From af4c6d9cf49c2c045ce680c25098e59f8d832f57 Mon Sep 17 00:00:00 2001
From: Thomas Lively <tlively@google.com>
Date: Mon, 20 Apr 2026 16:24:30 -0700
Subject: [PATCH] [wasm-merge] Preserve function names when writing a profile

When wasm-merge writes a wasm-split profile, it uses names to identify functions. It is never correct to then throw those names away when writing the binary, because that would make the profile useless. To avoid this problem, have --output-manifest imply --debuginfo and preserve the function names.
---
 src/tools/wasm-merge.cpp      |  6 ++++--
 test/lit/help/wasm-merge.test |  3 ++-
 test/lit/merge/manifest.wat   | 27 ++++++++++++++++++++++++++-
 3 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/src/tools/wasm-merge.cpp b/src/tools/wasm-merge.cpp
index 24615804da1..2197bc27356 100644
--- a/src/tools/wasm-merge.cpp
+++ b/src/tools/wasm-merge.cpp
@@ -697,11 +697,13 @@ Input source maps can be specified by adding an -ism option right after the modu
          "",
          "Write a wasm-split manifest to the specified file. This manifest can "
          "be given to wasm-split to split the merged module along the lines of "
-         "the original modules.",
+         "the original modules. Implies --debuginfo to preserve function names "
+         "in the output module.",
          WasmMergeOption,
          Options::Arguments::One,
-         [&manifestFile](Options* o, const std::string& argument) {
+         [&](Options* o, const std::string& argument) {
            manifestFile = argument;
+           debugInfo = true;
          })
     .add("--rename-export-conflicts",
          "-rec",
diff --git a/test/lit/help/wasm-merge.test b/test/lit/help/wasm-merge.test
index c0c4ee726a1..8c94b13745c 100644
--- a/test/lit/help/wasm-merge.test
+++ b/test/lit/help/wasm-merge.test
@@ -38,7 +38,8 @@
 ;; CHECK-NEXT:                                        specified file. This manifest can be
 ;; CHECK-NEXT:                                        given to wasm-split to split the merged
 ;; CHECK-NEXT:                                        module along the lines of the original
-;; CHECK-NEXT:                                        modules.
+;; CHECK-NEXT:                                        modules. Implies --debuginfo to preserve
+;; CHECK-NEXT:                                        function names in the output module.
 ;; CHECK-NEXT:
 ;; CHECK-NEXT:   --rename-export-conflicts,-rec       Rename exports to avoid conflicts (rather
 ;; CHECK-NEXT:                                        than error)
diff --git a/test/lit/merge/manifest.wat b/test/lit/merge/manifest.wat
index b0d2ef213ad..c93b40cdef9 100644
--- a/test/lit/merge/manifest.wat
+++ b/test/lit/merge/manifest.wat
@@ -1,5 +1,6 @@
-;; RUN: wasm-merge %s first %s.second second %s.third third --output-manifest %t.manifest -S -o %t.wasm
+;; RUN: wasm-merge %s first %s.second second %s.third third --output-manifest %t.manifest -o %t.wasm
 ;; RUN: cat %t.manifest | filecheck %s
+;; RUN: wasm-dis %t.wasm -o - | filecheck %s --check-prefix MERGED
 
 ;; The first module is the primary module and does not appear in the manifest.
 ;; CHECK-NOT:  first
@@ -12,6 +13,30 @@
 ;; CHECK-NEXT: third
 ;; CHECK-NEXT: qux
 
+;; The binary should contain the original function names.
+;; MERGED:      (module
+;; MERGED-NEXT:  (type $0 (func))
+;; MERGED-NEXT:  (import "env" "imported_first" (func $imported_first))
+;; MERGED-NEXT:  (import "env" "imported_second" (func $imported_second))
+;; MERGED-NEXT:  (import "env" "imported_third" (func $imported_third))
+;; MERGED-NEXT:  (export "foo" (func $foo))
+;; MERGED-NEXT:  (export "bar" (func $bar))
+;; MERGED-NEXT:  (export "baz" (func $baz))
+;; MERGED-NEXT:  (export "qux" (func $qux))
+;; MERGED-NEXT:  (func $foo
+;; MERGED-NEXT:   (call $imported_first)
+;; MERGED-NEXT:  )
+;; MERGED-NEXT:  (func $bar
+;; MERGED-NEXT:   (nop)
+;; MERGED-NEXT:  )
+;; MERGED-NEXT:  (func $baz
+;; MERGED-NEXT:   (call $imported_second)
+;; MERGED-NEXT:  )
+;; MERGED-NEXT:  (func $qux
+;; MERGED-NEXT:   (call $imported_third)
+;; MERGED-NEXT:  )
+;; MERGED-NEXT: )
+
 (module
   (import "env" "imported_first" (func $imported_first))
   (func $foo (export "foo")