[wasm][refactor] Simplify/unify parts of the function decoder

Changes:
- Remove TypeCheckBranchResult. Change TypeCheckBranch() to return bool.
  Refactor call sites to reflect this (decouple current code
  reachability check from type check).
- Unify TypeCheckBranch(), TypeCheckFallthrough(), and the type-checking
  part of Return() into TypeCheckStackAgainstMerge().
- Make sure all TypeCheck* functions are only called within VALIDATE.
- In graph-builder-interface, rename end_env -> merge_env to reflect
  its function for loops.
- Change expected error messages in some tests.

Change-Id: I857edc18db9c2454ad12d539ffe7a10e96367710
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2839560Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74100}

src/wasm/graph-builder-interface.cc

@@ -95,7 +95,7 @@ class WasmGraphBuildingInterface {
   };
 
   struct Control : public ControlBase<Value, validate> {
-    SsaEnv* end_env = nullptr;    // end environment for the construct.
+    SsaEnv* merge_env = nullptr;  // merge environment for the construct.
     SsaEnv* false_env = nullptr;  // false environment (only for if).
     TryInfo* try_info = nullptr;  // information about try statements.
     int32_t previous_catch = -1;  // previous Control with a catch.
@@ -154,15 +154,15 @@ class WasmGraphBuildingInterface {
 
   void Block(FullDecoder* decoder, Control* block) {
     // The branch environment is the outer environment.
-    block->end_env = ssa_env_;
+    block->merge_env = ssa_env_;
     SetEnv(Steal(decoder->zone(), ssa_env_));
   }
 
   void Loop(FullDecoder* decoder, Control* block) {
-    SsaEnv* finish_try_env = Steal(decoder->zone(), ssa_env_);
-    block->end_env = finish_try_env;
-    SetEnv(finish_try_env);
-    // The continue environment is the inner environment.
+    // This is the merge environment at the beginning of the loop.
+    SsaEnv* merge_env = Steal(decoder->zone(), ssa_env_);
+    block->merge_env = merge_env;
+    SetEnv(merge_env);
 
     ssa_env_->state = SsaEnv::kMerged;
 
@@ -214,15 +214,15 @@ class WasmGraphBuildingInterface {
                                             control());
     }
 
+    // Now we setup a new environment for the inside of the loop.
     SetEnv(Split(decoder->zone(), ssa_env_));
     builder_->StackCheck(decoder->position());
-
     ssa_env_->SetNotMerged();
-    if (!decoder->ok()) return;
+
     // Wrap input merge into phis.
     for (uint32_t i = 0; i < block->start_merge.arity; ++i) {
       Value& val = block->start_merge[i];
-      TFNode* inputs[] = {val.node, block->end_env->control};
+      TFNode* inputs[] = {val.node, block->merge_env->control};
       val.node = builder_->Phi(val.type, 1, inputs);
     }
   }
@@ -236,7 +236,7 @@ class WasmGraphBuildingInterface {
     SsaEnv* try_env = Steal(decoder->zone(), outer_env);
     SetEnv(try_env);
     TryInfo* try_info = decoder->zone()->New<TryInfo>(catch_env);
-    block->end_env = outer_env;
+    block->merge_env = outer_env;
     block->try_info = try_info;
   }
 
@@ -244,12 +244,12 @@ class WasmGraphBuildingInterface {
     TFNode* if_true = nullptr;
     TFNode* if_false = nullptr;
     builder_->BranchNoHint(cond.node, &if_true, &if_false);
-    SsaEnv* end_env = ssa_env_;
+    SsaEnv* merge_env = ssa_env_;
     SsaEnv* false_env = Split(decoder->zone(), ssa_env_);
     false_env->control = if_false;
     SsaEnv* true_env = Steal(decoder->zone(), ssa_env_);
     true_env->control = if_true;
-    if_block->end_env = end_env;
+    if_block->merge_env = merge_env;
     if_block->false_env = false_env;
     SetEnv(true_env);
   }
@@ -290,7 +290,7 @@ class WasmGraphBuildingInterface {
       MergeValuesInto(decoder, block, &block->end_merge, values);
     }
     // Now continue with the merged environment.
-    SetEnv(block->end_env);
+    SetEnv(block->merge_env);
   }
 
   void UnOp(FullDecoder* decoder, WasmOpcode opcode, const Value& value,
@@ -1197,7 +1197,7 @@ class WasmGraphBuildingInterface {
                        Value* values) {
     DCHECK(merge == &c->start_merge || merge == &c->end_merge);
 
-    SsaEnv* target = c->end_env;
+    SsaEnv* target = c->merge_env;
     // This has to be computed before calling Goto().
     const bool first = target->state == SsaEnv::kUnreachable;
 

test/message/fail/wasm-async-compile-fail.out

-*%(basename)s:9: CompileError: WebAssembly.compile(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+*%(basename)s:9: CompileError: WebAssembly.compile(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 let rethrow = e => setTimeout(_ => {throw e}, 0);
                                     ^
-CompileError: WebAssembly.compile(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+CompileError: WebAssembly.compile(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 

test/message/fail/wasm-async-instantiate-fail.out

-*%(basename)s:9: CompileError: WebAssembly.instantiate(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+*%(basename)s:9: CompileError: WebAssembly.instantiate(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 let rethrow = e => setTimeout(_ => {throw e}, 0);
                                     ^
-CompileError: WebAssembly.instantiate(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+CompileError: WebAssembly.instantiate(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 

test/message/fail/wasm-streaming-compile-fail.out

-*%(basename)s:11: CompileError: WebAssembly.compileStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+*%(basename)s:11: CompileError: WebAssembly.compileStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 let rethrow = e => setTimeout(_ => {throw e}, 0);
                                     ^
-CompileError: WebAssembly.compileStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+CompileError: WebAssembly.compileStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 

test/message/fail/wasm-streaming-instantiate-fail.out

-*%(basename)s:11: CompileError: WebAssembly.instantiateStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+*%(basename)s:11: CompileError: WebAssembly.instantiateStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 let rethrow = e => setTimeout(_ => {throw e}, 0);
                                     ^
-CompileError: WebAssembly.instantiateStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+CompileError: WebAssembly.instantiateStreaming(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 

test/message/fail/wasm-sync-compile-fail.out

-*%(basename)s:9: CompileError: WebAssembly.Module(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+*%(basename)s:9: CompileError: WebAssembly.Module(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
 new WebAssembly.Module(builder.toBuffer());
 ^
-CompileError: WebAssembly.Module(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru to @1, found 0 @+24
+CompileError: WebAssembly.Module(): Compiling function #0:"f" failed: expected 1 elements on the stack for fallthru, found 0 @+24
     at *%(basename)s:9:1
 

test/mjsunit/regress/wasm/regress-1046472.js

@@ -29,5 +29,5 @@ kExprEnd,   // @21
   assertThrows(
       () => {builder.toModule()}, WebAssembly.CompileError,
       'WebAssembly.Module(): Compiling function #0:\"main\" failed: ' +
-      'type error in merge[0] (expected f32, got i32) @+57');
+      'type error in branch[0] (expected f32, got i32) @+57');
 })();

test/mjsunit/wasm/async-compile.js

@@ -67,7 +67,7 @@ assertPromiseResult(async function badFunctionInTheMiddle() {
   await assertCompileError(
       buffer,
       'Compiling function #10:\"bad\" failed: ' +
-          'expected 1 elements on the stack for fallthru to @1, found 0 @+94');
+          'expected 1 elements on the stack for fallthru, found 0 @+94');
 }());
 
 assertPromiseResult(async function importWithoutCode() {

test/mjsunit/wasm/compilation-hints-async-compilation.js

@@ -35,7 +35,7 @@ load('test/mjsunit/wasm/wasm-module-builder.js');
   assertPromiseResult(WebAssembly.compile(bytes)
     .then(assertUnreachable,
           error => assertEquals("WebAssembly.compile(): type error in " +
-          "merge[0] (expected i32, got i64) @+56", error.message)));
+          "fallthru[0] (expected i32, got i64) @+56", error.message)));
 })();
 
 (function testCompileEmptyModule() {

test/mjsunit/wasm/compilation-hints-sync-compilation.js

@@ -33,7 +33,7 @@ load('test/mjsunit/wasm/wasm-module-builder.js');
   assertThrows(() => builder.toModule(),
     WebAssembly.CompileError,
     "WebAssembly.Module(): Compiling function #0:\"id\" failed: type error " +
-    "in merge[0] (expected i32, got i64) @+56");
+    "in fallthru[0] (expected i32, got i64) @+56");
 })();
 
 (function testCompileEmptyModule() {

test/unittests/wasm/function-body-decoder-unittest.cc

@@ -3841,7 +3841,7 @@ TEST_F(FunctionBodyDecoderTest, BrOnNull) {
                               WASM_I32V(0), kExprSelectWithType, 1,
                               WASM_REF_TYPE(reps[0]))},
                 kAppendEnd,
-                "expected 1 elements on the stack for br to @1, found 0");
+                "expected 1 elements on the stack for branch, found 0");
 }
 
 TEST_F(FunctionBodyDecoderTest, GCStruct) {
@@ -3880,8 +3880,7 @@ TEST_F(FunctionBodyDecoderTest, GCStruct) {
       &sig_r_v,
       {WASM_STRUCT_NEW_WITH_RTT(struct_type_index, WASM_I32V(0), WASM_I32V(1),
                                 WASM_RTT_CANON(struct_type_index))},
-      kAppendEnd,
-      "expected 1 elements on the stack for fallthru to @1, found 2");
+      kAppendEnd, "expected 1 elements on the stack for fallthru, found 2");
   // Mistyped arguments.
   ExpectFailure(&sig_v_r,
                 {WASM_STRUCT_NEW_WITH_RTT(struct_type_index, WASM_LOCAL_GET(0),
@@ -3927,7 +3926,7 @@ TEST_F(FunctionBodyDecoderTest, GCStruct) {
   ExpectFailure(
       &sig_f_r,
       {WASM_STRUCT_GET(struct_type_index, field_index, WASM_LOCAL_GET(0))},
-      kAppendEnd, "type error in merge[0] (expected f32, got i32)");
+      kAppendEnd, "type error in fallthru[0] (expected f32, got i32)");
 
   /** struct.set **/
   ExpectValidates(&sig_v_r, {WASM_STRUCT_SET(struct_type_index, field_index,
@@ -3953,7 +3952,7 @@ TEST_F(FunctionBodyDecoderTest, GCStruct) {
                 {WASM_STRUCT_SET(struct_type_index, field_index,
                                  WASM_LOCAL_GET(0), WASM_I32V(0))},
                 kAppendEnd,
-                "expected 1 elements on the stack for fallthru to @1, found 0");
+                "expected 1 elements on the stack for fallthru, found 0");
   // Setting immutable field.
   ExpectFailure(
       sigs.v_v(),
@@ -4063,7 +4062,7 @@ TEST_F(FunctionBodyDecoderTest, GCArray) {
   ExpectFailure(
       &sig_f_r,
       {WASM_ARRAY_GET(array_type_index, WASM_LOCAL_GET(0), WASM_I32V(5))},
-      kAppendEnd, "type error in merge[0] (expected f32, got funcref)");
+      kAppendEnd, "type error in fallthru[0] (expected f32, got funcref)");
 
   // array.get_s/u fail.
   ExpectFailure(
@@ -4112,7 +4111,8 @@ TEST_F(FunctionBodyDecoderTest, GCArray) {
                   {WASM_ARRAY_LEN(array_type_index, WASM_LOCAL_GET(0))});
   // Wrong return type.
   ExpectFailure(&sig_f_r, {WASM_ARRAY_LEN(array_type_index, WASM_LOCAL_GET(0))},
-                kAppendEnd, "type error in merge[0] (expected f32, got i32)");
+                kAppendEnd,
+                "type error in fallthru[0] (expected f32, got i32)");
   // Non-array type index.
   ExpectFailure(&sig_i_r,
                 {WASM_ARRAY_LEN(struct_type_index, WASM_LOCAL_GET(0))},
@@ -4234,7 +4234,7 @@ TEST_F(FunctionBodyDecoderTest, RttCanon) {
     ValueType rtt2 = ValueType::Rtt(type_index, 1);
     FunctionSig sig2(1, 0, &rtt2);
     ExpectFailure(&sig2, {WASM_RTT_CANON(type_index)}, kAppendEnd,
-                  "type error in merge[0]");
+                  "type error in fallthru[0]");
   }
 }