1 files changed, 9 insertions, 5 deletions
diff --git a/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp b/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
index 4a0738dc3b7a..910a4e5e0d1a 100644
--- a/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ b/contrib/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -252,8 +252,7 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
 
   // Visit each instruction in the function.
   for (MachineBasicBlock &MBB : MF) {
-    for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E;) {
-      MachineInstr &MI = *I++;
+    for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) {
       assert(!WebAssembly::isArgument(MI.getOpcode()));
 
       if (MI.isDebugInstr() || MI.isLabel())
@@ -380,9 +379,14 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
         const TargetRegisterClass *RC = MRI.getRegClass(OldReg);
         Register NewReg = MRI.createVirtualRegister(RC);
         unsigned Opc = getLocalGetOpcode(RC);
-        InsertPt =
-            BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc), NewReg)
-                .addImm(LocalId);
+        // Use a InsertPt as our DebugLoc, since MI may be discontinuous from
+        // the where this local is being inserted, causing non-linear stepping
+        // in the debugger or function entry points where variables aren't live
+        // yet. Alternative is previous instruction, but that is strictly worse
+        // since it can point at the previous statement.
+        // See crbug.com/1251909, crbug.com/1249745
+        InsertPt = BuildMI(MBB, InsertPt, InsertPt->getDebugLoc(),
+                           TII->get(Opc), NewReg).addImm(LocalId);
         MO.setReg(NewReg);
         MFI.stackifyVReg(MRI, NewReg);
         Changed = true;