Tighten up the erase/remove API for bundled instructions.

Most code is oblivious to bundles and uses the MBB::iterator which only
visits whole bundles. MBB::erase() operates on whole bundles at a time
as before.

MBB::remove() now refuses to remove bundled instructions. It is not safe
to remove all instructions in a bundle without deleting them since there
is no way of returning pointers to all the removed instructions.

MBB::remove_instr() and MBB::erase_instr() will now update bundle flags
correctly, lifting individual instructions out of bundles while leaving
the remaining bundle intact.

The MachineInstr convenience functions are updated so

  eraseFromParent() erases a whole bundle as before
  eraseFromBundle() erases a single instruction, leaving the rest of its bundle.
  removeFromParent() refuses to operate on bundled instructions, and
  removeFromBundle() lifts a single instruction out of its bundle.

These functions will no longer accidentally split or coalesce bundles -
bundle flags are updated to preserve the existing bundling, and explicit
bundleWith* / unbundleFrom* functions should be used to change the
instruction bundling.

This API update is still a work in progress. I am going to update APIs
first so they maintain bundle flags automatically when possible. Then
I'll add stricter verification of the bundle flags.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@170384 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 4 deletions

diff --git a/include/llvm/CodeGen/MachineInstr.h b/include/llvm/CodeGen/MachineInstr.h
index 57da779ca1..320cd0dc53 100644
--- a/include/llvm/CodeGen/MachineInstr.h
+++ b/include/llvm/CodeGen/MachineInstr.h
@@ -590,14 +590,33 @@ public:
   bool isIdenticalTo(const MachineInstr *Other,
                      MICheckType Check = CheckDefs) const;
 
-  /// removeFromParent - This method unlinks 'this' from the containing basic
-  /// block, and returns it, but does not delete it.
+  /// Unlink 'this' from the containing basic block, and return it without
+  /// deleting it.
+  ///
+  /// This function can not be used on bundled instructions, use
+  /// removeFromBundle() to remove individual instructions from a bundle.
   MachineInstr *removeFromParent();
 
-  /// eraseFromParent - This method unlinks 'this' from the containing basic
-  /// block and deletes it.
+  /// Unlink this instruction from its basic block and return it without
+  /// deleting it.
+  ///
+  /// If the instruction is part of a bundle, the other instructions in the
+  /// bundle remain bundled.
+  MachineInstr *removeFromBundle();
+
+  /// Unlink 'this' from the containing basic block and delete it.
+  ///
+  /// If this instruction is the header of a bundle, the whole bundle is erased.
+  /// This function can not be used for instructions inside a bundle, use
+  /// eraseFromBundle() to erase individual bundled instructions.
   void eraseFromParent();
 
+  /// Unlink 'this' form its basic block and delete it.
+  ///
+  /// If the instruction is part of a bundle, the other instructions in the
+  /// bundle remain bundled.
+  void eraseFromBundle();
+
   /// isLabel - Returns true if the MachineInstr represents a label.
   ///
   bool isLabel() const {