[PATCH] D45648: [WebAssembly] Fix a bug in MachineBasicBlock::findDebugLoc() call

[Heejin Ahn via Phabricator via llvm-commits]

aheejin created this revision.
aheejin added a reviewer: yurydelendik.
Herald added subscribers: llvm-commits, JDevlieghere, sunfish, jgravelle-google, sbc100, aprantl, dschuff, jfb.

- InsertPos is within the bacic block `Header`, so `findDebugLoc()`

should be call on not `MBB` but `Header` instead.

- In case a basic block that `findDebugLoc()` is called on does not have

a terminator or is empty, we should have a backup. (`findPrevDebugLoc()
returns UnknownLoc if no instruction is available to provide debug info)


Repository:
  rL LLVM

https://reviews.llvm.org/D45648

Files:
  lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp


Index: lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
===================================================================
--- lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
+++ lib/Target/WebAssembly/WebAssemblyCFGStackify.cpp
@@ -147,9 +147,12 @@
   }
 
   // Add the BLOCK.
-  MachineInstr *Begin = BuildMI(*Header, InsertPos, MBB.findDebugLoc(InsertPos),
-                                TII.get(WebAssembly::BLOCK))
-                            .addImm(int64_t(WebAssembly::ExprType::Void));
+  DebugLoc DL = InsertPos != Header->end()
+                    ? Header->findDebugLoc(InsertPos)
+                    : Header->findPrevDebugLoc(InsertPos);
+  MachineInstr *Begin =
+      BuildMI(*Header, InsertPos, DL, TII.get(WebAssembly::BLOCK))
+          .addImm(int64_t(WebAssembly::ExprType::Void));
 
   // Mark the end of the block.
   InsertPos = MBB.begin();
@@ -197,8 +200,10 @@
   while (InsertPos != MBB.end() &&
          InsertPos->getOpcode() == WebAssembly::END_LOOP)
     ++InsertPos;
-  MachineInstr *Begin = BuildMI(MBB, InsertPos, MBB.findDebugLoc(InsertPos),
-                                TII.get(WebAssembly::LOOP))
+
+  DebugLoc DL = InsertPos != MBB.end() ? MBB.findDebugLoc(InsertPos)
+                                       : MBB.findPrevDebugLoc(InsertPos);
+  MachineInstr *Begin = BuildMI(MBB, InsertPos, DL, TII.get(WebAssembly::LOOP))
                             .addImm(int64_t(WebAssembly::ExprType::Void));
 
   // Mark the end of the loop (using arbitrary debug location that branched


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