ffc922ec35
In some loops, we end up generating loop induction variables that look like:
{(-1 * (zext i16 (%i0 * %i1) to i32))<nsw>,+,1}
As opposed to the simpler:
{(zext i16 (%i0 * %i1) to i32),+,-1}
i.e we count up from -limit to 0, not the simpler counting down from limit to
0. This is because the scores, as LSR calculates them, are the same and the
second is filtered in place of the first. We end up with a redundant SUB from 0
in the code.
This patch tries to make the calculation of the setup cost a little more
thoroughly, recursing into the scev members to better approximate the setup
required. The cost function for comparing LSR costs is:
return std::tie(C1.NumRegs, C1.AddRecCost, C1.NumIVMuls, C1.NumBaseAdds,
C1.ScaleCost, C1.ImmCost, C1.SetupCost) <
std::tie(C2.NumRegs, C2.AddRecCost, C2.NumIVMuls, C2.NumBaseAdds,
C2.ScaleCost, C2.ImmCost, C2.SetupCost);
So this will only alter results if none of the other variables turn out to be
different.
Differential Revision: https://reviews.llvm.org/D58770
llvm-svn: 355597
56 lines
2.9 KiB
LLVM
56 lines
2.9 KiB
LLVM
; RUN: opt < %s -loop-reduce -lsr-recursive-setupcost=0 -S | FileCheck %s
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; This test is adapted from the n-body test of the LLVM test-suite: A bug in
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; r345114 caused LSR to generate incorrect code. The test verifies that the
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; induction variable generated for the inner loop depends on the induction
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; variable of the outer loop.
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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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%struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44 = type { double, double, double, double, double, double, double }
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; Function Attrs: nounwind uwtable
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define dso_local void @advance(i32 %nbodies, %struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44* nocapture %bodies) local_unnamed_addr #0 {
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; CHECK-LABEL: @advance(
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; CHECK: for.cond.loopexit:
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; CHECK: [[LSR_IV_NEXT:%.*]] = add i64 [[LSR_IV:%.*]], -1
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; CHECK: br label %for.body
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; CHECK: for.body:
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; CHECK: [[LSR_IV]] = phi i64 [ [[LSR_IV_NEXT]]
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; CHECK: br label %for.body3
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; CHECK: for.body3:
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; CHECK: [[LSR_IV1:%.*]] = phi i64 [ [[LSR_IV_NEXT2:%.*]], %for.body3 ], [ [[LSR_IV]], %for.body ]
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; CHECK: [[LSR_IV_NEXT2]] = add i64 [[LSR_IV1]], -1
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; CHECK: [[EXITCOND:%.*]] = icmp eq i64 [[LSR_IV_NEXT2]], 0
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; CHECK: br i1 [[EXITCOND]], label %for.cond.loopexit, label %for.body3
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;
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entry:
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%wide.trip.count = zext i32 %nbodies to i64
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br label %for.body
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for.cond.loopexit: ; preds = %for.body3
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%indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
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br label %for.body
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for.body: ; preds = %for.cond.loopexit, %entry
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%indvars.iv = phi i64 [ 1, %entry ], [ %indvars.iv.next, %for.cond.loopexit ]
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br label %for.body3
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for.body3: ; preds = %for.body3, %for.body
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%indvars.iv98 = phi i64 [ %indvars.iv, %for.body ], [ %indvars.iv.next99, %for.body3 ]
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%z9 = getelementptr inbounds %struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44, %struct.planet.0.3.6.11.12.15.16.17.24.25.26.33.44* %bodies, i64 %indvars.iv98, i32 2
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%tmp = load double, double* %z9, align 8, !tbaa !0
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%indvars.iv.next99 = add nuw nsw i64 %indvars.iv98, 1
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%exitcond = icmp eq i64 %indvars.iv.next99, %wide.trip.count
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br i1 %exitcond, label %for.cond.loopexit, label %for.body3
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}
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attributes #0 = { nounwind uwtable "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="x86-64" "target-features"="+fxsr,+mmx,+sse,+sse2,+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
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!0 = !{!1, !2, i64 16}
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!1 = !{!"planet", !2, i64 0, !2, i64 8, !2, i64 16, !2, i64 24, !2, i64 32, !2, i64 40, !2, i64 48}
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!2 = !{!"double", !3, i64 0}
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!3 = !{!"omnipotent char", !4, i64 0}
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!4 = !{!"Simple C/C++ TBAA"}
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