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Update edge weights correctly in replaceSuccessor().

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When replacing Old with New, it can happen that New is already a
successor. Add the old and new edge weights instead of creating a
duplicate edge.

llvm-svn: 161653
This commit is contained in:
Jakob Stoklund Olesen 2012-08-10 03:23:27 +00:00
parent 8a1cdcb7fc
commit 52532aa712
2 changed files with 34 additions and 10 deletions
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42
lib/CodeGen/MachineBasicBlock.cpp
View File

@ -478,18 +478,42 @@ MachineBasicBlock::removeSuccessor(succ_iterator I) {
void MachineBasicBlock::replaceSuccessor(MachineBasicBlock *Old,
MachineBasicBlock *New) {
uint32_t weight = 0;
succ_iterator SI = std::find(Successors.begin(), Successors.end(), Old);
if (Old == New)
return;
// If Weight list is empty it means we don't use it (disabled optimization).
if (!Weights.empty()) {
weight_iterator WI = getWeightIterator(SI);
weight = *WI;
succ_iterator E = succ_end();
succ_iterator NewI = E;
succ_iterator OldI = E;
for (succ_iterator I = succ_begin(); I != E; ++I) {
if (*I == Old) {
OldI = I;
if (NewI != E)
break;
}
if (*I == New) {
NewI = I;
if (OldI != E)
break;
}
}
assert(OldI != E && "Old is not a successor of this block");
Old->removePredecessor(this);
// If New isn't already a successor, let it take Old's place.
if (NewI == E) {
New->addPredecessor(this);
*OldI = New;
return;
}
// Update the successor information.
removeSuccessor(SI);
addSuccessor(New, weight);
// New is already a successor.
// Update its weight instead of adding a duplicate edge.
if (!Weights.empty()) {
weight_iterator OldWI = getWeightIterator(OldI);
*getWeightIterator(NewI) += *OldWI;
Weights.erase(OldWI);
}
Successors.erase(OldI);
}
void MachineBasicBlock::addPredecessor(MachineBasicBlock *pred) {

2
test/CodeGen/X86/br-fold.ll
View File

@ -1,7 +1,7 @@
; RUN: llc -march=x86-64 < %s | FileCheck %s
; CHECK: orq
; CHECK-NEXT: LBB0_1
; CHECK-NEXT: %bb8.i329
@_ZN11xercesc_2_513SchemaSymbols21fgURI_SCHEMAFORSCHEMAE = external constant [33 x i16], align 32 ; <[33 x i16]*> [#uses=1]
@_ZN11xercesc_2_56XMLUni16fgNotationStringE = external constant [9 x i16], align 16 ; <[9 x i16]*> [#uses=1]