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289a0fd30f
When computing a range for a SCEVUnknown, today we use computeKnownBits for unsigned ranges, and computeNumSignBots for signed ranges. This means we miss opportunities to improve range results. One common missed pattern is that we have a signed range of a value which CKB can determine is positive, but CNSB doesn't convey that information. The current range includes the negative part, and is thus double the size. Per the removed comment, the original concern which delayed using both (after some code merging years back) was a compile time concern. CTMark results (provided by Nikita, thanks!) showed a geomean impact of about 0.1%. This doesn't seem large enough to avoid higher quality results. Differential Revision: https://reviews.llvm.org/D96534
44 lines
2.0 KiB
LLVM
44 lines
2.0 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
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; RUN: opt < %s -analyze -enable-new-pm=0 -scalar-evolution | FileCheck %s
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; RUN: opt < %s -disable-output "-passes=print<scalar-evolution>" 2>&1 | FileCheck %s
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target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-unknown-linux-gnu"
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; Previously in this case the max backedge count would be computed as 1/0, which
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; is correct but undesirable. It would also not fold as a constant, tripping
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; asserts in SCEV.
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define void @pluto(i32 %arg) {
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; CHECK-LABEL: 'pluto'
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; CHECK-NEXT: Classifying expressions for: @pluto
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; CHECK-NEXT: %tmp = ashr i32 %arg, 31
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; CHECK-NEXT: --> %tmp U: [-1,1) S: [-1,1)
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; CHECK-NEXT: %tmp1 = add nsw i32 %tmp, 2
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; CHECK-NEXT: --> (2 + %tmp)<nsw> U: [1,3) S: [1,3)
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; CHECK-NEXT: %tmp3 = phi i32 [ 0, %bb ], [ %tmp4, %bb2 ]
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; CHECK-NEXT: --> {0,+,(2 + %tmp)<nsw>}<nuw><nsw><%bb2> U: [0,3) S: [0,3) Exits: ((2 + %tmp)<nsw> * (1 /u (2 + %tmp)<nsw>)) LoopDispositions: { %bb2: Computable }
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; CHECK-NEXT: %tmp4 = add nuw nsw i32 %tmp1, %tmp3
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; CHECK-NEXT: --> {(2 + %tmp)<nsw>,+,(2 + %tmp)<nsw>}<nuw><nsw><%bb2> U: [1,5) S: [1,5) Exits: (2 + ((2 + %tmp)<nsw> * (1 /u (2 + %tmp)<nsw>)) + %tmp) LoopDispositions: { %bb2: Computable }
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; CHECK-NEXT: Determining loop execution counts for: @pluto
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; CHECK-NEXT: Loop %bb2: backedge-taken count is (1 /u (2 + %tmp)<nsw>)
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; CHECK-NEXT: Loop %bb2: max backedge-taken count is 1
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; CHECK-NEXT: Loop %bb2: Predicated backedge-taken count is (1 /u (2 + %tmp)<nsw>)
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; CHECK-NEXT: Predicates:
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; CHECK: Loop %bb2: Trip multiple is 1
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;
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bb:
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%tmp = ashr i32 %arg, 31
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%tmp1 = add nsw i32 %tmp, 2
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br label %bb2
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bb2: ; preds = %bb2, %bb
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%tmp3 = phi i32 [ 0, %bb ], [ %tmp4, %bb2 ]
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%tmp4 = add nuw nsw i32 %tmp1, %tmp3
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%tmp5 = icmp ult i32 %tmp4, 2
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br i1 %tmp5, label %bb2, label %bb6
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bb6: ; preds = %bb2
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ret void
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}
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