Allow some reloads to be folded in multi-use cases. Specifically testl r, r -> cmpl [mem], 0.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44479 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveIntervalAnalysis.cpp b/lib/CodeGen/LiveIntervalAnalysis.cpp
index f902f4b..2b22faf 100644
--- a/lib/CodeGen/LiveIntervalAnalysis.cpp
+++ b/lib/CodeGen/LiveIntervalAnalysis.cpp
@@ -644,20 +644,27 @@
bool LiveIntervals::tryFoldMemoryOperand(MachineInstr* &MI,
VirtRegMap &vrm, MachineInstr *DefMI,
unsigned InstrIdx, unsigned OpIdx,
- unsigned NumUses,
+ SmallVector<unsigned, 2> &UseOps,
bool isSS, int Slot, unsigned Reg) {
// FIXME: fold subreg use
if (MI->getOperand(OpIdx).getSubReg())
return false;
- // FIXME: It may be possible to fold load when there are multiple uses.
- // e.g. On x86, TEST32rr r, r -> CMP32rm [mem], 0
- if (NumUses > 1)
- return false;
+ MachineInstr *fmi = NULL;
- MachineInstr *fmi = isSS
- ? mri_->foldMemoryOperand(MI, OpIdx, Slot)
- : mri_->foldMemoryOperand(MI, OpIdx, DefMI);
+ if (UseOps.size() < 2)
+ fmi = isSS ? mri_->foldMemoryOperand(MI, OpIdx, Slot)
+ : mri_->foldMemoryOperand(MI, OpIdx, DefMI);
+ else {
+ if (OpIdx != UseOps[0])
+ // Must be two-address instruction + one more use. Not going to fold.
+ return false;
+ // It may be possible to fold load when there are multiple uses.
+ // e.g. On x86, TEST32rr r, r -> CMP32rm [mem], 0
+ fmi = isSS ? mri_->foldMemoryOperand(MI, UseOps, Slot)
+ : mri_->foldMemoryOperand(MI, UseOps, DefMI);
+ }
+
if (fmi) {
// Attempt to fold the memory reference into the instruction. If
// we can do this, we don't need to insert spill code.
@@ -768,7 +775,9 @@
HasUse = mop.isUse();
HasDef = mop.isDef();
- unsigned NumUses = HasUse;
+ SmallVector<unsigned, 2> UseOps;
+ if (HasUse)
+ UseOps.push_back(i);
std::vector<unsigned> UpdateOps;
for (unsigned j = i+1, e = MI->getNumOperands(); j != e; ++j) {
if (!MI->getOperand(j).isRegister())
@@ -779,7 +788,7 @@
if (RegJ == RegI) {
UpdateOps.push_back(j);
if (MI->getOperand(j).isUse())
- ++NumUses;
+ UseOps.push_back(j);
HasUse |= MI->getOperand(j).isUse();
HasDef |= MI->getOperand(j).isDef();
}
@@ -787,7 +796,7 @@
if (TryFold &&
tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index, i,
- NumUses, FoldSS, FoldSlot, Reg)) {
+ UseOps, FoldSS, FoldSlot, Reg)) {
// Folding the load/store can completely change the instruction in
// unpredictable ways, rescan it from the beginning.
HasUse = false;
@@ -1207,6 +1216,7 @@
if (!TrySplit)
return NewLIs;
+ SmallVector<unsigned, 2> UseOps;
if (NeedStackSlot) {
int Id = SpillMBBs.find_first();
while (Id != -1) {
@@ -1217,7 +1227,7 @@
bool isReMat = vrm.isReMaterialized(VReg);
MachineInstr *MI = getInstructionFromIndex(index);
int OpIdx = -1;
- unsigned NumUses = 0;
+ UseOps.clear();
if (spills[i].canFold) {
for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
MachineOperand &MO = MI->getOperand(j);
@@ -1230,20 +1240,20 @@
// Can't fold if it's two-address code and the use isn't the
// first and only use.
if (isReMat ||
- (NumUses == 0 && !alsoFoldARestore(Id, index, VReg, RestoreMBBs,
- RestoreIdxes))) {
+ (UseOps.empty() && !alsoFoldARestore(Id, index, VReg,
+ RestoreMBBs, RestoreIdxes))) {
OpIdx = -1;
break;
}
- ++NumUses;
+ UseOps.push_back(j);
}
}
// Fold the store into the def if possible.
bool Folded = false;
if (OpIdx != -1) {
- if (tryFoldMemoryOperand(MI, vrm, NULL, index, OpIdx, NumUses,
+ if (tryFoldMemoryOperand(MI, vrm, NULL, index, OpIdx, UseOps,
true, Slot, VReg)) {
- if (NumUses)
+ if (!UseOps.empty())
// Folded a two-address instruction, do not issue a load.
eraseRestoreInfo(Id, index, VReg, RestoreMBBs, RestoreIdxes);
Folded = true;
@@ -1267,8 +1277,8 @@
continue;
unsigned VReg = restores[i].vreg;
MachineInstr *MI = getInstructionFromIndex(index);
- unsigned NumUses = 0;
int OpIdx = -1;
+ UseOps.clear();
if (restores[i].canFold) {
for (unsigned j = 0, ee = MI->getNumOperands(); j != ee; ++j) {
MachineOperand &MO = MI->getOperand(j);
@@ -1280,10 +1290,10 @@
OpIdx = -1;
break;
}
- if (NumUses == 0)
+ if (UseOps.empty())
// Use the first use index.
OpIdx = (int)j;
- ++NumUses;
+ UseOps.push_back(j);
}
}
@@ -1298,9 +1308,9 @@
if (isLoadSS ||
(ReMatDefMI->getInstrDescriptor()->Flags & M_LOAD_FLAG))
Folded = tryFoldMemoryOperand(MI, vrm, ReMatDefMI, index, OpIdx,
- NumUses, isLoadSS, LdSlot, VReg);
+ UseOps, isLoadSS, LdSlot, VReg);
} else
- Folded = tryFoldMemoryOperand(MI, vrm, NULL, index, OpIdx, NumUses,
+ Folded = tryFoldMemoryOperand(MI, vrm, NULL, index, OpIdx, UseOps,
true, Slot, VReg);
}
// If folding is not possible / failed, then tell the spiller to issue a