[llvm] r274193 - CodeGen: Add an explicit BuildMI overload for MachineInstr&

[Duncan P. N. Exon Smith via llvm-commits]

Author: dexonsmith
Date: Wed Jun 29 19:10:17 2016
New Revision: 274193

URL: http://llvm.org/viewvc/llvm-project?rev=274193&view=rev
Log:
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.

Modified:
    llvm/trunk/include/llvm/CodeGen/MachineInstrBuilder.h

Modified: llvm/trunk/include/llvm/CodeGen/MachineInstrBuilder.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/CodeGen/MachineInstrBuilder.h?rev=274193&r1=274192&r2=274193&view=diff
==============================================================================
--- llvm/trunk/include/llvm/CodeGen/MachineInstrBuilder.h (original)
+++ llvm/trunk/include/llvm/CodeGen/MachineInstrBuilder.h Wed Jun 29 19:10:17 2016
@@ -265,6 +265,12 @@ inline MachineInstrBuilder BuildMI(Machi
   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(Machi
   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