Update comments and documentation to reflect that GCSE and ValueNumbering are

deprecated by the GVN and GVNPRE passes.

llvm-svn: 51983

4 files changed, 14 insertions, 1 deletions

diff --git a/llvm/lib/Analysis/ValueNumbering.cpp b/llvm/lib/Analysis/ValueNumbering.cpp
index 98f04bd06e1..55323eaa9ed 100644
--- a/llvm/lib/Analysis/ValueNumbering.cpp
+++ b/llvm/lib/Analysis/ValueNumbering.cpp
@@ -10,6 +10,10 @@
 // This file implements the non-abstract Value Numbering methods as well as a
 // default implementation for the analysis group.
 //
+// The ValueNumbering analysis pass is mostly deprecated. It is only used by the
+// Global Common Subexpression Elimination pass, which is deprecated by the
+// Global Value Numbering pass (which does its value numbering on its own).
+//
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/Passes.h"
diff --git a/llvm/lib/Transforms/Scalar/GCSE.cpp b/llvm/lib/Transforms/Scalar/GCSE.cpp
index 35752bb6796..94cdcb1400f 100644
--- a/llvm/lib/Transforms/Scalar/GCSE.cpp
+++ b/llvm/lib/Transforms/Scalar/GCSE.cpp
@@ -9,9 +9,12 @@
 //
 // This pass is designed to be a very quick global transformation that
 // eliminates global common subexpressions from a function.  It does this by
-// using an existing value numbering implementation to identify the common
+// using an existing value numbering analysis pass to identify the common
 // subexpressions, eliminating them when possible.
 //
+// This pass is deprecated by the Global Value Numbering pass (which does a
+// better job with its own value numbering).
+//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "gcse"
diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index fcfe3c50587..e223281b425 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -10,6 +10,9 @@
 // This pass performs global value numbering to eliminate fully redundant
 // instructions.  It also performs simple dead load elimination.
 //
+// Note that this pass does the value numbering itself, it does not use the
+// ValueNumbering analysis passes.
+//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "gvn"
diff --git a/llvm/lib/Transforms/Scalar/GVNPRE.cpp b/llvm/lib/Transforms/Scalar/GVNPRE.cpp
index 1746fd80252..e0c869fbf8d 100644
--- a/llvm/lib/Transforms/Scalar/GVNPRE.cpp
+++ b/llvm/lib/Transforms/Scalar/GVNPRE.cpp
@@ -16,6 +16,9 @@
 // live ranges, and should be used with caution on platforms that are very 
 // sensitive to register pressure.
 //
+// Note that this pass does the value numbering itself, it does not use the
+// ValueNumbering analysis passes.
+//
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "gvnpre"