wasm-reduce: Fix setting of feature flags after loading (#3493)

We mistakenly did not set the flags to all, which meant that if the
features section was not present, we'd not have the proper features
set, leading to errors on writing.

5 files changed, 52 insertions, 6 deletions

diff --git a/auto_update_tests.py b/auto_update_tests.py
index 9f9a877b0..1135adeb2 100755
--- a/auto_update_tests.py
+++ b/auto_update_tests.py
@@ -114,8 +114,8 @@ def update_reduce_tests():
     for t in shared.get_tests(shared.get_test_dir('reduce'), ['.wast']):
         print('..', os.path.basename(t))
         # convert to wasm
-        support.run_command(shared.WASM_AS + [t, '-o', 'a.wasm'])
-        print(support.run_command(shared.WASM_REDUCE + ['a.wasm', '--command=%s b.wasm --fuzz-exec' % shared.WASM_OPT[0], '-t', 'b.wasm', '-w', 'c.wasm']))
+        support.run_command(shared.WASM_AS + [t, '-o', 'a.wasm', '-all'])
+        print(support.run_command(shared.WASM_REDUCE + ['a.wasm', '--command=%s b.wasm --fuzz-exec -all' % shared.WASM_OPT[0], '-t', 'b.wasm', '-w', 'c.wasm']))
         expected = t + '.txt'
         support.run_command(shared.WASM_DIS + ['c.wasm', '-o', expected])
 
diff --git a/check.py b/check.py
index fa9a060f8..499a201ce 100755
--- a/check.py
+++ b/check.py
@@ -159,8 +159,8 @@ def run_wasm_reduce_tests():
     for t in shared.get_tests(shared.get_test_dir('reduce'), ['.wast']):
         print('..', os.path.basename(t))
         # convert to wasm
-        support.run_command(shared.WASM_AS + [t, '-o', 'a.wasm'])
-        support.run_command(shared.WASM_REDUCE + ['a.wasm', '--command=%s b.wasm --fuzz-exec --detect-features ' % shared.WASM_OPT[0], '-t', 'b.wasm', '-w', 'c.wasm', '--timeout=4'])
+        support.run_command(shared.WASM_AS + [t, '-o', 'a.wasm', '-all'])
+        support.run_command(shared.WASM_REDUCE + ['a.wasm', '--command=%s b.wasm --fuzz-exec -all ' % shared.WASM_OPT[0], '-t', 'b.wasm', '-w', 'c.wasm', '--timeout=4'])
         expected = t + '.txt'
         support.run_command(shared.WASM_DIS + ['c.wasm', '-o', 'a.wat'])
         with open('a.wat') as seen:
diff --git a/src/tools/wasm-reduce.cpp b/src/tools/wasm-reduce.cpp
index 0332b4712..1d5164397 100644
--- a/src/tools/wasm-reduce.cpp
+++ b/src/tools/wasm-reduce.cpp
@@ -346,10 +346,14 @@ struct Reducer
 
   void loadWorking() {
     module = make_unique<Module>();
-    Module wasm;
     ModuleReader reader;
     reader.read(working, *module);
-    wasm.features = FeatureSet::All;
+    // If there is no features section, assume we may need them all (without
+    // this, a module with no features section but that uses e.g. atomics and
+    // bulk memory would not work).
+    if (!module->hasFeaturesSection) {
+      module->features = FeatureSet::All;
+    }
     builder = make_unique<Builder>(*module);
     setModule(module.get());
   }
diff --git a/test/reduce/atomics-and-bulk-memory.wast b/test/reduce/atomics-and-bulk-memory.wast
new file mode 100644
index 000000000..a5b31d4be
--- /dev/null
+++ b/test/reduce/atomics-and-bulk-memory.wast
@@ -0,0 +1,27 @@
+(module
+ (memory 1 1)
+ ;; this can be removed destructively
+ (data passive "some-data")
+ (func "foo" (result i32)
+  ;; this can be removed destructively
+  (memory.init 0
+   (i32.const 3)
+   (i32.const 3)
+   (i32.const 3))
+  (i32.atomic.store8
+   (i32.const 0)
+   ;; an add that can be optimized
+   (i32.add
+    (i32.const 97)
+    (i32.const 2)
+   )
+  )
+  ;; add some nops and blocks for reduction to remove
+  (nop)
+  (block (result i32)
+   (i32.atomic.load8_u
+    (i32.const 0)
+   )
+  )
+ )
+)
diff --git a/test/reduce/atomics-and-bulk-memory.wast.txt b/test/reduce/atomics-and-bulk-memory.wast.txt
new file mode 100644
index 000000000..ace3f57d9
--- /dev/null
+++ b/test/reduce/atomics-and-bulk-memory.wast.txt
@@ -0,0 +1,15 @@
+(module
+ (type $none_=>_i32 (func (result i32)))
+ (memory $0 1 1)
+ (export "foo" (func $0))
+ (func $0 (result i32)
+  (i32.atomic.store8
+   (i32.const 0)
+   (i32.const 99)
+  )
+  (i32.atomic.load8_u
+   (i32.const 0)
+  )
+ )
+)
+