5 files changed, 38 insertions, 26 deletions
diff --git a/lib/Transforms/IPO/StripDeadPrototypes.cpp b/lib/Transforms/IPO/StripDeadPrototypes.cpp
index fd22fdb37f..ca8a436844 100644
--- a/lib/Transforms/IPO/StripDeadPrototypes.cpp
+++ b/lib/Transforms/IPO/StripDeadPrototypes.cpp
@@ -1,4 +1,4 @@
-//===-- StripDeadPrototypes.cpp - Removed unused function declarations ----===//
+//===-- StripDeadPrototypes.cpp - Remove unused function declarations ----===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -8,7 +8,9 @@
 //===----------------------------------------------------------------------===//
 //
 // This pass loops over all of the functions in the input module, looking for 
-// dead declarations and removes them.
+// dead declarations and removes them. Dead declarations are declarations of
+// functions for which no implementation is available (i.e., declarations for
+// unused library functions).
 //
 //===----------------------------------------------------------------------===//
 
diff --git a/lib/Transforms/IPO/StructRetPromotion.cpp b/lib/Transforms/IPO/StructRetPromotion.cpp
index 77a35b4287..83ceb0dd0e 100644
--- a/lib/Transforms/IPO/StructRetPromotion.cpp
+++ b/lib/Transforms/IPO/StructRetPromotion.cpp
@@ -1,4 +1,4 @@
-//===-- StructRetPromotion.cpp - Promote sret arguments -000000------------===//
+//===-- StructRetPromotion.cpp - Promote sret arguments ------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -7,7 +7,16 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// TODO : Describe this pass.
+// This pass finds functions that return a struct (using a pointer to the struct
+// as the first argument of the function, marked with the 'sret' attribute) and
+// replaces them with a new function that simply returns each of the elements of
+// that struct (using multiple return values).
+//
+// This pass works under a number of conditions:
+//  1. The returned struct must not contain other structs
+//  2. The returned struct must only be used to load values from
+//  3. The placeholder struct passed in is the result of an alloca
+//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "sretpromotion"
diff --git a/lib/Transforms/Scalar/CodeGenPrepare.cpp b/lib/Transforms/Scalar/CodeGenPrepare.cpp
index 87c9374b2f..bc19114fa2 100644
--- a/lib/Transforms/Scalar/CodeGenPrepare.cpp
+++ b/lib/Transforms/Scalar/CodeGenPrepare.cpp
@@ -8,8 +8,8 @@
 //===----------------------------------------------------------------------===//
 //
 // This pass munges the code in the input function to better prepare it for
-// SelectionDAG-based code generation.  This works around limitations in it's
-// basic-block-at-a-time approach.  It should eventually be removed.
+// SelectionDAG-based code generation. This works around limitations in it's
+// basic-block-at-a-time approach. It should eventually be removed.
 //
 //===----------------------------------------------------------------------===//
 
diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 991b11110b..964fe90c46 100644
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -9,6 +9,23 @@
 //
 // This file implements the Jump Threading pass.
 //
+// Jump threading tries to find distinct threads of control flow running through
+// a basic block. This pass looks at blocks that have multiple predecessors and
+// multiple successors.  If one or more of the predecessors of the block can be
+// proven to always cause a jump to one of the successors, we forward the edge
+// from the predecessor to the successor by duplicating the contents of this
+// block.
+//
+// An example of when this can occur is code like this:
+//
+//   if () { ...
+//     X = 4;
+//   }
+//   if (X < 3) {
+//
+// In this case, the unconditional branch at the end of the first if can be
+// revectored to the false side of the second if.
+//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "jump-threading"
@@ -33,22 +50,6 @@ Threshold("jump-threading-threshold",
           cl::init(6), cl::Hidden);
 
 namespace {
-  /// This pass performs 'jump threading', which looks at blocks that have
-  /// multiple predecessors and multiple successors.  If one or more of the
-  /// predecessors of the block can be proven to always jump to one of the
-  /// successors, we forward the edge from the predecessor to the successor by
-  /// duplicating the contents of this block.
-  ///
-  /// An example of when this can occur is code like this:
-  ///
-  ///   if () { ...
-  ///     X = 4;
-  ///   }
-  ///   if (X < 3) {
-  ///
-  /// In this case, the unconditional branch at the end of the first if can be
-  /// revectored to the false side of the second if.
-  ///
   class VISIBILITY_HIDDEN JumpThreading : public FunctionPass {
   public:
     static char ID; // Pass identification
diff --git a/lib/Transforms/Scalar/LoopDeletion.cpp b/lib/Transforms/Scalar/LoopDeletion.cpp
index 1ea2f6ac9e..02a5ca98d9 100644
--- a/lib/Transforms/Scalar/LoopDeletion.cpp
+++ b/lib/Transforms/Scalar/LoopDeletion.cpp
@@ -7,10 +7,10 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements the Dead Loop Elimination Pass.  This pass is
-// responsible for eliminating loops with non-infinite computable trip counts
-// that have no side effects or volatile instructions, and do not contribute
-// to the computation of the function's return value.
+// This file implements the Dead Loop Deletion Pass. This pass is responsible
+// for eliminating loops with non-infinite computable trip counts that have no
+// side effects or volatile instructions, and do not contribute to the
+// computation of the function's return value.
 //
 //===----------------------------------------------------------------------===//