X30
alias W30architectural number 30Link register (LR)
X3064-bit view
X only
shared with W30
W3032-bit view
bits 31:0 of X30
write
Writing W30 does not simply deposit 32 bits. Bits 63:32 of X30 are reset to zero as a side effect, so a W write always clears the upper half. This is the reason W30 and X30 can never hold unrelated values at the same time.
Notes
Written by BL and BLR with the return address. A leaf function never needs to save it; any function that makes a further call must spill it to the stack.