Remove early aspirational language about DXIR standard (#3375)

Early on, the plan was to document DXIR similar to DXIL. There are no
current plans to do so. This updates the documentation to reflect that.

docs/DXIL.rst

@@ -11,13 +11,13 @@ Introduction
 
 This document presents the design of the DirectX Intermediate Language (DXIL) for GPU shaders. DXIL is intended to support a direct mapping of the HLSL programming language into Low-Level Virtual Machine Intermediate Representation (LLVM IR), suitable for consumption in GPU drivers. This version of the specification is based on LLVM 3.7 in the use of metadata syntax.
 
-We distinguish between DXIL, which is a low-level IR for GPU driver compilers, and DXIR, which is a high-level IR, more suitable for emission by IR producers, such as Clang. DXIR is transformed to DXIL by the optimizer. DXIR accepts high-level constructs, such as user-defined types, multi-dimensional arrays, matrices, and vectors. These, however, are not suitable for fast JIT-ing in the driver compilers, and so are lowered by the optimizer, such that DXIL works on simpler abstractions. Both DXIL and DXIR are derived from LLVM IR. This document does not describe DXIR.
+Prior to being converted into the low-level DXIL IR, a higher level IR is generated by codegen which is then transformed into DXIL by the optimizer. This lowers high-level constructs, such as user-defined types, multi-dimensional arrays, matrices, and vectors into simpler abstractions more suitable for fast JIT-ing in the driver compilers. DXIL is derived from LLVM IR.
 
 LLVM is quickly becoming a de facto standard in modern compilation technology. The LLVM framework offers several distinct features, such as a vibrant ecosystem, complete compilation framework, modular design, and reasonable documentation. We can leverage these to achieve two important objectives.
 
 First, unification of shader compilation tool chain. DXIL is a contract between IR producers, such as compilers for HLSL and other domain-specific languages, and IR consumers, such as IHV driver JIT compilers or offline XBOX shader compiler. In addition, the design provides for conversion the current HLSL IL, called DXBC IL in this document, to DXIL.
 
-Second, leveraging the LLVM ecosystem. Microsoft will publicly document DXIL and DXIR to attract domain language implementers and spur innovation. Using LLVM-based IR offers reduced entry costs for small teams, simply because small teams are likely to use LLVM and Clang as their main compilation framework. We will provide DXIL verifier to check consistency of generated DXIL.
+Second, leveraging the LLVM ecosystem. Microsoft will publicly document DXIL to attract domain language implementers and spur innovation. Using LLVM-based IR offers reduced entry costs for small teams, simply because small teams are likely to use LLVM and Clang as their main compilation framework. We will provide DXIL verifier to check consistency of generated DXIL.
 
 The following diagram shows how some of these components tie together::
 
@@ -30,7 +30,7 @@ The following diagram shows how some of these components tie together::
   |      |                    |            |
   v      v                    v            |
   +------+--------------------+---------+  |
-  |          High level IR (DXIR)       |  |
+  |          High level IR              |  |
   +-------------------------------------+  |
                     |                      |
                     |                      |
@@ -46,7 +46,7 @@ The following diagram shows how some of these components tie together::
                 v                      v
         Driver Compiler             Verifier
 
-The *dxbc2dxil* element in the diagram is a component that converts existing DXBC shader byte code into DXIL. The *Optimizer* element is a component that consumes DXIR, verifies it is valid, optimizes it, and produces a valid DXIL form. The *Verifier* element is a public component that verifies and signs DXIL. The *Linker* is a component that combines precompiled DXIL libraries with the entry function to produce a valid shader.
+The *dxbc2dxil* element in the diagram is a component that converts existing DXBC shader byte code into DXIL. The *Optimizer* element is a component that consumes the high level IR, verifies it is valid, optimizes it, and produces a valid DXIL form. The *Verifier* element is a public component that verifies and signs DXIL. The *Linker* is a component that combines precompiled DXIL libraries with the entry function to produce a valid shader.
 
 DXIL does not support the following HLSL features that were present in prior implementations.
 
@@ -67,7 +67,7 @@ The following principles are used to ease reuse with LLVM components and aid ext
 * DXIL uses a subset of LLVM IR constructs that makes sense for HLSL.
 * No modifications to the core LLVM IR; i.e., no new instructions or fundamental types.
 * Additional information is conveyed via metadata, LLVM intrinsics or external functions.
-* Name prefixes: 'llvm.dx.', 'llvm.dxil.', 'llvm.dxir.', 'dx.', 'dxil.', and 'dxir.' are reserved.
+* Name prefixes: 'llvm.dx.', 'llvm.dxil.', 'dx.', and 'dxil.' are reserved.
 
 LLVM IR has three equivalent forms: human-readable, binary (bitcode), and in-memory. DXIL is a binary format and is based on a subset of LLVM IR bitcode format. The document uses only human-readable form to describe DXIL.
 
@@ -160,9 +160,9 @@ Intrinsics typically refer to operations missing in the core LLVM IR. DXIL repre
 DXIL abstraction level
 ----------------------
 
-DXIL has level of abstraction similar to a 'scalarized' DXBC. DXIL is lower level IR than DXIR emitted by the front-end to be amenable to fast and robust JIT-ing in driver compilers.
+DXIL has level of abstraction similar to a 'scalarized' DXBC. DXIL is a lower level IR amenable to fast and robust JIT-ing in driver compilers.
 
-In particular, the following passes are performed to lower the HLSL/DXIR abstractions down to DXIL:
+In particular, the following passes are performed to lower the HLSL abstractions down to DXIL:
 
 * optimize function parameter copies
 * inline functions
@@ -260,8 +260,8 @@ Identifier mangling rules are the ones used by Clang 3.7 with the HLSL target.
 
 The following identifier prefixes are reserved:
 
-* dx.*, dxil.*, dxir.*
-* llvm.dx.*, llvm.dxil.*, llvm.dxir.*
+* dx.*, dxil.*
+* llvm.dx.*, llvm.dxil.*
 
 Address Width
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