to the appropriate object streamer constructor.
+
 The ``MCContext`` class
 -----------------------
 
@@ -1614,7 +1626,7 @@ Implementing a Native Assembler
 ===============================
 
 Though you're probably reading this because you want to write or maintain a
-compiler backend, LLVM also fully supports building a native assemblers too.
+compiler backend, LLVM also fully supports building a native assembler.
 We've tried hard to automate the generation of the assembler from the .td files
 (in particular the instruction syntax and encodings), which means that a large
 part of the manual and repetitive data entry can be factored and shared with the