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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
62 lines
2.2 KiB
LLVM
62 lines
2.2 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 < %s | FileCheck %s
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; RUN: opt -S -disable-output "-passes=print<scalar-evolution>" < %s 2>&1 | FileCheck %s
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; The obvious case.
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define i32 @div(i32 %val) 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, 16
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; CHECK-NEXT: --> (%val /u 16) U: [0,268435456) S: [0,268435456)
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; CHECK-NEXT: %tmp2 = mul i32 %tmp1, 16
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; CHECK-NEXT: --> (16 * (%val /u 16))<nuw> U: [0,-15) S: [-2147483648,2147483633)
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; CHECK-NEXT: Determining loop execution counts for: @div
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;
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%tmp1 = udiv i32 %val, 16
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%tmp2 = mul i32 %tmp1, 16
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ret i32 %tmp2
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}
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define i32 @sdiv(i32 %val) 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, 16
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; CHECK-NEXT: --> %tmp1 U: [-134217728,134217728) S: [-134217728,134217728)
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; CHECK-NEXT: %tmp2 = mul i32 %tmp1, 16
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; CHECK-NEXT: --> (16 * %tmp1)<nsw> U: [0,-15) S: [-2147483648,2147483633)
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; CHECK-NEXT: Determining loop execution counts for: @sdiv
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;
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%tmp1 = sdiv i32 %val, 16
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%tmp2 = mul i32 %tmp1, 16
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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 >> nbits << nbits
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define i32 @mask_b(i32 %val) 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: %masked = and i32 %val, -16
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; CHECK-NEXT: --> (16 * (%val /u 16))<nuw> U: [0,-15) S: [-2147483648,2147483633)
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; CHECK-NEXT: Determining loop execution counts for: @mask_b
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;
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%masked = and i32 %val, -16
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ret i32 %masked
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}
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define i32 @mask_d(i32 %val) 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: %lowbitscleared = lshr i32 %val, 4
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; CHECK-NEXT: --> (%val /u 16) U: [0,268435456) S: [0,268435456)
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; CHECK-NEXT: %masked = shl i32 %lowbitscleared, 4
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; CHECK-NEXT: --> (16 * (%val /u 16))<nuw> U: [0,-15) S: [-2147483648,2147483633)
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; CHECK-NEXT: Determining loop execution counts for: @mask_d
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;
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%lowbitscleared = lshr i32 %val, 4
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%masked = shl i32 %lowbitscleared, 4
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ret i32 %masked
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}
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