[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

llvm-svn: 346643

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/Analysis/InstructionPrecedenceTracking.cpp b/llvm/lib/Analysis/InstructionPrecedenceTracking.cpp
index c667c282281..b98975b006a 100644
--- a/llvm/lib/Analysis/InstructionPrecedenceTracking.cpp
+++ b/llvm/lib/Analysis/InstructionPrecedenceTracking.cpp
@@ -142,3 +142,8 @@ bool ImplicitControlFlowTracking::isSpecialInstruction(
   }
   return true;
 }
+
+bool MemoryWriteTracking::isSpecialInstruction(
+    const Instruction *Insn) const {
+  return Insn->mayWriteToMemory();
+}