[llvm] 34f4fe3 - [NFC][Regalloc] Ensure Query::interferingVRegs is accurate.
Mircea Trofin via llvm-commits
llvm-commits at lists.llvm.org
Tue Nov 2 18:27:02 PDT 2021
Author: Mircea Trofin
Date: 2021-11-02T18:26:54-07:00
New Revision: 34f4fe3a9009d4443ff166a36d7ddb07e3ebb512
URL: https://github.com/llvm/llvm-project/commit/34f4fe3a9009d4443ff166a36d7ddb07e3ebb512
DIFF: https://github.com/llvm/llvm-project/commit/34f4fe3a9009d4443ff166a36d7ddb07e3ebb512.diff
LOG: [NFC][Regalloc] Ensure Query::interferingVRegs is accurate.
To correctly use Query, one had to first call collectInterferingVRegs to
pre-cache the query result, then call interferingVRegs. Failing the
former, interferingVRegs could be stale. This did cause a bug which was
addressed in D98232, but the underlying usability issue of the Query API
wasn't.
This patch addresses the latter by making collectInterferingVRegs an
implementation detail, and having interferingVRegs play both roles. One
side-effect of this is that interferingVRegs is not const anymore.
Differential Revision: https://reviews.llvm.org/D112882
Added:
Modified:
llvm/include/llvm/CodeGen/LiveIntervalUnion.h
llvm/lib/CodeGen/LiveIntervalUnion.cpp
llvm/lib/CodeGen/RegAllocBasic.cpp
llvm/lib/CodeGen/RegAllocGreedy.cpp
Removed:
################################################################################
diff --git a/llvm/include/llvm/CodeGen/LiveIntervalUnion.h b/llvm/include/llvm/CodeGen/LiveIntervalUnion.h
index 4ebe0f2dcfd88..3b6a4a379d720 100644
--- a/llvm/include/llvm/CodeGen/LiveIntervalUnion.h
+++ b/llvm/include/llvm/CodeGen/LiveIntervalUnion.h
@@ -114,12 +114,19 @@ class LiveIntervalUnion {
const LiveRange *LR = nullptr;
LiveRange::const_iterator LRI; ///< current position in LR
ConstSegmentIter LiveUnionI; ///< current position in LiveUnion
- Optional<SmallVector<LiveInterval *, 4>> InterferingVRegs;
+ SmallVector<LiveInterval *, 4> InterferingVRegs;
bool CheckedFirstInterference = false;
bool SeenAllInterferences = false;
unsigned Tag = 0;
unsigned UserTag = 0;
+ // Count the virtual registers in this union that interfere with this
+ // query's live virtual register, up to maxInterferingRegs.
+ unsigned collectInterferingVRegs(unsigned MaxInterferingRegs);
+
+ // Was this virtual register visited during collectInterferingVRegs?
+ bool isSeenInterference(LiveInterval *VirtReg) const;
+
public:
Query() = default;
Query(const LiveRange &LR, const LiveIntervalUnion &LIU)
@@ -131,7 +138,7 @@ class LiveIntervalUnion {
const LiveIntervalUnion &NewLiveUnion) {
LiveUnion = &NewLiveUnion;
LR = &NewLR;
- InterferingVRegs = None;
+ InterferingVRegs.clear();
CheckedFirstInterference = false;
SeenAllInterferences = false;
Tag = NewLiveUnion.getTag();
@@ -151,20 +158,12 @@ class LiveIntervalUnion {
// Does this live virtual register interfere with the union?
bool checkInterference() { return collectInterferingVRegs(1); }
- // Count the virtual registers in this union that interfere with this
- // query's live virtual register, up to maxInterferingRegs.
- unsigned collectInterferingVRegs(
- unsigned MaxInterferingRegs = std::numeric_limits<unsigned>::max());
-
- // Was this virtual register visited during collectInterferingVRegs?
- bool isSeenInterference(LiveInterval *VirtReg) const;
-
- // Did collectInterferingVRegs collect all interferences?
- bool seenAllInterferences() const { return SeenAllInterferences; }
-
// Vector generated by collectInterferingVRegs.
- const SmallVectorImpl<LiveInterval*> &interferingVRegs() const {
- return *InterferingVRegs;
+ const SmallVectorImpl<LiveInterval *> &interferingVRegs(
+ unsigned MaxInterferingRegs = std::numeric_limits<unsigned>::max()) {
+ if (!SeenAllInterferences || MaxInterferingRegs < InterferingVRegs.size())
+ collectInterferingVRegs(MaxInterferingRegs);
+ return InterferingVRegs;
}
};
diff --git a/llvm/lib/CodeGen/LiveIntervalUnion.cpp b/llvm/lib/CodeGen/LiveIntervalUnion.cpp
index dfa523d4bf41c..50b31e1eb247b 100644
--- a/llvm/lib/CodeGen/LiveIntervalUnion.cpp
+++ b/llvm/lib/CodeGen/LiveIntervalUnion.cpp
@@ -112,7 +112,7 @@ LiveInterval *LiveIntervalUnion::getOneVReg() const {
// Scan the vector of interfering virtual registers in this union. Assume it's
// quite small.
bool LiveIntervalUnion::Query::isSeenInterference(LiveInterval *VirtReg) const {
- return is_contained(*InterferingVRegs, VirtReg);
+ return is_contained(InterferingVRegs, VirtReg);
}
// Collect virtual registers in this union that interfere with this
@@ -124,14 +124,11 @@ bool LiveIntervalUnion::Query::isSeenInterference(LiveInterval *VirtReg) const {
// 2. SeenAllInterferences == true: InterferingVRegs complete, iterators unused.
// 3. Iterators left at the last seen intersection.
//
-unsigned LiveIntervalUnion::Query::
-collectInterferingVRegs(unsigned MaxInterferingRegs) {
- if (!InterferingVRegs)
- InterferingVRegs.emplace();
-
+unsigned
+LiveIntervalUnion::Query::collectInterferingVRegs(unsigned MaxInterferingRegs) {
// Fast path return if we already have the desired information.
- if (SeenAllInterferences || InterferingVRegs->size() >= MaxInterferingRegs)
- return InterferingVRegs->size();
+ if (SeenAllInterferences || InterferingVRegs.size() >= MaxInterferingRegs)
+ return InterferingVRegs.size();
// Set up iterators on the first call.
if (!CheckedFirstInterference) {
@@ -160,14 +157,14 @@ collectInterferingVRegs(unsigned MaxInterferingRegs) {
LiveInterval *VReg = LiveUnionI.value();
if (VReg != RecentReg && !isSeenInterference(VReg)) {
RecentReg = VReg;
- InterferingVRegs->push_back(VReg);
- if (InterferingVRegs->size() >= MaxInterferingRegs)
- return InterferingVRegs->size();
+ InterferingVRegs.push_back(VReg);
+ if (InterferingVRegs.size() >= MaxInterferingRegs)
+ return InterferingVRegs.size();
}
// This LiveUnion segment is no longer interesting.
if (!(++LiveUnionI).valid()) {
SeenAllInterferences = true;
- return InterferingVRegs->size();
+ return InterferingVRegs.size();
}
}
@@ -188,7 +185,7 @@ collectInterferingVRegs(unsigned MaxInterferingRegs) {
LiveUnionI.advanceTo(LRI->start);
}
SeenAllInterferences = true;
- return InterferingVRegs->size();
+ return InterferingVRegs.size();
}
void LiveIntervalUnion::Array::init(LiveIntervalUnion::Allocator &Alloc,
diff --git a/llvm/lib/CodeGen/RegAllocBasic.cpp b/llvm/lib/CodeGen/RegAllocBasic.cpp
index b65d580779581..a9816b13e7980 100644
--- a/llvm/lib/CodeGen/RegAllocBasic.cpp
+++ b/llvm/lib/CodeGen/RegAllocBasic.cpp
@@ -217,9 +217,7 @@ bool RABasic::spillInterferences(LiveInterval &VirtReg, MCRegister PhysReg,
// Collect interferences assigned to any alias of the physical register.
for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
- Q.collectInterferingVRegs();
- for (unsigned i = Q.interferingVRegs().size(); i; --i) {
- LiveInterval *Intf = Q.interferingVRegs()[i - 1];
+ for (auto *Intf : reverse(Q.interferingVRegs())) {
if (!Intf->isSpillable() || Intf->weight() > VirtReg.weight())
return false;
Intfs.push_back(Intf);
diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
index 3f58afca47470..0e4e23f61587e 100644
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -955,11 +955,12 @@ bool RAGreedy::canEvictInterference(
for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
// If there is 10 or more interferences, chances are one is heavier.
- if (Q.collectInterferingVRegs(10) >= 10)
+ const auto &Interferences = Q.interferingVRegs(10);
+ if (Interferences.size() >= 10)
return false;
// Check if any interfering live range is heavier than MaxWeight.
- for (LiveInterval *Intf : reverse(Q.interferingVRegs())) {
+ for (LiveInterval *Intf : reverse(Interferences)) {
assert(Register::isVirtualRegister(Intf->reg()) &&
"Only expecting virtual register interference from query");
@@ -1037,7 +1038,6 @@ bool RAGreedy::canEvictInterferenceInRange(const LiveInterval &VirtReg,
for (MCRegUnitIterator Units(PhysReg, TRI); Units.isValid(); ++Units) {
LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
- Q.collectInterferingVRegs();
// Check if any interfering live range is heavier than MaxWeight.
for (const LiveInterval *Intf : reverse(Q.interferingVRegs())) {
@@ -1127,7 +1127,6 @@ void RAGreedy::evictInterference(LiveInterval &VirtReg, MCRegister PhysReg,
// should be fast, we may need to recalculate if when
diff erent physregs
// overlap the same register unit so we had
diff erent SubRanges queried
// against it.
- Q.collectInterferingVRegs();
ArrayRef<LiveInterval*> IVR = Q.interferingVRegs();
Intfs.append(IVR.begin(), IVR.end());
}
@@ -2547,8 +2546,9 @@ bool RAGreedy::mayRecolorAllInterferences(
LiveIntervalUnion::Query &Q = Matrix->query(VirtReg, *Units);
// If there is LastChanceRecoloringMaxInterference or more interferences,
// chances are one would not be recolorable.
- if (Q.collectInterferingVRegs(LastChanceRecoloringMaxInterference) >=
- LastChanceRecoloringMaxInterference && !ExhaustiveSearch) {
+ if (Q.interferingVRegs(LastChanceRecoloringMaxInterference).size() >=
+ LastChanceRecoloringMaxInterference &&
+ !ExhaustiveSearch) {
LLVM_DEBUG(dbgs() << "Early abort: too many interferences.\n");
CutOffInfo |= CO_Interf;
return false;
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