gas: Optimize variable reference on assembly

We were moving the stack data for variable reference to another stack
position ending up with two pointer to the same value.

    // a: i32 = 1;
    mov $1, -8(%rbp)
    // b: i32 = a;
    mov -8(%rbp), %rax
    mov %rax, -24(%rbp)
    mov -24(%rbp), %rax
    mov %rax, -16(%rbp)

After this changes, we wont create a new temp space on stack if we don't
need it. See bellow the example after the optimization:

    // a: i32 = 1;
    mov $1, -8(%rbp)
    // b: i32 = a;
    mov -8(%rbp), %rax
    mov %rax, -16(%rbp)

Signed-off-by: Johnny Richard <johnny@johnnyrichard.com>
Co-authored-by: Carlos Maniero <carlosmaniero@gmail.com>

1 files changed, 2 insertions, 1 deletions

diff --git a/examples/variables.pipa b/examples/variables.pipa
index 9c395ce..25cbd59 100644
--- a/examples/variables.pipa
+++ b/examples/variables.pipa
@@ -3,5 +3,6 @@ main(): i32 {
   b: i32 = 32;
   c: i32 = 2 * (b + a);
   d: i32 = (c - 33) + 1;
-  return d / 2;
+  e: i32 = d;
+  return e / 2;
 }