[wasm] asm.js. Adds support for clz32 in asm.js.

BUG= https://bugs.chromium.org/p/v8/issues/detail?id=4203

Review-Url: https://codereview.chromium.org/2200213002
Cr-Commit-Position: refs/heads/master@{#38259}

src/asmjs/asm-typer.cc

@@ -178,6 +178,9 @@ void AsmTyper::InitializeStdlib() {
   s2s->AsFunctionType()->AddArgument(s);
 
   auto* i = AsmType::Int();
+  auto* i2s = AsmType::Function(zone_, s);
+  i2s->AsFunctionType()->AddArgument(i);
+
   auto* ii2s = AsmType::Function(zone_, s);
   ii2s->AsFunctionType()->AddArgument(i);
   ii2s->AsFunctionType()->AddArgument(i);
@@ -248,6 +251,10 @@ void AsmTyper::InitializeStdlib() {
       {"SQRT1_2", kMathSQRT1_2, d},
       {"imul", kMathImul, ii2s},
       {"abs", kMathAbs, abs},
+      // NOTE: clz32 should return fixnum. The current typer can only return
+      // Signed, Float, or Double, so it returns Signed in our version of
+      // asm.js.
+      {"clz32", kMathClz32, i2s},
       {"ceil", kMathCeil, ceil},
       {"floor", kMathFloor, floor},
       {"fround", kMathFround, fround},

src/asmjs/asm-typer.h

@@ -47,6 +47,7 @@ class AsmTyper final {
     kMathFloor,
     kMathSqrt,
     kMathAbs,
+    kMathClz32,
     kMathMin,
     kMathMax,
     kMathAtan2,

src/asmjs/asm-wasm-builder.cc

@@ -1085,6 +1085,12 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
         }
         break;
       }
+      case AsmTyper::kMathClz32: {
+        VisitCallArgs(call);
+        DCHECK(call_type == kAstI32);
+        current_function_builder_->Emit(kExprI32Clz);
+        break;
+      }
       case AsmTyper::kMathAbs: {
         if (call_type == kAstI32) {
           uint32_t tmp = current_function_builder_->AddLocal(kAstI32);

test/mjsunit/wasm/asm-wasm-stdlib.js

@@ -50,6 +50,7 @@
     "use asm";
 
     var StdlibMathCeil = stdlib.Math.ceil;
+    var StdlibMathClz32 = stdlib.Math.clz32;
     var StdlibMathFloor = stdlib.Math.floor;
     var StdlibMathSqrt = stdlib.Math.sqrt;
     var StdlibMathAbs = stdlib.Math.abs;
@@ -106,6 +107,7 @@
       if (!(deltaEqual(+StdlibMathTan(0.2), 0.20271003550867250)|0)) return 0;
       if (!(deltaEqual(+StdlibMathExp(0.2), 1.2214027581601699)|0)) return 0;
       if (!(deltaEqual(+StdlibMathLog(0.2), -1.6094379124341003)|0)) return 0;
+      if ((StdlibMathClz32(134217728)|0) != 4) return 0;
 
       if ((StdlibMathImul(6, 7)|0) != 42) return 0;
       if (!(deltaEqual(+StdlibMathAtan2(6.0, 7.0), 0.7086262721276703)|0))