[llvm] [LoopVectorize] LLVM fails to vectorise loops with multi-bool varables (PR #89226)

[David Sherwood via llvm-commits]

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@@ -47,3 +43,47 @@ for.cond.cleanup.loopexit:                        ; preds = %for.body
 for.cond.cleanup:                                 ; preds = %for.cond.cleanup.loopexit, %entry
   ret void
 }
+
+define i32 @multi_user_cmp(ptr readonly %a, i32 noundef %n) {
+; CHECK: LV: Found an estimated cost of 0 for VF 16 For instruction:   %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+; CHECK-NEXT: LV: Found an estimated cost of 0 for VF 16 For instruction:   %all.0.off010 = phi i1 [ true, %entry ], [ %all.0.off0., %for.body ]
+; CHECK-NEXT: LV: Found an estimated cost of 0 for VF 16 For instruction:   %any.0.off09 = phi i1 [ false, %entry ], [ %.any.0.off0, %for.body ]
+; CHECK-NEXT: LV: Found an estimated cost of 0 for VF 16 For instruction:   %arrayidx = getelementptr inbounds float, ptr %a, i64 %indvars.iv
+; CHECK-NEXT: LV: Found an estimated cost of 4 for VF 16 For instruction:   %load1 = load float, ptr %arrayidx, align 4
+; CHECK-NEXT: LV: Found an estimated cost of 4 for VF 16 For instruction:   %cmp1 = fcmp olt float %load1, 0.000000e+00
+; CHECK-NEXT: LV: Found an estimated cost of 1 for VF 16 For instruction:   %.any.0.off0 = select i1 %cmp1, i1 true, i1 %any.0.off09
+; CHECK-NEXT: LV: Found an estimated cost of 1 for VF 16 For instruction:   %all.0.off0. = select i1 %cmp1, i1 %all.0.off010, i1 false
+; CHECK-NEXT: LV: Found an estimated cost of 1 for VF 16 For instruction:   %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+; CHECK-NEXT: LV: Found an estimated cost of 1 for VF 16 For instruction:   %exitcond.not = icmp eq i64 %indvars.iv.next, %wide.trip.count
+; CHECK-NEXT: LV: Found an estimated cost of 0 for VF 16 For instruction:   br i1 %exitcond.not, label %exit, label %for.body
+; CHECK-NEXT: LV: Vector loop of width 16 costs: 0.
+entry:
+  %wide.trip.count = zext nneg i32 %n to i64
+  br label %for.body
+
+for.body:
+  %indvars.iv = phi i64 [ 0, %entry ], [ %indvars.iv.next, %for.body ]
+  %all.0.off010 = phi i1 [ true, %entry ], [ %all.0.off0., %for.body ]
+  %any.0.off09 = phi i1 [ false, %entry ], [ %.any.0.off0, %for.body ]
+  %arrayidx = getelementptr inbounds float, ptr %a, i64 %indvars.iv
+  %load1 = load float, ptr %arrayidx, align 4
+  %cmp1 = fcmp olt float %load1, 0.000000e+00
+  %.any.0.off0 = select i1 %cmp1, i1 true, i1 %any.0.off09
+  %all.0.off0. = select i1 %cmp1, i1 %all.0.off010, i1 false
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  %exitcond.not = icmp eq i64 %indvars.iv.next, %wide.trip.count
+  br i1 %exitcond.not, label %exit, label %for.body
+
+exit:
+  %0 = select i1 %.any.0.off0, i32 2, i32 3
+  %1 = select i1 %all.0.off0., i32 1, i32 %0
+  ret i32 %1
+}
+
+; CHECK-LABEL: define void @selects_1(
----------------
david-arm wrote:

I think this comment still stands. You can simplify the test by removing these check lines and simply adding a CHECK line for the selected VF to the existing CHECK lines above. If you do this then you can also simplify the test RUN line to be:

`; RUN: opt < %s -passes=loop-vectorize -debug-only=loop-vectorize -disable-output -S 2>&1 | FileCheck %s`

https://github.com/llvm/llvm-project/pull/89226