fallback: translate: call llvm.vp.reduce.add.nxv8i32

Snippet:

define signext i32 @sum(ptr %a, i32 signext %n, i1 %prof.min.iters.check, <vscale x 8 x i1> %0, <vscale x 8 x i1> %1) {
entry:
  br i1 %prof.min.iters.check, label %for.body, label %vector.ph

vector.ph:                                        ; preds = %entry
  %2 = tail call i32 @llvm.vp.reduce.add.nxv8i32(i32 0, <vscale x 8 x i32> zeroinitializer, <vscale x 8 x i1> %0, i32 1)
  br label %for.end

for.body:                                         ; preds = %for.body, %entry
  %indvars.iv = phi i64 [ %indvars.iv.next, %for.body ], [ 0, %entry ]
  %red.05 = phi i32 [ %3, %for.body ], [ 0, %entry ]
  %arrayidx = getelementptr i32, ptr %a, i64 %indvars.iv
  %3 = load i32, ptr %arrayidx, align 4
  %indvars.iv.next = add i64 %indvars.iv, 1
  %exitcond.not = icmp eq i32 %n, 0
  br i1 %exitcond.not, label %for.end, label %for.body

for.end:                                          ; preds = %for.body, %vector.ph
  %red.0.lcssa = phi i32 [ %2, %vector.ph ], [ %red.05, %for.body ]
  ret i32 %red.0.lcssa
}

; Function Attrs: nocallback nofree nosync nounwind speculatable willreturn memory(none)
declare i32 @llvm.vp.reduce.add.nxv8i32(i32, <vscale x 8 x i32>, <vscale x 8 x i1>, i32) #0

attributes #0 = { nocallback nofree nosync nounwind speculatable willreturn memory(none) }

Reproduce:

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

Local llc output:

remark: <unknown>:0:0: unable to translate instruction: call llvm.vp.reduce.add.nxv8i32: '  %2 = tail call i32 @llvm.vp.reduce.add.nxv8i32(i32 0, <vscale x 8 x i32> zeroinitializer, <vscale x 8 x i1> %0, i32 1)' (in function: sum)
warning: Instruction selection used fallback path for sum

Occurrences (4):

Generated 2026-10-15 08:05 UTC.