fallback: legalize: G_CTLZ_ZERO

fallback: legalize: G_CTLZ_ZERO_POISON s32,s128

Run:	main-04ca53e65f-20261014-105623
Kind:	fallback
Category:	legalize: G_CTLZ_ZERO_POISON s32,s128
Occurrences:	33 in 24 configs, 10 test files
Snippet from:	idiv_large.ll @udiv_i128 via llvm-extract
Config:	`-mtriple=riscv32`
Local check:	reproduces at 04ca53e65f
Compiler Explorer:	not uploaded (over --godbolt-limit or disabled)

Snippet:

; Function Attrs: nounwind
define i128 @udiv_i128(i128 %x, i128 %y) #0 {
  %res = udiv i128 %x, %y
  ret i128 %res
}

attributes #0 = { nounwind }

Reproduce:

llc -mtriple=riscv32 -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv32 -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %1031:_(s32) = G_CTLZ_ZERO_POISON %6:_(s128) (in function: udiv_i128)
warning: Instruction selection used fallback path for udiv_i128

Occurrences (33):

Input	Function	Config
idiv_large.ll	udiv_i128	`-mtriple=riscv32`
add-before-shl.0c7cd91e29.ll (mutant of add-before-shl.ll)	add_wide_operand	`-mtriple=riscv32 -verify-machineinstrs -M no-aliases`
add-before-shl.5b93550397.ll (mutant of add-before-shl.ll)	add_wide_operand	`-mtriple=riscv32 -mattr=+c -verify-machineinstrs -M no-aliases`
add-before-shl.7f6b14745f.ll (mutant of add-before-shl.ll)	add_wide_operand	`-mtriple=riscv32 -mattr=+zca -verify-machineinstrs -M no-aliases`
bfloat-imm.b7a5877d3e.ll (mutant of bfloat-imm.ll)	poison	`-mtriple=riscv32 -mattr=+zfbfmin -verify-machineinstrs -target-abi ilp32f`
callee-saved-gprs.1421d23167.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+zcmp -verify-machineinstrs -frame-pointer=all`
callee-saved-gprs.2ad2bc7a3d.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+zilsd -target-abi ilp32e -verify-machineinstrs`
callee-saved-gprs.4105059aac.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+zilsd -verify-machineinstrs`
callee-saved-gprs.426eacf66c.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+f -target-abi ilp32f -verify-machineinstrs`
callee-saved-gprs.4bee1e9301.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -verify-machineinstrs`
callee-saved-gprs.6d1f0d5d5c.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+zilsd -verify-machineinstrs -frame-pointer=all`
callee-saved-gprs.6d8b2164ae.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -verify-machineinstrs -frame-pointer=all`
callee-saved-gprs.78ce5ddb8b.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+d -target-abi ilp32f -verify-machineinstrs`
callee-saved-gprs.7dc9b6409a.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+zcmp -verify-machineinstrs`
callee-saved-gprs.aede55e146.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+zilsd,+zilsd-word-align -target-abi ilp32e -verify-machineinstrs`
callee-saved-gprs.e9e6b4380f.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+d -target-abi ilp32d -verify-machineinstrs`
callee-saved-gprs.f06ce6900f.ll (mutant of callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -target-abi ilp32e -verify-machineinstrs`
calling-conv-ilp32-ilp32f-common.969c14742c.ll (mutant of calling-conv-ilp32-ilp32f-common.ll)	callee_small_scalar_ret	`-mtriple=riscv32 -verify-machineinstrs -frame-pointer=all`
calling-conv-ilp32-ilp32f-common.dc932d76d4.ll (mutant of calling-conv-ilp32-ilp32f-common.ll)	callee_small_scalar_ret	`-mtriple=riscv32 -verify-machineinstrs`
calling-conv-ilp32-ilp32f-common.dce718b465.ll (mutant of calling-conv-ilp32-ilp32f-common.ll)	callee_small_scalar_ret	`-mtriple=riscv32 -verify-machineinstrs -frame-pointer=all -mattr=+f -target-abi ilp32f`
calling-conv-ilp32-ilp32f-common.f0ce2fcc20.ll (mutant of calling-conv-ilp32-ilp32f-common.ll)	callee_small_scalar_ret	`-mtriple=riscv32 -mattr=+f -target-abi ilp32f -verify-machineinstrs`
calling-conv-ilp32.8ca17eb543.ll (mutant of calling-conv-ilp32.ll)	callee_tiny_scalar_ret	`-mtriple=riscv32 -verify-machineinstrs -frame-pointer=all`
calling-conv-ilp32.cb787d3bb5.ll (mutant of calling-conv-ilp32.ll)	callee_tiny_scalar_ret	`-mtriple=riscv32 -verify-machineinstrs`
div_minsize.d96f398122.ll (mutant of div_minsize.ll)	i128_sdiv	`-mtriple=riscv32 -mattr=+m -verify-machineinstrs`
elf-preemption.46e2effee0.ll (mutant of elf-preemption.ll)	get_protected_var	`-mtriple=riscv32 -relocation-model=pic`
elf-preemption.bbd104a272.ll (mutant of elf-preemption.ll)	get_protected_var	`-mtriple=riscv32 -relocation-model=static`
idiv_large.3b3f40a374.ll (mutant of idiv_large.ll)	udiv_i128	`-mtriple=riscv32`
idiv_large.5fc4464b83.ll (mutant of idiv_large.ll)	udiv_i128	`-mtriple=riscv32`
idiv_large.864a6a8953.ll (mutant of idiv_large.ll)	udiv_i128	`-mtriple=riscv32`
idiv_large.a31f048984.ll (mutant of idiv_large.ll)	udiv_i128	`-mtriple=riscv32`
select-optimize-multiple.d0ff0418bd.ll (mutant of select-optimize-multiple.ll)	cmov128	`-mtriple=riscv32 -mattr=+d -target-abi=ilp32 -verify-machineinstrs`
xqccmp-callee-saved-gprs.58d7e3c30a.ll (mutant of xqccmp-callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+xqccmp -verify-machineinstrs`
xqccmp-callee-saved-gprs.f93fb55937.ll (mutant of xqccmp-callee-saved-gprs.ll)	varargs	`-mtriple=riscv32 -mattr=+xqccmp -verify-machineinstrs -frame-pointer=all`

Generated 2026-10-15 08:05 UTC.