Add a --strip-dwarf pass (#2454)

This pass strips DWARF debug sections, but not other debug
sections. This is useful when emitting source maps, as we do
need the SourceMapURL section, but the DWARF sections are
not longer necessary (and we've seen a testcase where they
are massively large, so big the wasm can't even be loaded in
a browser...).

Also contains a trivial one-line fix in --extract-function which
was necessary to create the testcase here: that pass extracts
a function from a wasm file (like llvm-extract) but it didn't check
if an export already existed for the function.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/passes/Strip.cpp b/src/passes/Strip.cpp
index e85379003..ace745f87 100644
--- a/src/passes/Strip.cpp
+++ b/src/passes/Strip.cpp
@@ -62,6 +62,12 @@ Pass* createStripDebugPass() {
   });
 }
 
+Pass* createStripDWARFPass() {
+  return new Strip([&](const UserSection& curr) {
+    return curr.name.find(".debug") == 0 || curr.name.find("reloc..debug") == 0;
+  });
+}
+
 Pass* createStripProducersPass() {
   return new Strip([&](const UserSection& curr) {
     return curr.name == BinaryConsts::UserSections::Producers;