[llvm] 42ffba0 - Add a clarifying a comment on CastInst::isNoopCast

[Philip Reames via llvm-commits]

Author: Philip Reames
Date: 2020-10-07T12:17:07-07:00
New Revision: 42ffba051894a66cf6d7b9a357e765a392d983ed

URL: https://github.com/llvm/llvm-project/commit/42ffba051894a66cf6d7b9a357e765a392d983ed
DIFF: https://github.com/llvm/llvm-project/commit/42ffba051894a66cf6d7b9a357e765a392d983ed.diff

LOG: Add a clarifying a comment on CastInst::isNoopCast

I made exactly the mistake described, so document the precondition.  It would be better to have an assert, but there is (currently) no "castIsValid" with purely type arguments.

Added: 
    

Modified: 
    llvm/include/llvm/IR/InstrTypes.h

Removed: 
    


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diff  --git a/llvm/include/llvm/IR/InstrTypes.h b/llvm/include/llvm/IR/InstrTypes.h
index 00aa79c4a239..c86448ea72cb 100644
--- a/llvm/include/llvm/IR/InstrTypes.h
+++ b/llvm/include/llvm/IR/InstrTypes.h
@@ -650,8 +650,8 @@ class CastInst : public UnaryInstruction {
   /// DataLayout argument is to determine the pointer size when examining casts
   /// involving Integer and Pointer types. They are no-op casts if the integer
   /// is the same size as the pointer. However, pointer size varies with
-  /// platform.
-  /// Determine if the described cast is a no-op cast.
+  /// platform.  Note that a precondition of this method is that the cast is
+  /// legal - i.e. the instruction formed with these operands would verify.
   static bool isNoopCast(
     Instruction::CastOps Opcode, ///< Opcode of cast
     Type *SrcTy,         ///< SrcTy of cast