X7
alias W7architectural number 7Argument 7
X764-bit view
X only
shared with W7
W732-bit view
bits 31:0 of X7
write
Writing W7 does not simply deposit 32 bits. Bits 63:32 of X7 are reset to zero as a side effect, so a W write always clears the upper half. This is the reason W7 and X7 can never hold unrelated values at the same time.
Notes
Last of the eight argument registers, and the first beyond which arguments go on the stack.