Specification: assignment to $X. If X < rG, registers $0 to $X - 1 are pushed to the register stack. If $X is a marginal register, it is automatically made local as in an Finally, the value X is pushed on the register stack.
If X ≥ rG, registers $0 to $rL-1 are pushed to the register stack Finally, the value rL is pushed on the register stack and rL ← 0.
Further:
| rJ | ← @ + 4 |
| @ | ← @ + 4YZ (PUSHJ) or |
| @ | ← @ + 4(YZ - 216) (PUSHJB) or |
| @ | ← $Y + $Z (PUSHGO) or |
| @ | ← $Y + Z (PUSHGOI) |
The PUSHJ-Operation of x + 1 registers to the register stack
S[0],…,S[τ - 1] entails the following:
| S[τ] | ← $0 |
| S[τ + 1] | ← $1 |
| … | |
| S[τ + x - 1] | ← $(X - 1), |
| S[τ + x] | ← x, |
| τ | ← τ + x + 1, |
| $0 | ← $(x + 1) |
| … | |
| $(rL - x - 2) | ← $(rL - 1), |
| rL | ← rL - x - 1. |
Timing:
PUSHJ: 1υ
PUSHGO: 3υ
Description:
The PUSHJ and PUSHGO instructions are used to link subroutines. The only difference between the two is the computation of the target address. PUSHJ uses a 16-bit relative address, like branch instructions, while PUSHGO uses an absolute address $Y+$Z (or $Y+Z) like the GO instruction.
See also: