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[CodeGen] Untangle RegisterCoalescer from LRE's ScannedRemattable flag [nfc[ #159839

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Merged
merged 1 commit into from
Sep 20, 2025
Merged

[CodeGen] Untangle RegisterCoalescer from LRE's ScannedRemattable flag [nfc[ #159839

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8 changes: 2 additions & 6 deletions llvm/include/llvm/CodeGen/LiveRangeEdit.h
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Original file line number Diff line number Diff line change
Expand Up @@ -176,14 +176,10 @@ class LiveRangeEdit : private MachineRegisterInfo::Delegate {
Register create() { return createFrom(getReg()); }

/// anyRematerializable - Return true if any parent values may be
/// rematerializable.
/// This function must be called before any rematerialization is attempted.
/// rematerializable. This function must be called before
/// canRematerializeAt is called..
bool anyRematerializable();

/// checkRematerializable - Manually add VNI to the list of rematerializable
/// values if DefMI may be rematerializable.
bool checkRematerializable(VNInfo *VNI, const MachineInstr *DefMI);

/// Remat - Information needed to rematerialize at a specific location.
struct Remat {
const VNInfo *const ParentVNI; // parent_'s value at the remat location.
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13 changes: 2 additions & 11 deletions llvm/lib/CodeGen/LiveRangeEdit.cpp
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Expand Up @@ -68,16 +68,6 @@ Register LiveRangeEdit::createFrom(Register OldReg) {
return VReg;
}

bool LiveRangeEdit::checkRematerializable(VNInfo *VNI,
const MachineInstr *DefMI) {
assert(DefMI && "Missing instruction");
ScannedRemattable = true;
if (!TII.isTriviallyReMaterializable(*DefMI))
return false;
Remattable.insert(VNI);
return true;
}

void LiveRangeEdit::scanRemattable() {
for (VNInfo *VNI : getParent().valnos) {
if (VNI->isUnused())
Expand All @@ -90,7 +80,8 @@ void LiveRangeEdit::scanRemattable() {
MachineInstr *DefMI = LIS.getInstructionFromIndex(OrigVNI->def);
if (!DefMI)
continue;
checkRematerializable(OrigVNI, DefMI);
if (TII.isTriviallyReMaterializable(*DefMI))
Remattable.insert(OrigVNI);
}
ScannedRemattable = true;
}
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13 changes: 7 additions & 6 deletions llvm/lib/CodeGen/RegisterCoalescer.cpp
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Expand Up @@ -1325,9 +1325,7 @@ bool RegisterCoalescer::reMaterializeTrivialDef(const CoalescerPair &CP,
if (!TII->isAsCheapAsAMove(*DefMI))
return false;

SmallVector<Register, 8> NewRegs;
LiveRangeEdit Edit(&SrcInt, NewRegs, *MF, *LIS, nullptr, this);
if (!Edit.checkRematerializable(ValNo, DefMI))
if (!TII->isTriviallyReMaterializable(*DefMI))
return false;

if (!definesFullReg(*DefMI, SrcReg))
Expand Down Expand Up @@ -1395,15 +1393,18 @@ bool RegisterCoalescer::reMaterializeTrivialDef(const CoalescerPair &CP,
}
}

LiveRangeEdit::Remat RM(ValNo);
RM.OrigMI = DefMI;
if (!Edit.canRematerializeAt(RM, ValNo, CopyIdx))
SmallVector<Register, 8> NewRegs;
LiveRangeEdit Edit(&SrcInt, NewRegs, *MF, *LIS, nullptr, this);
SlotIndex DefIdx = LIS->getInstructionIndex(*DefMI);
if (!Edit.allUsesAvailableAt(DefMI, DefIdx, CopyIdx))
return false;

DebugLoc DL = CopyMI->getDebugLoc();
MachineBasicBlock *MBB = CopyMI->getParent();
MachineBasicBlock::iterator MII =
std::next(MachineBasicBlock::iterator(CopyMI));
LiveRangeEdit::Remat RM(ValNo);
RM.OrigMI = DefMI;
Edit.rematerializeAt(*MBB, MII, DstReg, RM, *TRI, false, SrcIdx, CopyMI);
MachineInstr &NewMI = *std::prev(MII);
NewMI.setDebugLoc(DL);
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