Source map fixes (#6550)

* Keep debug locations at function start

The `fn_prolog_epilog.debugInfo` test is failing otherwise, since there
was debug information associated to the nop instruction at the beginning
of the function.

* Do not clear the debug information when reaching the end of the source map

The last segment should extend to the end of the function.

* Propagate debug location from the function prolog to its first instruction

* Fix printing of epilogue location

The text parser no longer propagates locations to the epilogue, so we
should always print the location if there is one.

* Fix debug location smearing

The debug location of the last instruction should not smear into the
function epilogue, and a debug location from a previous function should
not smear into the prologue of the current function.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/wasm-stack.h b/src/wasm-stack.h
index 0b72774b6..5858d6f88 100644
--- a/src/wasm-stack.h
+++ b/src/wasm-stack.h
@@ -443,8 +443,13 @@ public:
   void emitDelegate(Try* curr) { writer.emitDelegate(curr); }
   void emitScopeEnd(Expression* curr) { writer.emitScopeEnd(curr); }
   void emitFunctionEnd() {
+    // Indicate the debug location corresponding to the end opcode
+    // that terminates the function code.
     if (func->epilogLocation.size()) {
       parent.writeDebugLocation(*func->epilogLocation.begin());
+    } else {
+      // The end opcode has no debug location.
+      parent.writeNoDebugLocation();
     }
     writer.emitFunctionEnd();
   }