fallback: legalize: G_CTLZ s32,s128

Run:explore-04ca53e65f-20261014-114124
Kind:fallback
Category:legalize: G_CTLZ s32,s128 NEW
Occurrences:1 in 1 configs, 1 test files
Snippet from:abds.a5e1b24e5f.ll (mutant of abds.ll) @abd_select_i128 via llvm-extract
Config:-mtriple=riscv32 -mattr=+zbb
Local check:reproduces at 04ca53e65f
Compiler Explorer:not uploaded (over --godbolt-limit or disabled)

Snippet:

@G = external global i128

; Function Attrs: nounwind
define i128 @abd_select_i128(i128 %a, i128 %b) #0 {
  %cmp = icmp slt i128 %a, %b
  %ab = select i1 %cmp, i128 %a, i128 %b
  %ba = select i1 %cmp, i128 %b, i128 %a
  %B = sdiv i128 %ab, %a
  %sub = sub i128 %ba, %ab
  store i128 %B, ptr @G, align 4
  ret i128 %sub
}

attributes #0 = { nounwind }

Reproduce:

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

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %1164:_(s32) = G_CTLZ %14:_(s128) (in function: abd_select_i128)
warning: Instruction selection used fallback path for abd_select_i128

Occurrences (1):

InputFunctionConfig
abds.a5e1b24e5f.ll (mutant of abds.ll)abd_select_i128-mtriple=riscv32 -mattr=+zbb

Generated 2026-10-15 08:05 UTC.