[Interpreter] Adds shift operators to interpreter

src/interpreter/interpreter.cc

Index: src/interpreter/interpreter.cc
diff --git a/src/interpreter/interpreter.cc b/src/interpreter/interpreter.cc
index 156d3b4e90cba5ce5bbe995ec46e976702feae83..a9de0a272948a2058dde70770f5c2c74ccec6455 100644
--- a/src/interpreter/interpreter.cc
+++ b/src/interpreter/interpreter.cc
@@ -375,6 +375,42 @@ void Interpreter::DoMod(compiler::InterpreterAssembler* assembler) {
 }
 
 
+// ShiftLeft <src>
+//
+// Left shifts accumulator by the count specified in register <src>.

[rmcilroy, 2015/10/08 14:53:07]

"accumulator" -> "the accumulator"

[oth, 2015/10/08 16:11:38]

Shouldn't it be Left shifts the register <src> by the value specified in the
accumulator? Same with the doc comments for ShiftRight and ShiftRightLogical.

+// accumulator is converted to a int32 and register <src> to uint32

[rmcilroy, 2015/10/08 14:53:07]

nit "accumulator" -> "The accumulator" (it's the start of a sentence)

[rmcilroy, 2015/10/08 14:53:07]

nit - a int32 -> an int32

+// before the operation. 5 lsb bits from register <src> are used as count.

[rmcilroy, 2015/10/08 14:53:07]

nit - move "." from after "count" to after "0x1F)"

+// i.e. accumulator << (<src> & 0x1F)
+void Interpreter::DoShiftLeft(compiler::InterpreterAssembler* assembler) {
+  DoBinaryOp(Runtime::kShiftLeft, assembler);
+}
+
+
+// ShiftRight <src>
+//
+// Right shifts accumulator by the count specified in register <src>.
+// Result is sign extended.

[rmcilroy, 2015/10/08 14:53:07]

Same comments here. Also, either bring the next sentence onto this line, or add
a blank comment line if you want to make a paragraph.

+// accumulator is converted to a int32 and register <src> to uint32
+// before the operation. 5 lsb bits from register <src> are used as count.
+// i.e. accumulator >> (<src> & 0x1F)
+void Interpreter::DoShiftRight(compiler::InterpreterAssembler* assembler) {
+  DoBinaryOp(Runtime::kShiftRight, assembler);
+}
+
+
+// ShiftRightLogical <src>
+//
+// Right Shifts accumulator by the count specified in register <src>.
+// Result is zero-filled.

[rmcilroy, 2015/10/08 14:53:07]

ditto

+// accumulator and register <src> are converted to uint32 before the operation
+// lsb bits from register <src> are used as count.
+// i.e. accumulator >> (<src> & 0x1F)
+void Interpreter::DoShiftRightLogical(
+    compiler::InterpreterAssembler* assembler) {
+  DoBinaryOp(Runtime::kShiftRightLogical, assembler);
+}
+
+
 // LogicalNot
 //
 // Perform logical-not on the accumulator, first casting the