Fix known typos

Sweep the codebase for common typos. Includes some changes to visible function
names that were misspelt.

llvm-svn: 200018
diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index dd67b45..2dafcb9 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -6740,7 +6740,7 @@
       return DAG.getNode(ISD::UINT_TO_FP, SDLoc(N), VT, N0);
   }
 
-  // The next optimizations are desireable only if SELECT_CC can be lowered.
+  // The next optimizations are desirable only if SELECT_CC can be lowered.
   // Check against MVT::Other for SELECT_CC, which is a workaround for targets
   // having to say they don't support SELECT_CC on every type the DAG knows
   // about, since there is no way to mark an opcode illegal at all value types
@@ -6797,7 +6797,7 @@
       return DAG.getNode(ISD::SINT_TO_FP, SDLoc(N), VT, N0);
   }
 
-  // The next optimizations are desireable only if SELECT_CC can be lowered.
+  // The next optimizations are desirable only if SELECT_CC can be lowered.
   // Check against MVT::Other for SELECT_CC, which is a workaround for targets
   // having to say they don't support SELECT_CC on every type the DAG knows
   // about, since there is no way to mark an opcode illegal at all value types
@@ -8265,7 +8265,7 @@
     // The width of the type must be a power of 2 and greater than 8-bits.
     // Otherwise the load cannot be represented in LLVM IR.
     // Moreover, if we shifted with a non-8-bits multiple, the slice
-    // will be accross several bytes. We do not support that.
+    // will be across several bytes. We do not support that.
     unsigned Width = User->getValueSizeInBits(0);
     if (Width < 8 || !isPowerOf2_32(Width) || (Shift & 0x7))
       return 0;