Add getFirstInsertionPt() method.

getFirstInsertionPt() returns an iterator to the first insertion point in a
basic block. This is after all PHIs and any other instruction which is required
to be at the top of the basic block (like LandingPadInst).


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@137744 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/BasicBlock.h

@@ -145,6 +145,15 @@ public:
     return const_cast<BasicBlock*>(this)->getFirstNonPHIOrDbgOrLifetime();
   }
 
+  /// getFirstInsertionPt - Returns an iterator to the first instruction in this
+  /// block that is suitable for inserting a non-PHI instruction. In particular,
+  /// it skips all PHIs and LandingPad instructions. Returns 0 if there are no
+  /// non-PHI instructions.
+  iterator getFirstInsertionPt();
+  const_iterator getFirstInsertionPt() const {
+    return const_cast<BasicBlock*>(this)->getFirstInsertionPt();
+  }
+
   /// removeFromParent - This method unlinks 'this' from the containing
   /// function, but does not delete it.
   ///

lib/VMCore/BasicBlock.cpp

@@ -167,6 +167,12 @@ Instruction* BasicBlock::getFirstNonPHIOrDbgOrLifetime() {
   return &*i;
 }
 
+BasicBlock::iterator BasicBlock::getFirstInsertionPt() {
+  iterator InsertPt = getFirstNonPHI();
+  if (isa<LandingPadInst>(InsertPt)) ++InsertPt;
+  return InsertPt;
+}
+
 void BasicBlock::dropAllReferences() {
   for(iterator I = begin(), E = end(); I != E; ++I)
     I->dropAllReferences();