[WebAssembly] Nullify DBG_VALUE_LISTs in DebugValueManager

WebAssemblyDebugValueManager class currently does not handle
DBG_VALUE_LIST instructions correctly for two reasons, which are
explained in https://bugs.llvm.org/show_bug.cgi?id=50361.

This effectively nullifies DBG_VALUE_LISTs in
WebAssemblyDebugValueManager so that the info will appear as "optimized
out" in debuggers but still be at least correct in the meantime.

Reviewed By: dschuff, jmorse

Differential Revision: https://reviews.llvm.org/D102589

1 files changed, 5 insertions, 5 deletions

diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
index 7ed224d..9bea203 100644
--- a/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -305,12 +305,11 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
         if (!MFI.isVRegStackified(OldReg)) {
           const TargetRegisterClass *RC = MRI.getRegClass(OldReg);
           Register NewReg = MRI.createVirtualRegister(RC);
-          auto InsertPt = std::next(MI.getIterator());
           if (UseEmpty[Register::virtReg2Index(OldReg)]) {
             unsigned Opc = getDropOpcode(RC);
-            MachineInstr *Drop =
-                BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc))
-                    .addReg(NewReg);
+            MachineInstr *Drop = BuildMI(MBB, std::next(MI.getIterator()),
+                                         MI.getDebugLoc(), TII->get(Opc))
+                                     .addReg(NewReg);
             // After the drop instruction, this reg operand will not be used
             Drop->getOperand(0).setIsKill();
             if (MFI.isFrameBaseVirtual() && OldReg == MFI.getFrameBaseVreg())
@@ -321,7 +320,8 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
 
             WebAssemblyDebugValueManager(&MI).replaceWithLocal(LocalId);
 
-            BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc))
+            BuildMI(MBB, std::next(MI.getIterator()), MI.getDebugLoc(),
+                    TII->get(Opc))
                 .addImm(LocalId)
                 .addReg(NewReg);
           }