Rename Instruction::isIdenticalTo to Instruction::isIdenticalToWhenDefined,

and introduce a new Instruction::isIdenticalTo which tests for full
identity, including the SubclassOptionalData flags. Also, fix the
Instruction::clone implementations to preserve the SubclassOptionalData
flags. Finally, teach several optimizations how to handle
SubclassOptionalData correctly, given these changes.

This fixes the counterintuitive behavior of isIdenticalTo not comparing
the full value, and clone not returning an identical clone, as well as
some subtle bugs that could be caused by these.

Thanks to Nick Lewycky for reporting this, and for an initial patch!

llvm-svn: 80038

1 files changed, 8 insertions, 0 deletions

diff --git a/llvm/lib/VMCore/Instruction.cpp b/llvm/lib/VMCore/Instruction.cpp
index e19ad1c16f9..332ecf9782d 100644
--- a/llvm/lib/VMCore/Instruction.cpp
+++ b/llvm/lib/VMCore/Instruction.cpp
@@ -168,6 +168,14 @@ const char *Instruction::getOpcodeName(unsigned OpCode) {
 /// identical to the current one.  This means that all operands match and any
 /// extra information (e.g. load is volatile) agree.
 bool Instruction::isIdenticalTo(const Instruction *I) const {
+  return isIdenticalTo(I) &&
+         SubclassOptionalData == I->SubclassOptionalData;
+}
+
+/// isIdenticalToWenDefined - This is like isIdenticalTo, except that it
+/// ignores the SubclassOptionalData flags, which specify conditions
+/// under which the instruction's result is undefined.
+bool Instruction::isIdenticalToWhenDefined(const Instruction *I) const {
   if (getOpcode() != I->getOpcode() ||
       getNumOperands() != I->getNumOperands() ||
       getType() != I->getType())