cm.push
Create function call stack frame
Creates a stack frame: store ra and 0 to 12 saved registers to the stack frame, optionally allocate additional stack space.
This instruction pushes (stores) the registers in reg_list to the memory below the stack pointer,
and then creates the stack frame by decrementing the stack pointer by stack_adj.
Restrictions on stack_adj:
-
it must be enough to store all of the listed registers
-
it must be a multiple of 16 (bytes):
-
for RV32 the allowed values are: 16, 32, 48, 64, 80, 96, 112
-
for RV64 the allowed values are: 16, 32, 48, 64, 80, 96, 112, 128, 144, 160
-
Execution
if (implemented?(ExtensionName::Zcmp) && (CSR[misa].C == 1'b0)) {
raise(ExceptionCode::IllegalInstruction, mode(), $encoding);
}
XReg size = xlen() / 8;
XReg nreg = (rlist == 15) ? 13 : (rlist - 3);
XReg stack_aligned_adj = (nreg * 4 + 15) & ~0xF;
XReg virtual_address_sp = X[2];
XReg virtual_address_new_sp = virtual_address_sp - stack_aligned_adj - spimm * 16;
XReg virtual_address_base = virtual_address_sp - (nreg * size);
write_memory_xlen_aligned(virtual_address_base + 0 * size, X[1], $encoding);
if (nreg > 1) {
write_memory_xlen_aligned(virtual_address_base + 1 * size, X[8], $encoding);
}
if (nreg > 2) {
write_memory_xlen_aligned(virtual_address_base + 2 * size, X[9], $encoding);
}
if (nreg > 3) {
write_memory_xlen_aligned(virtual_address_base + 3 * size, X[18], $encoding);
}
if (nreg > 4) {
write_memory_xlen_aligned(virtual_address_base + 4 * size, X[19], $encoding);
}
if (nreg > 5) {
write_memory_xlen_aligned(virtual_address_base + 5 * size, X[20], $encoding);
}
if (nreg > 6) {
write_memory_xlen_aligned(virtual_address_base + 6 * size, X[21], $encoding);
}
if (nreg > 7) {
write_memory_xlen_aligned(virtual_address_base + 7 * size, X[22], $encoding);
}
if (nreg > 8) {
write_memory_xlen_aligned(virtual_address_base + 8 * size, X[23], $encoding);
}
if (nreg > 9) {
write_memory_xlen_aligned(virtual_address_base + 9 * size, X[24], $encoding);
}
if (nreg > 10) {
write_memory_xlen_aligned(virtual_address_base + 10 * size, X[25], $encoding);
}
if (nreg > 11) {
write_memory_xlen_aligned(virtual_address_base + 11 * size, X[26], $encoding);
write_memory_xlen_aligned(virtual_address_base + 12 * size, X[27], $encoding);
}
X[2] = virtual_address_new_sp;Exceptions
This instruction may result in the following synchronous exceptions:
-
IllegalInstruction
-
LoadAccessFault
-
StoreAmoAccessFault
-
StoreAmoPageFault