wasm-metadce: Improve name deduplication (#6138)

Avoid adding suffixes when we don't need them to keep names unique.

As background, the suffixes are not used by emcc at all, so they are just
for internal use in the tool. How that works is that metadce gets as input
the list of things the user cares about, with names for them, so it knows
the proper names to give imports and exports, and makes up names for
other things. Those made up names will not be read by the user, so we
can make them prettier as this PR does without breaking anything.

The main benefit of this PR is to make debugging easier. 

12 files changed, 59 insertions, 23 deletions

diff --git a/src/tools/wasm-metadce.cpp b/src/tools/wasm-metadce.cpp
index d81054d32..73d7c0691 100644
--- a/src/tools/wasm-metadce.cpp
+++ b/src/tools/wasm-metadce.cpp
@@ -307,9 +307,12 @@ struct MetaDCEGraph {
 private:
   // gets a unique name for the graph
   Name getName(std::string prefix1, std::string prefix2) {
+    auto base = prefix1 + '$' + prefix2;
+    if (nodes.find(base) == nodes.end()) {
+      return base;
+    }
     while (1) {
-      auto curr =
-        Name(prefix1 + '$' + prefix2 + '$' + std::to_string(nameIndex++));
+      Name curr = base + '$' + std::to_string(nameIndex++);
       if (nodes.find(curr) == nodes.end()) {
         return curr;
       }
diff --git a/test/metadce/corners.wast.dced.stdout b/test/metadce/corners.wast.dced.stdout
index 2c8983d24..3ab50a515 100644
--- a/test/metadce/corners.wast.dced.stdout
+++ b/test/metadce/corners.wast.dced.stdout
@@ -1,2 +1,2 @@
-unused: global$UNUSEDTOP$2
+unused: global$UNUSEDTOP
 unused: ignorable import
diff --git a/test/metadce/name_collision.wast b/test/metadce/name_collision.wast
new file mode 100644
index 000000000..62d11c697
--- /dev/null
+++ b/test/metadce/name_collision.wast
@@ -0,0 +1,18 @@
+(module
+  ;; This export is given the name "func$other" in the graph.text file, which
+  ;; collides with the internal name we give the function $other. A unique name
+  ;; should be generated for the function in the stdout that mentions it is
+  ;; unused, specifically
+  ;;
+  ;;  unused: func$other$0
+  ;;
+  ;; (the $0 suffix keeps it unique).
+  (export "test" (func $test))
+
+  ;; This function is used by the export.
+  (func $test)
+
+  ;; This function is not used, and as mentioned above it will be called
+  ;; func$other$0 in the output.
+  (func $other)
+)
diff --git a/test/metadce/name_collision.wast.dced b/test/metadce/name_collision.wast.dced
new file mode 100644
index 000000000..50e7010dc
--- /dev/null
+++ b/test/metadce/name_collision.wast.dced
@@ -0,0 +1,7 @@
+(module
+ (type $0 (func))
+ (export "test" (func $test))
+ (func $test (type $0)
+  (nop)
+ )
+)
diff --git a/test/metadce/name_collision.wast.dced.stdout b/test/metadce/name_collision.wast.dced.stdout
new file mode 100644
index 000000000..6fd813027
--- /dev/null
+++ b/test/metadce/name_collision.wast.dced.stdout
@@ -0,0 +1 @@
+unused: func$other$0
diff --git a/test/metadce/name_collision.wast.graph.txt b/test/metadce/name_collision.wast.graph.txt
new file mode 100644
index 000000000..591f82d76
--- /dev/null
+++ b/test/metadce/name_collision.wast.graph.txt
@@ -0,0 +1,7 @@
+[
+  {
+    "name": "func$other",
+    "root": true,
+    "export": "test"
+  }
+]
diff --git a/test/metadce/no-outside.wast.dced.stdout b/test/metadce/no-outside.wast.dced.stdout
index cb849efbb..22dffe9c8 100644
--- a/test/metadce/no-outside.wast.dced.stdout
+++ b/test/metadce/no-outside.wast.dced.stdout
@@ -1,4 +1,4 @@
-unused: export$wasm_func$4
-unused: export$wasm_func_unused$5
-unused: func$a_wasm_func$0
-unused: func$an_unused_wasm_func$1
+unused: export$wasm_func
+unused: export$wasm_func_unused
+unused: func$a_wasm_func
+unused: func$an_unused_wasm_func
diff --git a/test/metadce/outside.wast.dced.stdout b/test/metadce/outside.wast.dced.stdout
index d7ab8af72..3e2ea2251 100644
--- a/test/metadce/outside.wast.dced.stdout
+++ b/test/metadce/outside.wast.dced.stdout
@@ -1,3 +1,3 @@
-unused: export$wasm_func_unused$10
-unused: func$an_unused_wasm_func$1
-unused: global$__THREW__unused$4
+unused: export$wasm_func_unused
+unused: func$an_unused_wasm_func
+unused: global$__THREW__unused
diff --git a/test/metadce/rooted-export.wast.dced.stdout b/test/metadce/rooted-export.wast.dced.stdout
index 583f248d6..d6b97d555 100644
--- a/test/metadce/rooted-export.wast.dced.stdout
+++ b/test/metadce/rooted-export.wast.dced.stdout
@@ -1,4 +1,4 @@
-unused: export$wasm_func_a$4
-unused: export$wasm_tag_a$5
-unused: func$a_wasm_func$0
-unused: tag$a_wasm_tag$2
+unused: export$wasm_func_a
+unused: export$wasm_tag_a
+unused: func$a_wasm_func
+unused: tag$a_wasm_tag
diff --git a/test/metadce/spanning_cycle_unrooted.wast.dced.stdout b/test/metadce/spanning_cycle_unrooted.wast.dced.stdout
index 240c77b95..74701c9c9 100644
--- a/test/metadce/spanning_cycle_unrooted.wast.dced.stdout
+++ b/test/metadce/spanning_cycle_unrooted.wast.dced.stdout
@@ -1,3 +1,3 @@
-unused: func$a_wasm_func$0
+unused: func$a_wasm_func
 unused: outside_js_function
 unused: wasm_export
diff --git a/test/metadce/threaded_unrooted.wast.dced.stdout b/test/metadce/threaded_unrooted.wast.dced.stdout
index 0080ac5ae..b89392974 100644
--- a/test/metadce/threaded_unrooted.wast.dced.stdout
+++ b/test/metadce/threaded_unrooted.wast.dced.stdout
@@ -1,7 +1,7 @@
-unused: func$wasm_func_1$0
-unused: func$wasm_func_2$1
-unused: func$wasm_func_3$2
-unused: func$wasm_func_4$3
+unused: func$wasm_func_1
+unused: func$wasm_func_2
+unused: func$wasm_func_3
+unused: func$wasm_func_4
 unused: outside_js_function1
 unused: outside_js_function2
 unused: outside_js_function3
diff --git a/test/metadce/threaded_unrooted_cycle.wast.dced.stdout b/test/metadce/threaded_unrooted_cycle.wast.dced.stdout
index 0080ac5ae..b89392974 100644
--- a/test/metadce/threaded_unrooted_cycle.wast.dced.stdout
+++ b/test/metadce/threaded_unrooted_cycle.wast.dced.stdout
@@ -1,7 +1,7 @@
-unused: func$wasm_func_1$0
-unused: func$wasm_func_2$1
-unused: func$wasm_func_3$2
-unused: func$wasm_func_4$3
+unused: func$wasm_func_1
+unused: func$wasm_func_2
+unused: func$wasm_func_3
+unused: func$wasm_func_4
 unused: outside_js_function1
 unused: outside_js_function2
 unused: outside_js_function3