[WebAssembly] Refactor void return peephole using MaybeRewriteToFallt…

…hrough. NFC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@294652 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/WebAssembly/WebAssemblyPeephole.cpp

@@ -83,16 +83,18 @@ static bool MaybeRewriteToFallthrough(MachineInstr &MI, MachineBasicBlock &MBB,
   if (&MI != &MBB.back())
     return false;
 
-  // If the operand isn't stackified, insert a COPY to read the operand and
-  // stackify it.
-  MachineOperand &MO = MI.getOperand(0);
-  unsigned Reg = MO.getReg();
-  if (!MFI.isVRegStackified(Reg)) {
-    unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(Reg));
-    BuildMI(MBB, MI, MI.getDebugLoc(), TII.get(CopyLocalOpc), NewReg)
-        .addReg(Reg);
-    MO.setReg(NewReg);
-    MFI.stackifyVReg(NewReg);
+  if (FallthroughOpc != WebAssembly::FALLTHROUGH_RETURN_VOID) {
+    // If the operand isn't stackified, insert a COPY to read the operand and
+    // stackify it.
+    MachineOperand &MO = MI.getOperand(0);
+    unsigned Reg = MO.getReg();
+    if (!MFI.isVRegStackified(Reg)) {
+      unsigned NewReg = MRI.createVirtualRegister(MRI.getRegClass(Reg));
+      BuildMI(MBB, MI, MI.getDebugLoc(), TII.get(CopyLocalOpc), NewReg)
+          .addReg(Reg);
+      MO.setReg(NewReg);
+      MFI.stackifyVReg(NewReg);
+    }
   }
 
   // Rewrite the return.
@@ -188,9 +190,9 @@ bool WebAssemblyPeephole::runOnMachineFunction(MachineFunction &MF) {
             WebAssembly::COPY_V128);
         break;
       case WebAssembly::RETURN_VOID:
-        if (!DisableWebAssemblyFallthroughReturnOpt &&
-            &MBB == &MF.back() && &MI == &MBB.back())
-          MI.setDesc(TII.get(WebAssembly::FALLTHROUGH_RETURN_VOID));
+        Changed |= MaybeRewriteToFallthrough(
+            MI, MBB, MF, MFI, MRI, TII, WebAssembly::FALLTHROUGH_RETURN_VOID,
+            WebAssembly::INSTRUCTION_LIST_END);
         break;
       }