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/wasm-stack.cpp b/src/wasm/wasm-stack.cpp
index 99aaf517e..dda47ffa6 100644
--- a/src/wasm/wasm-stack.cpp
+++ b/src/wasm/wasm-stack.cpp
@@ -2839,8 +2839,13 @@ void StackIRToBinaryWriter::write() {
         WASM_UNREACHABLE("unexpected op");
     }
   }
+  // 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();
 }