X19
alias W19architectural number 19Callee-saved (platform register)
X1964-bit view
X only
shared with W19
W1932-bit view
bits 31:0 of X19
write
Writing W19 does not simply deposit 32 bits. Bits 63:32 of X19 are reset to zero as a side effect, so a W write always clears the upper half. This is the reason W19 and X19 can never hold unrelated values at the same time.
Notes
First of the ten callee-saved registers. A callee that clobbers it must save and restore it.