cpyfm
Memory Copy Forward (Main)
Main loop of a hardware-accelerated memcpy (Forward direction).
Pseudocode Operation
No pseudocode available.
Encoding
Related
More in FEAT_MOPS
Reference
Instruction Forms
| Encoding | Instruction | ISA | Bit pattern | ||
|---|---|---|---|---|---|
| 0x19400400 | CPYFM [<Xd>]!, [<Xs>]!, <Xn>! | A64 | sz | 011 | 0 | 01 | 01 | 0 | Rs | 0000 | 01 | Rn | Rd |
Description
Memory Copy Forward-only. These instructions perform a memory copy. The prologue, main, and epilogue instructions are expected to be run in succession and to appear consecutively in memory: CPYFP, then CPYFM, and then CPYFE. CPYFP performs some preconditioning of the arguments suitable for using the CPYFM instruction, and performs an IMPLEMENTATION DEFINED amount of the memory copy. CPYFM performs an IMPLEMENTATION DEFINED amount of the memory copy. CPYFE performs the last part of the memory copy. The memory copy performed by these instructions is in the forward direction only, so the instructions are suitable for a memory copy only where there is no overlap between the source and destination locations, or where the source address is greater than the destination address. The architecture supports two algorithms for the memory copy: option A and option B. Which algorithm is used is IMPLEMENTATION DEFINED. After execution of CPYFP, option A (which results in encoding PSTATE.C = 0): After execution of CPYFP, option B (which results in encoding PSTATE.C = 1): For CPYFM, option A (encoded by PSTATE.C = 0), the format of the arguments is: For CPYFM, option B (encoded by PSTATE.C = 1), the format of the arguments is: For CPYFE, option A (encoded by PSTATE.C = 0), the format of the arguments is: For CPYFE, option B (encoded by PSTATE.C = 1), the format of the arguments is:
Operation
CheckMOPSEnabled();
CheckCPYConstrainedUnpredictable(memcpy.n, memcpy.d, memcpy.s);
constant integer N = MaxBlockSizeCopiedBytes();
bits(8*N) readdata;
memcpy.nzcv = PSTATE.<N,Z,C,V>;
memcpy.toaddress = X[memcpy.d, 64];
memcpy.fromaddress = X[memcpy.s, 64];
memcpy.cpysize = SInt(X[memcpy.n, 64]);
memcpy.implements_option_a = CPYFOptionA();
boolean rprivileged = if options<1> == '1' then AArch64.IsUnprivAccessPriv() else PSTATE.EL != EL0;
boolean wprivileged = if options<0> == '1' then AArch64.IsUnprivAccessPriv() else PSTATE.EL != EL0;
AccessDescriptor raccdesc = CreateAccDescMOPS(MemOp_LOAD, rprivileged, rnontemporal);
AccessDescriptor waccdesc = CreateAccDescMOPS(MemOp_STORE, wprivileged, wnontemporal);
if memcpy.stage == MOPSStage_Prologue then
if memcpy.cpysize<63> == '1' then memcpy.cpysize = 0x7FFFFFFFFFFFFFFF;
if memcpy.implements_option_a then
memcpy.nzcv = '0000';
// Copy in the forward direction offsets the arguments.
memcpy.toaddress = memcpy.toaddress + memcpy.cpysize;
memcpy.fromaddress = memcpy.fromaddress + memcpy.cpysize;
memcpy.cpysize = 0 - memcpy.cpysize;
else
memcpy.nzcv = '0010';
memcpy.stagecpysize = MemCpyStageSize(memcpy);
if memcpy.stage != MOPSStage_Prologue then
CheckMemCpyParams(memcpy, options);
integer copied;
boolean iswrite;
AddressDescriptor memaddrdesc;
PhysMemRetStatus memstatus;
memcpy.forward = TRUE;
boolean fault = FALSE;
integer B;
if memcpy.implements_option_a then
while memcpy.stagecpysize != 0 && !fault do
// IMP DEF selection of the block size that is worked on. While many
// implementations might make this constant, that is not assumed.
B = CPYSizeChoice(memcpy);
assert B <= -1 * memcpy.stagecpysize;
(copied, iswrite, memaddrdesc, memstatus) = MemCpyBytes(memcpy.toaddress + memcpy.cpysize, memcpy.fromaddress + memcpy.cpysize, memcpy.forward, B, raccdesc, waccdesc);
if copied != B then
fault = TRUE;
else
memcpy.cpysize = memcpy.cpysize + B;
memcpy.stagecpysize = memcpy.stagecpysize + B;
else
while memcpy.stagecpysize > 0 && !fault do
// IMP DEF selection of the block size that is worked on. While many
// implementations might make this constant, that is not assumed.
B = CPYSizeChoice(memcpy);
assert B <= memcpy.stagecpysize;
(copied, iswrite, memaddrdesc, memstatus) = MemCpyBytes(memcpy.toaddress, memcpy.fromaddress, memcpy.forward, B, raccdesc, waccdesc);
if copied != B then
fault = TRUE;
else
memcpy.fromaddress = memcpy.fromaddress + B;
memcpy.toaddress = memcpy.toaddress + B;
memcpy.cpysize = memcpy.cpysize - B;
memcpy.stagecpysize = memcpy.stagecpysize - B;
UpdateCpyRegisters(memcpy, fault, copied);
if fault then
if IsFault(memaddrdesc) then
AArch64.Abort(memaddrdesc.vaddress, memaddrdesc.fault);
if IsFault(memstatus) then
AccessDescriptor accdesc = if iswrite then waccdesc else raccdesc;
HandleExternalAbort(memstatus, iswrite, memaddrdesc, B, accdesc);
if memcpy.stage == MOPSStage_Prologue then
PSTATE.<N,Z,C,V> = memcpy.nzcv;