Implement shifting with a differently-sized integer

compiler.go

@@ -1530,6 +1530,15 @@ func (c *Compiler) parseBinOp(frame *Frame, binop *ssa.BinOp) (llvm.Value, error
 		return c.builder.CreateOr(x, y, ""), nil
 	case token.XOR: // ^
 		return c.builder.CreateXor(x, y, ""), nil
+	case token.SHL, token.SHR:
+		sizeX := c.targetData.TypeAllocSize(x.Type())
+		sizeY := c.targetData.TypeAllocSize(y.Type())
+		if sizeX > sizeY {
+			// x and y must have equal sizes, make Y bigger in this case.
+			// y is unsigned, this has been checked by the Go type checker.
+			y = c.builder.CreateZExt(y, x.Type(), "")
+		}
+		switch binop.Op {
 		case token.SHL: // <<
 			return c.builder.CreateShl(x, y, ""), nil
 		case token.SHR: // >>
@@ -1538,6 +1547,9 @@ func (c *Compiler) parseBinOp(frame *Frame, binop *ssa.BinOp) (llvm.Value, error
 			} else {
 				return c.builder.CreateLShr(x, y, ""), nil
 			}
+		default:
+			panic("unreachable")
+		}
 	case token.AND_NOT: // &^
 		// Go specific. Calculate "and not" with x & (~y)
 		inv := c.builder.CreateNot(y, "") // ~y