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GVN-hoist: compute DFS numbers once

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With this patch we compute the DFS numbers of instructions only once and update
them during the code generation when an instruction gets hoisted.

Differential Revision: https://reviews.llvm.org/D23021

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@277650 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Sebastian Pop 2016-08-03 20:54:36 +00:00
parent a9161e1912
commit c30fea992e
1 changed files with 22 additions and 12 deletions

34
lib/Transforms/Scalar/GVNHoist.cpp

@ -72,8 +72,16 @@ public:
//
// assert(A != B);
unsigned ADFS = DFSNumber.lookup(A);
unsigned BDFS = DFSNumber.lookup(B);
const BasicBlock *BA = A->getParent();
const BasicBlock *BB = B->getParent();
unsigned ADFS, BDFS;
if (BA == BB) {
ADFS = DFSNumber.lookup(A);
BDFS = DFSNumber.lookup(B);
} else {
ADFS = DFSNumber.lookup(BA);
BDFS = DFSNumber.lookup(BB);
}
assert (ADFS && BDFS);
return ADFS < BDFS;
}
@ -195,15 +203,17 @@ public:
bool Res = false;
MemorySSA M(F, AA, DT);
MSSA = &M;
// Perform DFS Numbering of instructions.
unsigned BBI = 0;
for (const BasicBlock *BB : depth_first(&F.getEntryBlock())) {
DFSNumber[BB] = ++BBI;
unsigned I = 0;
for (auto &Inst: *BB)
DFSNumber[&Inst] = ++I;
}
// FIXME: use lazy evaluation of VN to avoid the fix-point computation.
while (1) {
// Perform DFS Numbering of instructions.
unsigned I = 0;
for (const BasicBlock *BB : depth_first(&F.getEntryBlock()))
for (auto &Inst: *BB)
DFSNumber.insert({&Inst, ++I});
auto HoistStat = hoistExpressions(F);
if (HoistStat.first + HoistStat.second == 0)
return Res;
@ -215,9 +225,6 @@ public:
VN.clear();
Res = true;
// DFS numbers change when instructions are hoisted: clear and recompute.
DFSNumber.clear();
}
return Res;
@ -741,7 +748,10 @@ private:
continue;
// Move the instruction at the end of HoistPt.
Repl->moveBefore(HoistPt->getTerminator());
Instruction *Last = HoistPt->getTerminator();
Repl->moveBefore(Last);
DFSNumber[Repl] = DFSNumber[Last]++;
}
MemoryAccess *NewMemAcc = nullptr;