Cherry Mui c10b980220 cmd/compile: restore tail call for method wrappers ... For certain type of method wrappers we used to generate a tail call. That was disabled in CL 307234 when register ABI is used, because with the current IR it was difficult to generate a tail call with the arguments in the right places. The problem was that the IR does not contain a CALL-like node with arguments; instead, it contains an OAS node that adjusts the receiver, than an OTAILCALL node that just contains the target, but no argument (with the assumption that the OAS node will put the adjusted receiver in the right place). With register ABI, putting arguments in registers are done in SSA. The assignment (OAS) doesn't put the receiver in register. This CL changes the IR of a tail call to take an actual OCALL node. Specifically, a tail call is represented as OTAILCALL (OCALL target args...) This way, the call target and args are connected through the OCALL node. So the call can be analyzed in SSA and the args can be passed in the right places. (Alternatively, we could have OTAILCALL node directly take the target and the args, without the OCALL node. Using an OCALL node is convenient as there are existing code that processes OCALL nodes which do not need to be changed. Also, a tail call is similar to ORETURN (OCALL target args...), except it doesn't preserve the frame. I did the former but I'm open to change.) The SSA representation is similar. Previously, the IR lowers to a Store the receiver then a BlockRetJmp which jumps to the target (without putting the arg in register). Now we use a TailCall op, which takes the target and the args. The call expansion pass and the register allocator handles TailCall pretty much like a StaticCall, and it will do the right ABI analysis and put the args in the right places. (Args other than the receiver are already in the right places. For register args it generates no code for them. For stack args currently it generates a self copy. I'll work on optimize that out.) BlockRetJmp is still used, signaling it is a tail call. The actual call is made in the TailCall op so BlockRetJmp generates no code (we could use BlockExit if we like). This slightly reduces binary size: old new cmd/go 14003088 13953936 cmd/link 6275552 6271456 Change-Id: I2d16d8d419fe1f17554916d317427383e17e27f0 Reviewed-on: https://go-review.googlesource.com/c/go/+/350145 Trust: Cherry Mui <cherryyz@google.com> Run-TryBot: Cherry Mui <cherryyz@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com> Reviewed-by: David Chase <drchase@google.com>		2021-09-17 22:59:44 +00:00
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bad_internal_offsets.go
bad_select_crash.go
convF_criteria.go
convF_criteria.out
convT64_criteria.go
convT64_criteria.out
defer_aggregate.go
defer_recover_results.go
double_nested_addressed_struct.go
double_nested_struct.go
f_ret_z_not.go
f_ret_z_not.out
fibish_closure.go
fibish_closure.out
fibish.go
fibish.out
fuzz_trailing_zero_field.go
idata.go
idata.out
leaf2.go
leaf.go
many_int_input.go
many_int_input.out
many_intstar_input.go
many_intstar_input.out
map.go
method_wrapper.go
more_intstar_input.go
more_intstar_input.out
named_results.go
named_results.out
named_return_stuff.go
named_return_stuff.out
open_defer_1.go
part_live_2.go
part_live.go
result_live.go
result_regalloc.go
return_stuff.go
return_stuff.out
s_sif_sif.go
spills3.go
spills4.go
store_reg_args.go
struct_3_string_input.go
struct_3_string_input.out
struct_lower_1.go
struct_lower_1.out
too_big_to_ssa.go
too_big_to_ssa.out
uglyfib.go
uglyfib.out
wrapdefer_largetmp.go
wrapdefer_largetmp.out
zombie_struct_select.go