[Bug target/114100] [avr] Inefficient indirect addressing on Reduced Tiny
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114100 --- Comment #5 from GCC Commits --- The master branch has been updated by Georg-Johann Lay : https://gcc.gnu.org/g:c0f5b6caff669037444506cb6008a378356ec209 commit r14-9281-gc0f5b6caff669037444506cb6008a378356ec209 Author: Georg-Johann Lay Date: Sun Mar 3 18:15:58 2024 +0100 AVR: ad target/114100 - Don't print unused frame pointer adjustments. Without -mfuse-add, when fake reg+offset addressing is used, the output routines are saving some instructions when the base reg is unused after. This patch adds that optimization for the case when the base is the frame pointer and the frame pointer adjustments are split away from the move insn by -mfuse-add in .split2. Direct usage of reg_unused_after is not possible because that function looks at the destination of the current insn, which won't work for offsetting the frame pointer in printing PLUS code. It can use an extended version of _reg_unused_after though. gcc/ PR target/114100 * config/avr/avr-protos.h (_reg_unused_after): Remove proto. * config/avr/avr.cc (_reg_unused_after): Make static. And add 3rd argument to skip the current insn. (reg_unused_after): Adjust call of reg_unused_after. (avr_out_plus_1) [AVR_TINY && -mfuse-add >= 2]: Don't output unneeded frame pointer adjustments.
[Bug target/114100] [avr] Inefficient indirect addressing on Reduced Tiny
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114100 --- Comment #4 from GCC Commits --- The master branch has been updated by Georg-Johann Lay : https://gcc.gnu.org/g:96bad6c06d0108014a2b0e5d0921cb18066bb789 commit r14-9271-g96bad6c06d0108014a2b0e5d0921cb18066bb789 Author: Georg-Johann Lay Date: Sat Mar 2 10:03:06 2024 +0100 AVR: target/114100 - Factor in -mtiny-stack in frame pointer adjustments gcc/ PR target/114100 * config/avr/avr.cc (avr_out_plus_1) [-mtiny-stack]: Only adjust the low part of the frame pointer with 8-bit stack pointer.
[Bug target/114100] [avr] Inefficient indirect addressing on Reduced Tiny
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114100 Georg-Johann Lay changed: What|Removed |Added Status|NEW |RESOLVED Resolution|--- |FIXED --- Comment #3 from Georg-Johann Lay --- Improved in v14
[Bug target/114100] [avr] Inefficient indirect addressing on Reduced Tiny
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114100
--- Comment #2 from GCC Commits ---
The master branch has been updated by Georg-Johann Lay :
https://gcc.gnu.org/g:cda3836161834c5f21f264885891fe4d0ce90da1
commit r14-9244-gcda3836161834c5f21f264885891fe4d0ce90da1
Author: Georg-Johann Lay
Date: Thu Feb 29 17:19:27 2024 +0100
AVR: target/114100 - Better indirect accesses for reduced Tiny
The Reduced Tiny core does not support indirect addressing with offset,
which basically means that every indirect memory access with a size
of more than one byte is effectively POST_INC or PRE_DEC. The lack of
that addressing mode is currently handled by pretending to support it,
and then let the insn printers add and subtract again offsets as needed.
For example, the following C code
int vars[10];
void inc_var2 (void) {
++vars[2];
}
is compiled to:
ldi r30,lo8(vars) ; 14 [c=4 l=2] *movhi/4
ldi r31,hi8(vars)
subi r30,lo8(-(4)); 15 [c=8 l=6] *movhi/2
sbci r31,hi8(-(4))
ld r20,Z+
ld r21,Z
subi r30,lo8((4+1))
sbci r31,hi8((4+1))
subi r20,-1 ; 16 [c=4 l=2] *addhi3_clobber/1
sbci r21,-1
subi r30,lo8(-(4+1)); 17 [c=4 l=4] *movhi/3
sbci r31,hi8(-(4+1))
st Z,r21
st -Z,r20
where the code could be -- and with this patch actually is -- like
ldi r30,lo8(vars+4); 28 [c=4 l=2] *movhi/4
ldi r31,hi8(vars+4)
ld r20,Z+ ; 17 [c=8 l=2] *movhi/2
ld r21,Z+
subi r20,-1; 19 [c=4 l=2] *addhi3_clobber/1
sbci r21,-1
st -Z,r21 ; 30 [c=4 l=2] *movhi/3
st -Z,r20
This is achieved in two steps:
- A post-reload split into "real" instructions during .split2.
- A new avr-specific mini pass .avr-fuse-add that runs before
RTL peephole and that tries to combine the generated pointer
additions into memory accesses to form POST_INC or PRE_DEC.
gcc/
PR target/114100
* doc/invoke.texi (AVR Options) <-mfuse-add>: Document.
* config/avr/avr.opt (-mfuse-add=): New target option.
* common/config/avr/avr-common.cc (avr_option_optimization_table)
[OPT_LEVELS_1_PLUS]: Set -mfuse-add=1.
[OPT_LEVELS_2_PLUS]: Set -mfuse-add=2.
* config/avr/avr-passes.def (avr_pass_fuse_add): Insert new pass.
* config/avr/avr-protos.h (avr_split_tiny_move)
(make_avr_pass_fuse_add): New protos.
* config/avr/avr.md [AVR_TINY]: New post-reload splitter uses
avr_split_tiny_move to split indirect memory accesses.
(gen_move_clobbercc): New define_expand helper.
* config/avr/avr.cc (avr_pass_data_fuse_add): New pass data.
(avr_pass_fuse_add): New class from rtl_opt_pass.
(make_avr_pass_fuse_add, avr_split_tiny_move): New functions.
(reg_seen_between_p, emit_move_ccc, emit_move_ccc_after): New
functions.
(avr_legitimate_address_p) [AVR_TINY]: Don't restrict offsets
of PLUS addressing for AVR_TINY.
(avr_regno_mode_code_ok_for_base_p) [AVR_TINY]: Ignore -mstrict-X.
(avr_out_plus_1) [AVR_TINY]: Tweak ++Y and --Y.
(avr_mode_code_base_reg_class) [AVR_TINY]: Always return
POINTER_REGS.
[Bug target/114100] [avr] Inefficient indirect addressing on Reduced Tiny
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114100 Andrew Pinski changed: What|Removed |Added Severity|normal |enhancement Ever confirmed|0 |1 Status|UNCONFIRMED |NEW Last reconfirmed||2024-02-25 --- Comment #1 from Andrew Pinski --- Confirmed. One way of improving this is to slightly increase the cost of the indirect addressing with offset for these cores.
[Bug target/114100] [avr] Inefficient indirect addressing on Reduced Tiny
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114100 Georg-Johann Lay changed: What|Removed |Added Target Milestone|--- |14.0 Priority|P3 |P4 Keywords||missed-optimization Target||avr
