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, 32 insertions, 0 deletions

diff --git a/test/passes/strip-dwarf.bin.txt b/test/passes/strip-dwarf.bin.txt
new file mode 100644
index 000000000..2276090e7
--- /dev/null
+++ b/test/passes/strip-dwarf.bin.txt
@@ -0,0 +1,32 @@
+(module
+ (type $0 (func (result i32)))
+ (type $1 (func (param i32) (result i32)))
+ (type $2 (func))
+ (type $3 (func (param i32)))
+ (type $4 (func (param i32 i32)))
+ (import "env" "__wasm_call_ctors" (func $fimport$0))
+ (import "env" "dlmalloc" (func $fimport$1 (param i32) (result i32)))
+ (import "env" "dlfree" (func $fimport$2 (param i32)))
+ (import "env" "setThrew" (func $fimport$3 (param i32 i32)))
+ (import "env" "stackSave" (func $fimport$4 (result i32)))
+ (import "env" "stackAlloc" (func $fimport$5 (param i32) (result i32)))
+ (import "env" "stackRestore" (func $fimport$6 (param i32)))
+ (import "env" "__growWasmMemory" (func $fimport$7 (param i32) (result i32)))
+ (global $global$0 i32 (i32.const 1532))
+ (export "__wasm_call_ctors" (func $fimport$0))
+ (export "_Z3foov" (func $fimport$0))
+ (export "__errno_location" (func $0))
+ (export "setThrew" (func $fimport$3))
+ (export "malloc" (func $fimport$1))
+ (export "free" (func $fimport$2))
+ (export "__data_end" (global $global$0))
+ (export "stackSave" (func $fimport$4))
+ (export "stackAlloc" (func $fimport$5))
+ (export "stackRestore" (func $fimport$6))
+ (export "__growWasmMemory" (func $fimport$7))
+ (func $0 (; 8 ;) (type $0) (result i32)
+  (i32.const 1024)
+ )
+ ;; custom section "sourceMappingURL", size 15
+ ;; custom section "sourceMappingURL", size 15
+)