[wasm] Enable wasm loop analysis by default.

Loop analysis results in smaller graphs (fewer phis), thus faster
compilation time and better code.

R=ahaas@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1836223002

Cr-Commit-Position: refs/heads/master@{#35103}

src/compiler/wasm-compiler.cc

@@ -352,8 +352,7 @@ Node* WasmGraphBuilder::Merge(unsigned count, Node** controls) {
 Node* WasmGraphBuilder::Phi(wasm::LocalType type, unsigned count, Node** vals,
                             Node* control) {
   DCHECK(IrOpcode::IsMergeOpcode(control->opcode()));
-  Node** buf = Realloc(vals, count);
-  buf = Realloc(buf, count + 1);
+  Node** buf = Realloc(vals, count, count + 1);
   buf[count] = control;
   return graph()->NewNode(jsgraph()->common()->Phi(type, count), count + 1,
                           buf);
@@ -363,8 +362,7 @@ Node* WasmGraphBuilder::Phi(wasm::LocalType type, unsigned count, Node** vals,
 Node* WasmGraphBuilder::EffectPhi(unsigned count, Node** effects,
                                   Node* control) {
   DCHECK(IrOpcode::IsMergeOpcode(control->opcode()));
-  Node** buf = Realloc(effects, count);
-  buf = Realloc(buf, count + 1);
+  Node** buf = Realloc(effects, count, count + 1);
   buf[count] = control;
   return graph()->NewNode(jsgraph()->common()->EffectPhi(count), count + 1,
                           buf);
@@ -976,8 +974,7 @@ Node* WasmGraphBuilder::Return(unsigned count, Node** vals) {
     count = 1;
   }
 
-  Node** buf = Realloc(vals, count);
-  buf = Realloc(buf, count + 2);
+  Node** buf = Realloc(vals, count, count + 2);
   buf[count] = *effect_;
   buf[count + 1] = *control_;
   Node* ret = graph()->NewNode(jsgraph()->common()->Return(), count + 2, vals);
@@ -1569,7 +1566,7 @@ Node* WasmGraphBuilder::BuildCFuncInstruction(ExternalReference ref,
                               *control_);
 
   Node* function = graph()->NewNode(jsgraph()->common()->ExternalConstant(ref));
-  Node** args = Buffer(4);
+  Node** args = Buffer(5);
   args[0] = function;
   args[1] = stack_slot_param0;
   int input_count = 1;
@@ -1582,7 +1579,6 @@ Node* WasmGraphBuilder::BuildCFuncInstruction(ExternalReference ref,
     *effect_ = graph()->NewNode(store_op1, stack_slot_param1,
                                 jsgraph()->Int32Constant(0), input1, *effect_,
                                 *control_);
-    args = Realloc(args, 5);
     args[2] = stack_slot_param1;
     ++input_count;
   }
@@ -1855,7 +1851,7 @@ Node* WasmGraphBuilder::BuildCCall(MachineSignature* sig, Node** args) {
   const size_t count = 1 + params + extra;
 
   // Reallocate the buffer to make space for extra inputs.
-  args = Realloc(args, count);
+  args = Realloc(args, 1 + params, count);
 
   // Add effect and control inputs.
   args[params + 1] = *effect_;
@@ -1876,7 +1872,7 @@ Node* WasmGraphBuilder::BuildWasmCall(wasm::FunctionSig* sig, Node** args) {
   const size_t count = 1 + params + extra;
 
   // Reallocate the buffer to make space for extra inputs.
-  args = Realloc(args, count);
+  args = Realloc(args, 1 + params, count);
 
   // Add effect and control inputs.
   args[params + 1] = *effect_;

src/compiler/wasm-compiler.h

@@ -232,9 +232,9 @@ class WasmGraphBuilder {
   Node* BuildDiv64Call(Node* left, Node* right, ExternalReference ref,
                        MachineType result_type, int trap_zero);
 
-  Node** Realloc(Node** buffer, size_t count) {
-    Node** buf = Buffer(count);
-    if (buf != buffer) memcpy(buf, buffer, count * sizeof(Node*));
+  Node** Realloc(Node** buffer, size_t old_count, size_t new_count) {
+    Node** buf = Buffer(new_count);
+    if (buf != buffer) memcpy(buf, buffer, old_count * sizeof(Node*));
     return buf;
   }
 };

src/flag-definitions.h

@@ -468,7 +468,7 @@ DEFINE_INT(trace_wasm_ast_end, 0, "end function for WASM AST trace (exclusive)")
 DEFINE_INT(skip_compiling_wasm_funcs, 0, "start compiling at function N")
 DEFINE_BOOL(wasm_break_on_decoder_error, false,
             "debug break when wasm decoder encounters an error")
-DEFINE_BOOL(wasm_loop_assignment_analysis, false,
+DEFINE_BOOL(wasm_loop_assignment_analysis, true,
             "perform loop assignment analysis for WASM")
 
 DEFINE_BOOL(enable_simd_asmjs, false, "enable SIMD.js in asm.js stdlib")