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c5e08120a4
The primary advantage is that loop optimizations will be applied in a stable order. This helps debugging and unit test creation. It is also a better overall implementation without pathologically bad performance on deep functions. On large functions (llvm-stress --size=200000 | opt -loops) Before: 0.1263s After: 0.0225s On deep functions (after tweaking llvm-stress, thanks Nadav): Before: 0.2281s After: 0.0227s See r158790 for more comments. The loop tree is now consistently generated in forward order, but loop passes are applied in reverse order over the program. If we have a loop optimization that prefers forward order, that can easily be achieved by adding a different type of LoopPassManager. llvm-svn: 159183
39 lines
672 B
LLVM
39 lines
672 B
LLVM
; RUN: opt < %s -lcssa -S | FileCheck %s
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; CHECK: exit1:
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; CHECK: .lcssa =
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; CHECK: exit2:
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; CHECK: .lcssa1 =
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; CHECK: exit3:
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; CHECK-NOT: .lcssa
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; Test to ensure that when there are multiple exit blocks, PHI nodes are
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; only inserted by LCSSA when there is a use dominated by a given exit
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; block.
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declare void @printf(i32 %i)
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define i32 @unused_phis() nounwind {
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entry:
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br label %loop
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loop:
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%i = phi i32 [0, %entry], [1, %then2]
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br i1 undef, label %exit1, label %then1
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then1:
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br i1 undef, label %exit2, label %then2
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then2:
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br i1 undef, label %exit3, label %loop
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exit1:
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call void @printf(i32 %i)
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ret i32 %i
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exit2:
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ret i32 %i
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exit3:
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ret i32 0
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}
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