[M68k] incorrect assertion on move from CC register to data register

[TechnoElf]

The assertion "Need DR8 register to copy CCR" in M68kInstrInfo::copyPhysReg appears to be wrong. According to the Programmer's Reference Manual, MOVE from CCR takes a 16bit destination operand and zero extends the 5 bits in the CC register.

[TechnoElf]

Removing the assertion would be the obvious solution. At least the following change seems to compile code correctly:

--- a/llvm/lib/Target/M68k/M68kInstrInfo.cpp
+++ b/llvm/lib/Target/M68k/M68kInstrInfo.cpp
@@ -708,12 +708,12 @@ void M68kInstrInfo::copyPhysReg(MachineBasicBlock &MBB,
   bool ToSR = DstReg == M68k::SR;

   if (FromCCR) {
-    assert(M68k::DR8RegClass.contains(DstReg) &&
-           "Need DR8 register to copy CCR");
+    //assert(M68k::DR8RegClass.contains(DstReg) &&
+    //       "Need DR8 register to copy CCR");
     Opc = M68k::MOV8dc;
   } else if (ToCCR) {
-    assert(M68k::DR8RegClass.contains(SrcReg) &&
-           "Need DR8 register to copy CCR");
+    //assert(M68k::DR8RegClass.contains(SrcReg) &&
+    //       "Need DR8 register to copy CCR");
     Opc = M68k::MOV8cd;
   } else if (FromSR || ToSR)
     llvm_unreachable("Cannot emit SR copy instruction");

[llvmbot]

@llvm/issue-subscribers-backend-m68k

Author: Janis Heims (TechnoElf)

The assertion "Need DR8 register to copy CCR" in M68kInstrInfo::copyPhysReg appears to be wrong. According to the Programmer's Reference Manual, MOVE from CCR takes a 16bit destination operand and zero extends the 5 bits in the CC register.