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

2 files changed, 64 insertions, 25 deletions

diff --git a/include/llvm/CodeGen/MachineBasicBlock.h b/include/llvm/CodeGen/MachineBasicBlock.h
index 81912742fa..91dcf1c4c3 100644
--- a/include/llvm/CodeGen/MachineBasicBlock.h
+++ b/include/llvm/CodeGen/MachineBasicBlock.h
@@ -463,37 +463,57 @@ public:
     return Insts.insertAfter(I.getInstrIterator(), M);
   }
 
-  /// erase - Remove the specified element or range from the instruction list.
-  /// These functions delete any instructions removed.
+  /// Remove an instruction from the instruction list and delete it.
   ///
-  instr_iterator erase(instr_iterator I) {
-    return Insts.erase(I);
-  }
-  instr_iterator erase(instr_iterator I, instr_iterator E) {
-    return Insts.erase(I, E);
-  }
+  /// If the instruction is part of a bundle, the other instructions in the
+  /// bundle will still be bundled after removing the single instruction.
+  instr_iterator erase(instr_iterator I);
+
+  /// Remove an instruction from the instruction list and delete it.
+  ///
+  /// If the instruction is part of a bundle, the other instructions in the
+  /// bundle will still be bundled after removing the single instruction.
   instr_iterator erase_instr(MachineInstr *I) {
-    instr_iterator MII(I);
-    return erase(MII);
+    return erase(instr_iterator(I));
   }
 
-  iterator erase(iterator I);
+  /// Remove a range of instructions from the instruction list and delete them.
   iterator erase(iterator I, iterator E) {
     return Insts.erase(I.getInstrIterator(), E.getInstrIterator());
   }
+
+  /// Remove an instruction or bundle from the instruction list and delete it.
+  ///
+  /// If I points to a bundle of instructions, they are all erased.
+  iterator erase(iterator I) {
+    return erase(I, llvm::next(I));
+  }
+
+  /// Remove an instruction from the instruction list and delete it.
+  ///
+  /// If I is the head of a bundle of instructions, the whole bundle will be
+  /// erased.
   iterator erase(MachineInstr *I) {
-    iterator MII(I);
-    return erase(MII);
+    return erase(iterator(I));
   }
 
-  /// remove - Remove the instruction from the instruction list. This function
-  /// does not delete the instruction. WARNING: Note, if the specified
-  /// instruction is a bundle this function will remove all the bundled
-  /// instructions as well. It is up to the caller to keep a list of the
-  /// bundled instructions and re-insert them if desired. This function is
-  /// *not recommended* for manipulating instructions with bundles. Use
-  /// splice instead.
-  MachineInstr *remove(MachineInstr *I);
+  /// Remove the unbundled instruction from the instruction list without
+  /// deleting it.
+  ///
+  /// This function can not be used to remove bundled instructions, use
+  /// remove_instr to remove individual instructions from a bundle.
+  MachineInstr *remove(MachineInstr *I) {
+    assert(!I->isBundled() && "Cannot remove bundled instructions");
+    return Insts.remove(I);
+  }
+
+  /// Remove the possibly bundled instruction from the instruction list
+  /// without deleting it.
+  ///
+  /// If the instruction is part of a bundle, the other instructions in the
+  /// bundle will still be bundled after removing the single instruction.
+  MachineInstr *remove_instr(MachineInstr *I);
+
   void clear() {
     Insts.clear();
   }
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 {