Fix PR2748. Avoid coalescing physical register with virtual register which would create illegal extract_subreg. e.g.

vr1024 = extract_subreg vr1025, 1
...
vr1024 = mov8rr AH
If vr1024 is coalesced with AH, the extract_subreg is now illegal since AH does not have a super-reg whose sub-register 1 is AH.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56118 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 0 deletions

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.h b/lib/CodeGen/SimpleRegisterCoalescing.h
index 41d1dfb..39c9071 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.h
+++ b/lib/CodeGen/SimpleRegisterCoalescing.h
@@ -223,6 +223,13 @@ namespace llvm {
     bool isProfitableToCoalesceToSubRC(unsigned SrcReg, unsigned DstReg,
                                        MachineBasicBlock *MBB);
 
+    /// HasIncompatibleSubRegDefUse - If we are trying to coalesce a virtual
+    /// register with a physical register, check if any of the virtual register
+    /// operand is a sub-register use or def. If so, make sure it won't result
+    /// in an illegal extract_subreg or insert_subreg instruction.
+    bool HasIncompatibleSubRegDefUse(MachineInstr *CopyMI,
+                                     unsigned VirtReg, unsigned PhysReg);
+
     /// RangeIsDefinedByCopyFromReg - Return true if the specified live range of
     /// the specified live interval is defined by a copy from the specified
     /// register.