[LICM] Hoist guards from non-header blocks

This patch relaxes overconservative checks on whether or not we could write
memory before we execute an instruction. This allows us to hoist guards out of
loops even if they are not in the header block.

Differential Revision: https://reviews.llvm.org/D50891
Reviewed By: fedor.sergeev



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@346643 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Analysis/InstructionPrecedenceTracking.cpp

@@ -142,3 +142,8 @@ bool ImplicitControlFlowTracking::isSpecialInstruction(
   }
   return true;
 }
+
+bool MemoryWriteTracking::isSpecialInstruction(
+    const Instruction *Insn) const {
+  return Insn->mayWriteToMemory();
+}