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Revert part of "Cleanup some GraphTraits iteration code"

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This reverts part of r300656, which caused a regression in
propagateMassToSuccessors by counting edges n^2 times, where n is the
number of edges from the source basic block to the same successor basic
block. The result was both incorrect and very slow to compute for large
values of n (e.g. switches with multiple cases that go to the same basic
block).

Patch by Andrew Scheidecker!

llvm-svn: 320208
This commit is contained in:
Duncan P. N. Exon Smith 2017-12-08 22:42:43 +00:00
parent 1a38944443
commit 27a3b015ef
2 changed files with 28 additions and 3 deletions
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9
include/llvm/Analysis/BlockFrequencyInfoImpl.h
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@ -1314,9 +1314,12 @@ BlockFrequencyInfoImpl<BT>::propagateMassToSuccessors(LoopData *OuterLoop,
return false;
} else {
const BlockT *BB = getBlock(Node);
for (const auto Succ : children<const BlockT *>(BB))
if (!addToDist(Dist, OuterLoop, Node, getNode(Succ),
getWeightFromBranchProb(BPI->getEdgeProbability(BB, Succ))))
for (auto SI = GraphTraits<const BlockT *>::child_begin(BB),
SE = GraphTraits<const BlockT *>::child_end(BB);
SI != SE; ++SI)
if (!addToDist(
Dist, OuterLoop, Node, getNode(*SI),
getWeightFromBranchProb(BPI->getEdgeProbability(BB, SI))))
// Irreducible backedge.
return false;
}

22
test/Analysis/BlockFrequencyInfo/redundant_edges.ll Normal file
View File

@ -0,0 +1,22 @@
; RUN: opt < %s -analyze -block-freq | FileCheck %s
; RUN: opt < %s -analyze -lazy-block-freq | FileCheck %s
; RUN: opt < %s -passes='print<block-freq>' -disable-output 2>&1 | FileCheck %s
define void @test1() {
; CHECK-LABEL: Printing analysis {{.*}} for function 'test1':
; CHECK-NEXT: block-frequency-info: test1
; CHECK-NEXT: entry: float = 1.0, int = [[ENTRY:[0-9]+]]
entry:
br label %loop
; CHECK-NEXT: loop: float = 32.0
loop:
switch i32 undef, label %loop [
i32 0, label %return
i32 1, label %return
]
; CHECK-NEXT: return: float = 1.0
return:
ret void
}