CodeGen: Add an explicit BuildMI overload for MachineInstr&

Add an explicit overload to BuildMI for MachineInstr& to deal with
insertions inside of instruction bundles.

- Use it to re-implement MachineInstr* to give it coverage.

- Document how the overload for MachineBasicBlock::instr_iterator
  differs from that for MachineBasicBlock::iterator (the previous
  (implicit) overload for MachineInstr&).

- Add a comment explaining why the MachineInstr& and MachineInstr*
  overloads don't universally forward to the
  MachineBasicBlock::instr_iterator overload.

Thanks to Justin for noticing the API quirk.  While this doesn't fix any
known bugs -- all uses of BuildMI with a MachineInstr& were previously
using MachineBasicBlock::iterator -- it protects against future bugs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@274193 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/MachineInstrBuilder.h b/include/llvm/CodeGen/MachineInstrBuilder.h
index 233472bcda9b6babd4c7108f6d00c1bce360e612..da0afc320357601886bc96a2e06a61d10b01658e 100644 (file)
--- a/include/llvm/CodeGen/MachineInstrBuilder.h
+++ b/include/llvm/CodeGen/MachineInstrBuilder.h
@@ -265,6 +265,12 @@ inline MachineInstrBuilder BuildMI(MachineBasicBlock &BB,
   return MachineInstrBuilder(MF, MI).addReg(DestReg, RegState::Define);
 }
 
+/// This version of the builder inserts the newly-built instruction before
+/// the given position in the given MachineBasicBlock, and sets up the first
+/// operand as a destination virtual register.
+///
+/// If \c I is inside a bundle, then the newly inserted \a MachineInstr is
+/// added to the same bundle.
 inline MachineInstrBuilder BuildMI(MachineBasicBlock &BB,
                                    MachineBasicBlock::instr_iterator I,
                                    const DebugLoc &DL, const MCInstrDesc &MCID,
@@ -275,16 +281,20 @@ inline MachineInstrBuilder BuildMI(MachineBasicBlock &BB,
   return MachineInstrBuilder(MF, MI).addReg(DestReg, RegState::Define);
 }
 
-inline MachineInstrBuilder BuildMI(MachineBasicBlock &BB, MachineInstr *I,
+inline MachineInstrBuilder BuildMI(MachineBasicBlock &BB, MachineInstr &I,
                                    const DebugLoc &DL, const MCInstrDesc &MCID,
                                    unsigned DestReg) {
-  if (I->isInsideBundle()) {
-    MachineBasicBlock::instr_iterator MII(I);
-    return BuildMI(BB, MII, DL, MCID, DestReg);
-  }
+  // Calling the overload for instr_iterator is always correct.  However, the
+  // definition is not available in headers, so inline the check.
+  if (I.isInsideBundle())
+    return BuildMI(BB, MachineBasicBlock::instr_iterator(I), DL, MCID, DestReg);
+  return BuildMI(BB, MachineBasicBlock::iterator(I), DL, MCID, DestReg);
+}
 
-  MachineBasicBlock::iterator MII = I;
-  return BuildMI(BB, MII, DL, MCID, DestReg);
+inline MachineInstrBuilder BuildMI(MachineBasicBlock &BB, MachineInstr *I,
+                                   const DebugLoc &DL, const MCInstrDesc &MCID,
+                                   unsigned DestReg) {
+  return BuildMI(BB, *I, DL, MCID, DestReg);
 }
 
 /// This version of the builder inserts the newly-built instruction before the