Add a comment mentioning that InstructionSimplify routines do,

in fact, resolve undef uses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173721 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/Analysis/InstructionSimplify.h b/include/llvm/Analysis/InstructionSimplify.h
index b653e799f7cdd742507e62cd3f08ac4db25f9a4f..06e443296761d0782be6dfb0a008aebf69e4a7ab 100644 (file)
--- a/include/llvm/Analysis/InstructionSimplify.h
+++ b/include/llvm/Analysis/InstructionSimplify.h
@@ -14,6 +14,12 @@
 // ("and i32 %x, %x" -> "%x").  If the simplification is also an instruction
 // then it dominates the original instruction.
 //
+// These routines implicitly resolve undef uses. The easiest way to be safe when
+// using these routines to obtain simplified values for existing instructions is
+// to always replace all uses of the instructions with the resulting simplified
+// values. This will prevent other code from seeing the same undef uses and
+// resolving them to different values.
+//
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_ANALYSIS_INSTRUCTIONSIMPLIFY_H