[docs] Typos and whitespace fixed in LTO docs.

[JDevlieghere]

Summary

While reading the LTO docs I fixed few small typos and whitespace issues.

[mehdi_amini]

docs/LinkTimeOptimization.rst

297

This is still part of the same sentence, I wouldn't use a capital here.

[JDevlieghere]

• Fixed capitalization of "which"

[JDevlieghere]

docs/LinkTimeOptimization.rst

297

You're totally right! I changed it for consistency with a previous sentence, which I now made lowercase in the updated diff. (I guess I should've done that in the first place...)

[mehdi_amini]

LGTM!

[JDevlieghere]

Would you mind landing this for me please? I don't have commit access yet.

docs/LinkTimeOptimization.rst

 ======================================================
 LLVM Link Time Optimization: Design and Implementation
 ======================================================
 
 .. contents::
    :local:
 
 Description
 ===========
 
 LLVM features powerful intermodular optimizations which can be used at link
-time.  Link Time Optimization (LTO) is another name for intermodular
+time. Link Time Optimization (LTO) is another name for intermodular
 optimization when performed during the link stage. This document describes the
 interface and design between the LTO optimizer and the linker.
 
 Design Philosophy
 =================
 
 The LLVM Link Time Optimizer provides complete transparency, while doing
 intermodular optimization, in the compiler tool chain. Its main goal is to let
 the developer take advantage of intermodular optimizations without making any
 significant changes to the developer's makefiles or build system. This is
 achieved through tight integration with the linker. In this model, the linker
-treates LLVM bitcode files like native object files and allows mixing and
+treats LLVM bitcode files like native object files and allows mixing and
 matching among them. The linker uses `libLTO`_, a shared object, to handle LLVM
 bitcode files. This tight integration between the linker and LLVM optimizer
 helps to do optimizations that are not possible in other models. The linker
 input allows the optimizer to avoid relying on conservative escape analysis.
 
 .. _libLTO-example:
 
 Example of link time optimization
 ---------------------------------
 
 The following example illustrates the advantages of LTO's integrated approach
 and clean interface. This example requires a system linker which supports LTO
-through the interface described in this document.  Here, clang transparently
+through the interface described in this document. Here, clang transparently
 invokes system linker.
 
 * Input source file ``a.c`` is compiled into LLVM bitcode form.
 * Input source file ``main.c`` is compiled into native object code.
 
 .. code-block:: c++
 
   --- a.h ---
.. code-block:: c++
   static int foo3() {
     foo4();
     return 10;
   }
 
   int foo1(void) {
     int data = 0;
 
-    if (i < 0) 
+    if (i < 0)
       data = foo3();
 
     data = data + 42;
     return data;
   }
 
   --- main.c ---
   #include <stdio.h>
**Compiler driver invokes link time optimizer separately.**
     In the above example, the optimizer can not remove ``foo2()`` without the
     linker's input because it is externally visible. This in turn prohibits the
     optimizer from removing ``foo3()``.
 
 **Use separate tool to collect symbol information from all object files.**
     In this model, a new, separate, tool or library replicates the linker's
     capability to collect information for link time optimization. Not only is
     this code duplication difficult to justify, but it also has several other
-    disadvantages.  For example, the linking semantics and the features provided
+    disadvantages. For example, the linking semantics and the features provided
     by the linker on various platform are not unique. This means, this new tool
     needs to support all such features and platforms in one super tool or a
     separate tool per platform is required. This increases maintenance cost for
     link time optimizer significantly, which is not necessary. This approach
-    also requires staying synchronized with linker developements on various
+    also requires staying synchronized with linker developments on various
     platforms, which is not the main focus of the link time optimizer. Finally,
     this approach increases end user's build time due to the duplication of work
     done by this separate tool and the linker itself.
 
 Multi-phase communication between ``libLTO`` and linker
 =======================================================
 
 The linker collects information about symbol definitions and uses in various
 link objects which is more accurate than any information collected by other
-tools during typical build cycles.  The linker collects this information by
+tools during typical build cycles. The linker collects this information by
 looking at the definitions and uses of symbols in native .o files and using
 symbol visibility information. The linker also uses user-supplied information,
 such as a list of exported symbols. LLVM optimizer collects control flow
 information, data flow information and knows much more about program structure
-from the optimizer's point of view.  Our goal is to take advantage of tight
+from the optimizer's point of view. Our goal is to take advantage of tight
 integration between the linker and the optimizer by sharing this information
 during various linking phases.
 
 Phase 1 : Read LLVM Bitcode Files
 ---------------------------------
 
 The linker first reads all object files in natural order and collects symbol
 information. This includes native object files as well as LLVM bitcode files.
 To minimize the cost to the linker in the case that all .o files are native
 object files, the linker only calls ``lto_module_create()`` when a supplied
-object file is found to not be a native object file.  If ``lto_module_create()``
+object file is found to not be a native object file. If ``lto_module_create()``
 returns that the file is an LLVM bitcode file, the linker then iterates over the
 module using ``lto_module_get_symbol_name()`` and
 ``lto_module_get_symbol_attribute()`` to get all symbols defined and referenced.
 This information is added to the linker's global symbol table.
 
 
-The lto* functions are all implemented in a shared object libLTO.  This allows
-the LLVM LTO code to be updated independently of the linker tool.  On platforms
+The lto* functions are all implemented in a shared object libLTO. This allows
+the LLVM LTO code to be updated independently of the linker tool. On platforms
 that support it, the shared object is lazily loaded.
 
 Phase 2 : Symbol Resolution
 ---------------------------
 
-In this stage, the linker resolves symbols using global symbol table.  It may
+In this stage, the linker resolves symbols using global symbol table. It may
 report undefined symbol errors, read archive members, replace weak symbols, etc.
 The linker is able to do this seamlessly even though it does not know the exact
-content of input LLVM bitcode files.  If dead code stripping is enabled then the
+content of input LLVM bitcode files. If dead code stripping is enabled then the
 linker collects the list of live symbols.
 
 Phase 3 : Optimize Bitcode Files
 --------------------------------
 
 After symbol resolution, the linker tells the LTO shared object which symbols
-are needed by native object files.  In the example above, the linker reports
+are needed by native object files. In the example above, the linker reports
 that only ``foo1()`` is used by native object files using
-``lto_codegen_add_must_preserve_symbol()``.  Next the linker invokes the LLVM
+``lto_codegen_add_must_preserve_symbol()``. Next the linker invokes the LLVM
 optimizer and code generators using ``lto_codegen_compile()`` which returns a
 native object file creating by merging the LLVM bitcode files and applying
 various optimization passes.
 
 Phase 4 : Symbol Resolution after optimization
 ----------------------------------------------
 
 In this phase, the linker reads optimized a native object file and updates the

 intention is to keep the interface as stable as possible even when the LLVM
 optimizer continues to evolve. It should even be possible for a completely
 different compilation technology to provide a different libLTO that works with
 their object files and the standard linker tool.
 
 ``lto_module_t``
 ----------------
 
-A non-native object file is handled via an ``lto_module_t``.  The following
+A non-native object file is handled via an ``lto_module_t``. The following
 functions allow the linker to check if a file (on disk or in a memory buffer) is
 a file which libLTO can process:
 
 .. code-block:: c
 
   lto_module_is_object_file(const char*)
   lto_module_is_object_file_for_target(const char*, const char*)
   lto_module_is_object_file_in_memory(const void*, size_t)

 
 The attributes of a symbol include the alignment, visibility, and kind.
 
 ``lto_code_gen_t``
 ------------------
 
 Once the linker has loaded each non-native object files into an
 ``lto_module_t``, it can request ``libLTO`` to process them all and generate a
-native object file.  This is done in a couple of steps.  First, a code generator
+native object file. This is done in a couple of steps. First, a code generator
 is created with:
 
 .. code-block:: c
 
   lto_codegen_create()
 
 Then, each non-native object file is added to the code generator with:
 
 .. code-block:: c
 
   lto_codegen_add_module(lto_code_gen_t, lto_module_t)
 
-The linker then has the option of setting some codegen options.  Whether or not
+The linker then has the option of setting some codegen options. Whether or not
 to generate DWARF debug info is set with:
-  
 .. code-block:: c
 
   lto_codegen_set_debug_model(lto_code_gen_t)
 
 Which kind of position independence is set with:
 
 .. code-block:: c
 
   lto_codegen_set_pic_model(lto_code_gen_t)
-  
 And each symbol that is referenced by a native object file or otherwise must not
 be optimized away is set with:
 
 .. code-block:: c
 
   lto_codegen_add_must_preserve_symbol(lto_code_gen_t, const char*)
 
 After all these settings are done, the linker requests that a native object file
 be created from the modules with the settings using:
 
 .. code-block:: c
 
   lto_codegen_compile(lto_code_gen_t, size*)
 
-which returns a pointer to a buffer containing the generated native object file.
+Which returns a pointer to a buffer containing the generated native object file.
 The linker then parses that and links it with the rest of the native object
 files.