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Enable the new LoopInfo algorithm by default.

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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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159183 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Andrew Trick
2012-06-26 04:11:38 +00:00
parent 5ac3f96c0e
commit c9b1e25493
10 changed files with 52 additions and 244 deletions
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4
test/Transforms/LCSSA/unused-phis.ll
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@@ -2,9 +2,9 @@
; CHECK: exit1:
; CHECK: .lcssa =
; CHECK: exit2:
; CHECK: .lcssa2 =
; CHECK: .lcssa1 =
; CHECK: exit3:
; CHECK-NOT: .lcssa1 =
; CHECK-NOT: .lcssa
; Test to ensure that when there are multiple exit blocks, PHI nodes are
; only inserted by LCSSA when there is a use dominated by a given exit