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Summary: The existing implementation creates a symbolic SCEV expression every time we analyze a phi node and then has to remove it, when the analysis is finished. This is very expensive, and in most of the cases it's also unnecessary. According to the data I collected, ~60-70% of analyzed phi nodes (measured on SPEC) have the following form: PN = phi(Start, OP(Self, Constant)) Handling such cases separately significantly speeds this up. Reviewers: sanjoy, pete Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D32663 llvm-svn: 302096
19 lines
598 B
LLVM
19 lines
598 B
LLVM
; RUN: opt -analyze -scalar-evolution < %s -o - -S | FileCheck %s
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target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
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target triple = "x86_64-apple-macosx10.9.0"
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; Test that SCEV is capable of figuring out value of 'IV' that actually does not change.
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; CHECK: Classifying expressions for: @foo
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; CHECK: %iv.i = phi i64
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; CHECK: -5 U: [-5,-4) S: [-5,-4) Exits: -5 LoopDispositions: { %loop: Invariant }
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define void @foo() {
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entry:
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br label %loop
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loop:
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%iv.i = phi i64 [ -5, %entry ], [ %iv.next.i, %loop ]
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%iv.next.i = add nsw i64 %iv.i, 0
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br label %loop
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}
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