Descend to nested lvalue for assign, binAssign and address-of expressions.

[kinke]

Thereby enabling nested assign/binAssign expressions in left-hand-sides of assign/binAssign expressions as well as taking the address of assign/binAssign expressions (e.g., required to return assign/binAssign expressions by reference).

import core.stdc.stdio;

ref int foo()
{
    static int a;
    return ++a *= 5;
}

void main()
{
    int a = foo();
    printf("%d\n", a);

    int b = 0;
    ((++b *= 5) *= 2) += 3;
    printf("%d\n", b);

    b = 0;
    ((++b *= 5) *= 2) += ++b * b;
    printf("%d\n", b);

    b = 0;
    ((++b *= 5) *= 2) += ++b * (b -= 6);
    printf("%d\n", b);

    b = 0;
    (((b = 1) *= 5) *= 2) = b - 1;
    printf("%d\n", b);
}

yields

5
13
131
65
9

[kinke]

This 2.067 front-end change has a nice effect:

• Above foo() function - LDC2 0.15.2:

define i32* @_D4incr3fooFNcZi() #0 {
  %__assignop1 = alloca i32*, align 8
  %1 = load i32* @_D4incr3fooFNcZ1ai
  %2 = add i32 %1, 1
  store i32 %2, i32* @_D4incr3fooFNcZ1ai
  store i32* @_D4incr3fooFNcZ1ai, i32** %__assignop1
  %3 = load i32** %__assignop1
  %4 = load i32* %3
  %5 = mul i32 %4, 5
  store i32 %5, i32* %3
  %6 = load i32** %__assignop1
  ret i32* %6
}

master:

define i32* @_D4incr3fooFNcZi() #0 {
  %1 = load i32* @_D4incr3fooFNcZ1ai
  %2 = add i32 %1, 1
  store i32 %2, i32* @_D4incr3fooFNcZ1ai
  %3 = mul i32 %2, 5
  store i32 %3, i32* @_D4incr3fooFNcZ1ai
  ret i32* @_D4incr3fooFNcZ1ai
}

• First b test - 0.15.2:

  %__assignop3 = alloca i32*, align 8
  %__assignop2 = alloca i32*, align 8
  ...
  store i32 0, i32* %b
  %4 = load i32* %b
  %5 = load i32* %b
  %6 = add i32 %5, 1
  store i32 %6, i32* %b
  store i32* %b, i32** %__assignop2
  %7 = load i32** %__assignop2
  %8 = load i32* %7
  %9 = mul i32 %8, 5
  store i32 %9, i32* %7
  %10 = load i32** %__assignop2
  store i32* %10, i32** %__assignop3
  %11 = load i32** %__assignop3
  %12 = load i32* %11
  %13 = mul i32 %12, 2
  store i32 %13, i32* %11
  %14 = load i32** %__assignop3
  %15 = load i32* %14
  %16 = add i32 %15, 3
  store i32 %16, i32* %14

master:

  store i32 0, i32* %b
  %4 = load i32* %b
  %5 = load i32* %b
  %6 = add i32 %5, 1
  store i32 %6, i32* %b
  %7 = mul i32 %6, 5
  store i32 %7, i32* %b
  %8 = mul i32 %7, 2
  store i32 %8, i32* %b
  %9 = add i32 %8, 3
  store i32 %9, i32* %b
  %10 = load i32* %b