dfb369399d
Make ValueTracking directly call the KnownBits shift helpers, which provides more precise results. Unfortunately, ValueTracking has a special case where sometimes we determine non-zero shift amounts using isKnownNonZero(). I have my doubts about the usefulness of that special-case (it is only tested in a single unit test), but I've reproduced the special-case via an extra parameter to the KnownBits methods. Differential Revision: https://reviews.llvm.org/D151816
69 lines
2.5 KiB
LLVM
69 lines
2.5 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
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; RUN: opt -S -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s
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; These testcases aren't *identical* but they have the same/similar meaning.
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; The obvious case.
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define i32 @div(i32 %val, i32 %num) nounwind {
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; CHECK-LABEL: 'div'
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; CHECK-NEXT: Classifying expressions for: @div
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; CHECK-NEXT: %tmp1 = udiv i32 %val, %num
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; CHECK-NEXT: --> (%val /u %num) U: full-set S: full-set
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; CHECK-NEXT: %tmp2 = mul i32 %tmp1, %num
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; CHECK-NEXT: --> ((%val /u %num) * %num)<nuw> U: full-set S: full-set
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; CHECK-NEXT: Determining loop execution counts for: @div
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;
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%tmp1 = udiv i32 %val, %num
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%tmp2 = mul i32 %tmp1, %num
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ret i32 %tmp2
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}
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define i32 @sdiv(i32 %val, i32 %num) nounwind {
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; CHECK-LABEL: 'sdiv'
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; CHECK-NEXT: Classifying expressions for: @sdiv
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; CHECK-NEXT: %tmp1 = sdiv i32 %val, %num
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; CHECK-NEXT: --> %tmp1 U: full-set S: full-set
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; CHECK-NEXT: %tmp2 = mul i32 %tmp1, %num
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; CHECK-NEXT: --> (%num * %tmp1) U: full-set S: full-set
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; CHECK-NEXT: Determining loop execution counts for: @sdiv
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;
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%tmp1 = sdiv i32 %val, %num
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%tmp2 = mul i32 %tmp1, %num
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ret i32 %tmp2
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}
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; Or, it could be a number of equivalent patterns with mask:
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; b) x & (-1 << nbits)
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; d) x >> (32 - y) << (32 - y)
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define i32 @mask_b(i32 %val, i32 %numlowbits) nounwind {
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; CHECK-LABEL: 'mask_b'
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; CHECK-NEXT: Classifying expressions for: @mask_b
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; CHECK-NEXT: %mask = shl i32 -1, %numlowbits
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; CHECK-NEXT: --> %mask U: [-2147483648,0) S: [-2147483648,0)
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; CHECK-NEXT: %masked = and i32 %mask, %val
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; CHECK-NEXT: --> %masked U: full-set S: full-set
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; CHECK-NEXT: Determining loop execution counts for: @mask_b
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;
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%mask = shl i32 -1, %numlowbits
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%masked = and i32 %mask, %val
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ret i32 %masked
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}
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define i32 @mask_d(i32 %val, i32 %lowbits) nounwind {
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; CHECK-LABEL: 'mask_d'
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; CHECK-NEXT: Classifying expressions for: @mask_d
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; CHECK-NEXT: %numlowbits = sub i32 32, %lowbits
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; CHECK-NEXT: --> (32 + (-1 * %lowbits)) U: full-set S: full-set
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; CHECK-NEXT: %lowbitscleared = lshr i32 %val, %numlowbits
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; CHECK-NEXT: --> %lowbitscleared U: full-set S: full-set
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; CHECK-NEXT: %masked = shl i32 %lowbitscleared, %numlowbits
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; CHECK-NEXT: --> %masked U: full-set S: full-set
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; CHECK-NEXT: Determining loop execution counts for: @mask_d
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;
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%numlowbits = sub i32 32, %lowbits
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%lowbitscleared = lshr i32 %val, %numlowbits
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%masked = shl i32 %lowbitscleared, %numlowbits
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ret i32 %masked
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}
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