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7e9ed1d023
Summary: Related to https://bugs.llvm.org/show_bug.cgi?id=37793, https://reviews.llvm.org/D46760#1127287 We'd like to do this canonicalization https://rise4fun.com/Alive/Gmc But it is currently restricted by rL155136 / rL155362, which says: ``` // This is a constant shift of a constant shift. Be careful about hiding // shl instructions behind bit masks. They are used to represent multiplies // by a constant, and it is important that simple arithmetic expressions // are still recognizable by scalar evolution. // // The transforms applied to shl are very similar to the transforms applied // to mul by constant. We can be more aggressive about optimizing right // shifts. // // Combinations of right and left shifts will still be optimized in // DAGCombine where scalar evolution no longer applies. ``` I think these tests show that for *constants*, SCEV has no issues with that canonicalization. Reviewers: mkazantsev, spatel, efriedma, sanjoy Reviewed By: mkazantsev Subscribers: sanjoy, javed.absar, llvm-commits, stoklund, bixia Differential Revision: https://reviews.llvm.org/D48229 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@335101 91177308-0d34-0410-b5e6-96231b3b80d8
69 lines
2.4 KiB
LLVM
69 lines
2.4 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_analyze_test_checks.py
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; RUN: opt -S -analyze -scalar-evolution < %s | 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) 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: full-set S: full-set
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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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