X87: [builtins] Introduce proper Float64Log2 and Float64Log10 operators.

  port d9bf520a (r37035)

  original commit message:

BUG=

Review-Url: https://codereview.chromium.org/2100023002
Cr-Commit-Position: refs/heads/master@{#37268}

src/compiler/x87/code-generator-x87.cc

@@ -760,6 +760,12 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
     case kIeee754Float64Log1p:
       ASSEMBLE_IEEE754_UNOP(log1p);
       break;
+    case kIeee754Float64Log2:
+      ASSEMBLE_IEEE754_UNOP(log2);
+      break;
+    case kIeee754Float64Log10:
+      ASSEMBLE_IEEE754_UNOP(log10);
+      break;
     case kX87Add:
       if (HasImmediateInput(instr, 1)) {
         __ add(i.InputOperand(0), i.InputImmediate(1));