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6e6c58680c
Summary: The current loop complete unroll algorithm checks if unrolling complete will reduce the runtime by a certain percentage. If yes, it will apply a fixed boosting factor to the threshold (by discounting cost). The problem for this approach is that the threshold abruptly. This patch makes the boosting factor a function of runtime reduction percentage, capped by a fixed threshold. In this way, the threshold changes continuously. The patch also simplified the code by reducing one parameter in UP. The patch only affects code-gen of two speccpu2006 benchmark: 445.gobmk binary size decreases 0.08%, no performance change. 464.h264ref binary size increases 0.24%, no performance change. Reviewers: mzolotukhin, chandlerc Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D26989 llvm-svn: 290737
39 lines
1.6 KiB
LLVM
39 lines
1.6 KiB
LLVM
; RUN: opt < %s -S -loop-unroll -unroll-max-iteration-count-to-analyze=100 -unroll-threshold=12 -unroll-max-percent-threshold-boost=400 | FileCheck %s
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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@known_constant = internal unnamed_addr constant [10 x i32] [i32 0, i32 0, i32 0, i32 0, i32 1, i32 0, i32 0, i32 0, i32 0, i32 0], align 16
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; If a load becomes a constant after loop unrolling, we sometimes can simplify
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; CFG. This test verifies that we handle such cases.
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; After one operand in an instruction is constant-folded and the
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; instruction is simplified, the other operand might become dead.
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; In this test we have::
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; for i in 1..10:
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; r += A[i] * B[i]
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; A[i] is 0 almost at every iteration, so there is no need in loading B[i] at
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; all.
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; CHECK-LABEL: @unroll_dce
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; CHECK-NOT: br i1 %exitcond, label %for.end, label %for.body
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define i32 @unroll_dce(i32* noalias nocapture readonly %b) {
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entry:
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br label %for.body
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for.body: ; preds = %for.body, %entry
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%iv.0 = phi i64 [ 0, %entry ], [ %iv.1, %for.body ]
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%r.0 = phi i32 [ 0, %entry ], [ %r.1, %for.body ]
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%arrayidx1 = getelementptr inbounds [10 x i32], [10 x i32]* @known_constant, i64 0, i64 %iv.0
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%x1 = load i32, i32* %arrayidx1, align 4
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%arrayidx2 = getelementptr inbounds i32, i32* %b, i64 %iv.0
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%x2 = load i32, i32* %arrayidx2, align 4
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%mul = mul i32 %x1, %x2
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%r.1 = add i32 %mul, %r.0
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%iv.1 = add nuw nsw i64 %iv.0, 1
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%exitcond = icmp eq i64 %iv.1, 10
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br i1 %exitcond, label %for.end, label %for.body
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for.end: ; preds = %for.body
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ret i32 %r.1
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}
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