On 3/29/25 17:58, Jeff Law wrote:
> On 3/29/25 6:49 PM, Vineet Gupta wrote:
>> changes since v2
>> - dump log sanfu
>>
>> ---
>> vsetvl phase4 uses LCM guided info to insert VSETVL insns.
>> It has an additional loop to insert missing vsetvls on certain edges.
>> Currently it asserts/aborts on encountering EDGE_ABNORMAL.
>> When enabling go frontend with V enabled, libgo build hits the assert.
>>
>> It seems to be safe to just skip the abnormal edge.
>>
>> Verified that a go toolchain build with the fix completes successfully
>> and runs the testsuite.
>>
>> rv64imafdcv_zicbom_zicboz_zicntr_zicond_zicsr_zifencei_zihintntl_zihintpause_zihpm_zfa_zfhmin_zba_zbb_zbs_zkt_zvbb_zvkt/
>> lp64d/ medlow | 738 / 146 | 7 / 3 | 72 / 12 |
>>
>> Also to make sure nothing regressed on rvv and go side, did additional 2
>> sets of runs.
>>
>> 1. RVV build, go disabled, w/ and w/o fix
>> rv64imafdcv_zvl256b_zba_zbb_zbs_zicond/ lp64d/ medlow | 244 / 96 |
>> 7 / 3 | 67 / 12 |
>> rv64imafdcv_zvl256b_zba_zbb_zbs_zicond/ lp64d/ medlow | 244 / 96 |
>> 7 / 3 | 67 / 12 |
>>
>> 2. go enabled, RVV disabled, w/ and w/o fix
>> rv64imafdc_zba_zbb_zbs_zicond_zfa/ lp64d/ medlow | 155 / 47 | 0 /
>> 0 | 0 / 0 |
>> rv64imafdc_zba_zbb_zbs_zicond_zfa/ lp64d/ medlow | 155 / 47 | 0 /
>> 0 | 0 / 0 |
>>
>> PR target/119533
>>
>> gcc/ChangeLog:
>>
>> * config/riscv/riscv-vsetvl.cc (pre_vsetvl::emit_vsetvl): skip
>> EDGE_ABNORMAL.
>>
>> gcc/testsuite/ChangeLog:
>>
>> * go.dg/pr119533-riscv.go: New test.
> So presumably it wants to insert on the EH edge for a reason. Just
> skipping the edge is probably wrong.
>
> The way these scenarios are handled in the more generic LCM passes is to
> kill all values on the EH edge. With all values killed on the EH edge,
> no redundancy exists which should require insertion on the edge.
Lets do some dump diving - pun intended.
Failure happens at the following abnormal edge:
Insert missed vsetvl info at edge(bb 42 -> bb 64):VALID (insn 663, bb 64)
Where bb 64 corresponds to unwinder call so clearly EH related.
(code_label/s 474 591 476 64 37 (nil) [1 uses])
(note 476 474 438 64 [bb 64] NOTE_INSN_BASIC_BLOCK)
(call_insn 438 476 439 64 (parallel [
(call (mem:SI (symbol_ref:DI ("_Unwind_Resume") [flags 0x41]
<function_decl 0x7ef116e59400 __builtin_unwind_resume>) [0
__builtin_unwind_resume S4 A32])
(const_int 0 [0]))
(use (unspec:SI [
(const_int 0 [0])
] UNSPEC_CALLEE_CC))
(clobber (reg:SI 1 ra))
]) 456 {call_internal}
(expr_list:REG_DEAD (reg:DI 10 a0)
(expr_list:REG_CALL_DECL (symbol_ref:DI ("_Unwind_Resume") [flags
0x41] <function_decl 0x7ef116e59400 __builtin_unwind_resume>)
(expr_list:REG_NORETURN (const_int 0 [0])
(nil))))
(expr_list:DI (use (reg:DI 10 a0))
(nil)))
(barrier 439 438 617)
The edge 42 -> 64 already exists at the entry of vsetvl, so its not something
that the vsetvl/LCM creates.
Entering Lazy VSETVL PASS
...
...
;; 27 succs { 64 28 }
;; 28 succs { 64 29 } <---
;; 29 succs { 30 43 }
;; 30 succs { 64 31 }
;; 31 succs { 32 43 }
;; 32 succs { 64 33 }
;; 33 succs { 64 34 }
;; 34 succs { 64 35 }
;; 35 succs { 36 39 }
;; 36 succs { 64 37 }
;; 37 succs { 64 38 }
;; 38 succs { 39 }
;; 39 succs { 64 40 }
;; 40 succs { 64 41 }
;; 41 succs { 64 42 }
;; 42 succs { 64 43 } <----
...
...
In the working case, --param=vsetvl-strategy=simple, in cprop (just before
vsetvl), I don't see any jumps to the code label of bb 64 (with Unwinder call)
either.
I don't think vsetvl LCM is supposed to prune this edge out. In fact in the
routine to prepare LCM bitmaps I skip bb 42 (by checking for EDGE_CRITICAL in
invalid_opt_bb_p ()
The problem now happens in bb 28, which also happens to have edge to 64.
So it seems to me that it should be safe to just skip the abnormal edge.
Thx,
-Vineet
