fallback: legalize: G_MERGE_VALUES s128,s64

Run:explore-bc8218b282-20261015-075519
Kind:fallback
Category:legalize: G_MERGE_VALUES s128,s64 NEW
Occurrences:1 in 1 configs, 1 test files
Snippet from:idiv_large.3d76e23519.ll (mutant of idiv_large.ll) @udiv_i65 via llvm-extract
Config:-mtriple=riscv64
Local check:reproduces at bc8218b282
Compiler Explorer:not uploaded (over --godbolt-limit or disabled)

Snippet:

@G.1 = external global i65

; Function Attrs: nounwind
define i65 @udiv_i65(i65 %x, i65 %y) #0 {
  %A = alloca i1, align 1
  store i1 false, ptr %A, align 1
  %L = load i1, ptr %A, align 1
  br i1 %L, label %T, label %F

BB:                                               ; preds = %F, %T
  %res = udiv i65 %x, %y
  %B = and i65 %y, %res
  store i65 %B, ptr @G.1, align 4
  ret i65 %res

T:                                                ; preds = %0
  br label %BB

F:                                                ; preds = %0
  br label %BB
}

attributes #0 = { nounwind }

Reproduce:

llc -mtriple=riscv64 -global-isel -global-isel-abort=2 -pass-remarks-missed=gisel.* snippet.ll -o -
llc -mtriple=riscv64 -global-isel=0 snippet.ll -o -

Local llc output:

remark: <unknown>:0:0: unable to legalize instruction: %32:_(s128) = G_MERGE_VALUES %37:_(s64), %38:_(s64) (in function: udiv_i65)
warning: Instruction selection used fallback path for udiv_i65

Occurrences (1):

InputFunctionConfig
idiv_large.3d76e23519.ll (mutant of idiv_large.ll)udiv_i65-mtriple=riscv64

Generated 2026-10-15 08:05 UTC.