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[SCEV] Add test where result depends on order loop guards are applied. 

This patch adds 2 test cases where we fail to determine a tight bound on
the backedge taken count because the ULT condition is applied before the
signed conditions. The order the conditions are applied impacts which
min/max folds are applied.
This commit is contained in:
Florian Hahn 2021-12-15 19:07:25 +00:00
parent 001914975d
commit eea568927b
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1 changed files with 73 additions and 0 deletions
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73
llvm/test/Analysis/ScalarEvolution/max-backedge-taken-count-guard-info.ll
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@ -1475,3 +1475,76 @@ loop:
exit:
ret void
}
define i32 @sle_sgt_ult_umax_to_smax(i32 %num) {
; CHECK-LABEL: 'sle_sgt_ult_umax_to_smax'
; CHECK-NEXT: Classifying expressions for: @sle_sgt_ult_umax_to_smax
; CHECK-NEXT: %iv = phi i32 [ 0, %guard.3 ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,4}<nuw><%loop> U: [0,-3) S: [-2147483648,2147483645) Exits: (4 * ((-4 + %num) /u 4))<nuw> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = add nuw i32 %iv, 4
; CHECK-NEXT: --> {4,+,4}<nuw><%loop> U: [4,-3) S: [-2147483648,2147483645) Exits: (4 + (4 * ((-4 + %num) /u 4))<nuw>) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @sle_sgt_ult_umax_to_smax
; CHECK-NEXT: Loop %loop: backedge-taken count is ((-4 + %num) /u 4)
; CHECK-NEXT: Loop %loop: max backedge-taken count is 1073741823
; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is ((-4 + %num) /u 4)
; CHECK-NEXT: Predicates:
; CHECK: Loop %loop: Trip multiple is 1
;
guard.1:
%cmp.1 = icmp sle i32 %num, 0
br i1 %cmp.1, label %exit, label %guard.2
guard.2:
%cmp.2 = icmp sgt i32 %num, 28
br i1 %cmp.2, label %exit, label %guard.3
guard.3:
%cmp.3 = icmp ult i32 %num, 4
br i1 %cmp.3, label %exit, label %loop
loop:
%iv = phi i32 [ 0, %guard.3 ], [ %iv.next, %loop ]
%iv.next = add nuw i32 %iv, 4
%ec = icmp eq i32 %iv.next, %num
br i1 %ec, label %exit, label %loop
exit:
ret i32 0
}
; Similar to @sle_sgt_ult_umax_to_smax but with different predicate order.
define i32 @ult_sle_sgt_umax_to_smax(i32 %num) {
; CHECK-LABEL: 'ult_sle_sgt_umax_to_smax'
; CHECK-NEXT: Classifying expressions for: @ult_sle_sgt_umax_to_smax
; CHECK-NEXT: %iv = phi i32 [ 0, %guard.3 ], [ %iv.next, %loop ]
; CHECK-NEXT: --> {0,+,4}<nuw><%loop> U: [0,25) S: [0,25) Exits: (4 * ((-4 + %num) /u 4))<nuw> LoopDispositions: { %loop: Computable }
; CHECK-NEXT: %iv.next = add nuw i32 %iv, 4
; CHECK-NEXT: --> {4,+,4}<nuw><%loop> U: [4,29) S: [4,29) Exits: (4 + (4 * ((-4 + %num) /u 4))<nuw>) LoopDispositions: { %loop: Computable }
; CHECK-NEXT: Determining loop execution counts for: @ult_sle_sgt_umax_to_smax
; CHECK-NEXT: Loop %loop: backedge-taken count is ((-4 + %num) /u 4)
; CHECK-NEXT: Loop %loop: max backedge-taken count is 6
; CHECK-NEXT: Loop %loop: Predicated backedge-taken count is ((-4 + %num) /u 4)
; CHECK-NEXT: Predicates:
; CHECK: Loop %loop: Trip multiple is 1
;
guard.1:
%cmp.1 = icmp ult i32 %num, 4
br i1 %cmp.1, label %exit, label %guard.2
guard.2:
%cmp.2 = icmp sgt i32 %num, 28
br i1 %cmp.2, label %exit, label %guard.3
guard.3:
%cmp.3 = icmp sle i32 %num, 0
br i1 %cmp.3, label %exit, label %loop
loop:
%iv = phi i32 [ 0, %guard.3 ], [ %iv.next, %loop ]
%iv.next = add nuw i32 %iv, 4
%ec = icmp eq i32 %iv.next, %num
br i1 %ec, label %exit, label %loop
exit:
ret i32 0
}