fallback: legalize: G_CTLZ_ZERO_POISON s32,s128

Run:explore-bc8218b282-20261015-075519
Kind:fallback
Category:legalize: G_CTLZ_ZERO_POISON s32,s128
Occurrences:11 in 6 configs, 6 test files
Snippet from:idiv_large.ll @udiv_i128 via llvm-extract
Config:-mtriple=riscv32
Local check:reproduces at bc8218b282
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 (11):

InputFunctionConfig
idiv_large.lludiv_i128-mtriple=riscv32
div_minsize.599fd9ce2b.ll (mutant of div_minsize.ll)i128_sdiv-mtriple=riscv32 -mattr=+m -verify-machineinstrs
idiv_large.180af2159c.ll (mutant of idiv_large.ll)udiv_i128-mtriple=riscv32
idiv_large.97919c1ba4.ll (mutant of idiv_large.ll)udiv_i128-mtriple=riscv32
idiv_large.aa32c6e232.ll (mutant of idiv_large.ll)udiv_i128-mtriple=riscv32
rv32zba.7256bee96a.ll (mutant of rv32zba.ll)addmul24-mtriple=riscv32 -mattr=+m,+xandesperf -verify-machineinstrs
rv32zba.8073e59aad.ll (mutant of rv32zba.ll)addmul24-mtriple=riscv32 -mattr=+m -verify-machineinstrs
rv32zba.ddcb34010c.ll (mutant of rv32zba.ll)addmul24-mtriple=riscv32 -mattr=+m,+zba -verify-machineinstrs
shifts.35f6704ad9.ll (mutant of shifts.ll)shl128-mtriple=riscv32 -verify-machineinstrs
umulo-128-legalisation-lowering.4e403f0b76.ll (mutant of umulo-128-legalisation-lowering.ll)muloti_test-mtriple=riscv32 -mattr=+m
wide-scalar-shift-legalization.ac8a9997e7.ll (mutant of wide-scalar-shift-legalization.ll)lshr_16bytes-mtriple=riscv32 -verify-machineinstrs

Generated 2026-10-15 08:05 UTC.