[llvm] [WebAssembly] Enable a limited amount of stackification for debug code (PR #136510)

[via llvm-commits]

================
@@ -262,36 +267,52 @@ static bool shouldRematerialize(const MachineInstr &Def,
 // LiveIntervals to handle complex cases.
 static MachineInstr *getVRegDef(unsigned Reg, const MachineInstr *Insert,
                                 const MachineRegisterInfo &MRI,
-                                const LiveIntervals &LIS) {
+                                const LiveIntervals *LIS) {
   // Most registers are in SSA form here so we try a quick MRI query first.
   if (MachineInstr *Def = MRI.getUniqueVRegDef(Reg))
     return Def;
 
   // MRI doesn't know what the Def is. Try asking LIS.
-  if (const VNInfo *ValNo = LIS.getInterval(Reg).getVNInfoBefore(
-          LIS.getInstructionIndex(*Insert)))
-    return LIS.getInstructionFromIndex(ValNo->def);
+  if (LIS != nullptr) {
+    SlotIndex InstIndex = LIS->getInstructionIndex(*Insert);
+    if (const VNInfo *ValNo = LIS->getInterval(Reg).getVNInfoBefore(InstIndex))
+      return LIS->getInstructionFromIndex(ValNo->def);
+  }
 
   return nullptr;
 }
 
 // Test whether Reg, as defined at Def, has exactly one use. This is a
 // generalization of MachineRegisterInfo::hasOneNonDBGUse that uses
-// LiveIntervals to handle complex cases.
-static bool hasOneNonDBGUse(unsigned Reg, MachineInstr *Def,
-                            MachineRegisterInfo &MRI, MachineDominatorTree &MDT,
-                            LiveIntervals &LIS) {
+// LiveIntervals to handle complex cases in optimized code.
+static bool hasSingleUse(unsigned Reg, MachineRegisterInfo &MRI,
+                         WebAssemblyFunctionInfo &MFI, bool Optimize,
+                         MachineInstr *Def, LiveIntervals *LIS) {
+  if (!Optimize) {
+    // We don't want to stackify DBG_VALUE operands since WASM stack locations
+    // are less useful and less widely supported than WASM local locations.
----------------
SingleAccretion wrote:

Added.

https://github.com/llvm/llvm-project/pull/136510