[PATCH] D113208: [WebAssembly] Fix debug locations for ExplicitLocals pass (#2)

[Wouter van Oortmerssen via Phabricator via llvm-commits]

This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGa320f877cec6: [WebAssembly] Fix debug locations for ExplicitLocals pass (authored by aardappel).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D113208/new/

https://reviews.llvm.org/D113208

Files:
  llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp


Index: llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
===================================================================
--- llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
+++ llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp
@@ -379,9 +379,14 @@
         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;


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