[llvm] [CodeGen] Correctly handle non-standard cases in RemoveLoadsIntoFakeUses (PR #111551)

[Matt Arsenault via llvm-commits]

================
@@ -109,31 +112,38 @@ bool RemoveLoadsIntoFakeUses::runOnMachineFunction(MachineFunction &MF) {
       // reload of a spilled register.
       if (MI.getRestoreSize(TII)) {
         Register Reg = MI.getOperand(0).getReg();
-        assert(Reg.isPhysical() && "VReg seen in function with NoVRegs set?");
         // Don't delete live physreg defs, or any reserved register defs.
         if (!LivePhysRegs.available(Reg) || MRI->isReserved(Reg))
           continue;
-        // There should be an exact match between the loaded register and the
-        // FAKE_USE use. If not, this is a load that is unused by anything? It
-        // should probably be deleted, but that's outside of this pass' scope.
-        if (RegFakeUses.contains(Reg)) {
+        // There should typically be an exact match between the loaded register
+        // and the FAKE_USE, but sometimes regalloc will choose to load a larger
----------------
arsenm wrote:

Try to use MachineInstr::readsRegister and modifiesRegister queries? 

https://github.com/llvm/llvm-project/pull/111551