do not combine a load/store offset with a constant pointer if it would wrap a negative value to a positive one, as trapping is tricky

Author: kripken

auto_update_tests.py

@@ -93,7 +93,7 @@
     print '..', t
     binary = '.wasm' in t
     passname = os.path.basename(t).replace('.wast', '').replace('.wasm', '')
-    opts = ['-' + passname] if passname.startswith('O') else ['--' + p for p in passname.split('_')]
+    opts = [('--' + p if not p.startswith('O') else '-' + p) for p in passname.split('_')]
     t = os.path.join('test', 'passes', t)
     actual = ''
     for module, asserts in split_wast(t):

check.py

@@ -78,7 +78,7 @@
     print '..', t
     binary = '.wasm' in t
     passname = os.path.basename(t).replace('.wast', '').replace('.wasm', '')
-    opts = ['-' + passname] if passname.startswith('O') else ['--' + p for p in passname.split('_')]
+    opts = [('--' + p if not p.startswith('O') else '-' + p) for p in passname.split('_')]
     t = os.path.join(options.binaryen_test, 'passes', t)
     actual = ''
     for module, asserts in split_wast(t):

src/passes/OptimizeInstructions.cpp

@@ -908,8 +908,15 @@ struct OptimizeInstructions : public WalkerPass<PostWalker<OptimizeInstructions,
     // it's better to do the opposite for gzip purposes as well as for readability.
     auto* last = ptr->dynCast<Const>();
     if (last) {
-      last->value = Literal(int32_t(last->value.geti32() + offset));
-      offset = 0;
+      // don't do this if it would wrap the pointer
+      uint64_t value64 = last->value.geti32();
+      uint64_t offset64 = offset;
+      if (value64 <= std::numeric_limits<int32_t>::max() &&
+          offset64 <= std::numeric_limits<int32_t>::max() &&
+          value64 + offset64 <= std::numeric_limits<int32_t>::max()) {
+        last->value = Literal(int32_t(value64 + offset64));
+        offset = 0;
+      }
     }
   }
 

test/passes/fuzz-exec_O.txt

@@ -0,0 +1,25 @@
+[fuzz-exec] 2 results noted
+(module
+ (type $0 (func (result i64)))
+ (type $1 (func (result i32)))
+ (memory $0 1 1)
+ (export "func_0" (func $func_0))
+ (export "func_1" (func $func_1))
+ (func $func_0 (type $0) (result i64)
+  (block $label$0 (result i64)
+   (br_if $label$0
+    (i64.const 1234)
+    (i32.load16_s offset=22 align=1
+     (i32.const -1)
+    )
+   )
+  )
+ )
+ (func $func_1 (type $1) (result i32)
+  (i32.load16_s offset=22 align=1
+   (i32.const -1)
+  )
+ )
+)
+[fuzz-exec] 2 results noted
+[fuzz-exec] results match

test/passes/fuzz-exec_O.wast

@@ -0,0 +1,23 @@
+(module
+ (memory $0 1 1)
+ (export "func_0" (func $func_0))
+ (export "func_1" (func $func_1))
+ (func $func_0 (result i64)
+  (block $label$0 (result i64)
+   (loop $label$1 (result i64)
+    (br_if $label$0
+     (i64.const 1234)
+     (i32.load16_s offset=22 align=1
+      (i32.const -1)
+     )
+    )
+   )
+  )
+ )
+ (func $func_1 (result i32)
+  (i32.load16_s offset=22 align=1
+   (i32.const -1)
+  )
+ )
+)
+

test/passes/optimize-instructions.txt

@@ -462,16 +462,16 @@
    (i32.const 4)
    (get_local $0)
   )
-  (i32.store
-   (i32.const 0)
+  (i32.store offset=2
+   (i32.const -2)
    (get_local $0)
   )
   (i32.store
    (i32.const 25)
    (get_local $0)
   )
-  (i32.store
-   (i32.const -23)
+  (i32.store offset=2
+   (i32.const -25)
    (get_local $0)
   )
   (drop