Teach the inline spiller to attempt folding a load instruction into its single
use before rematerializing the load.
This allows us to produce:
addps LCPI0_1(%rip), %xmm2
Instead of:
movaps LCPI0_1(%rip), %xmm3
addps %xmm3, %xmm2
Saving a register and an instruction. The standard spiller already knows how to
do this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@122133 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index 462ca6d..443b2d0 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -85,7 +85,8 @@
bool coalesceStackAccess(MachineInstr *MI);
bool foldMemoryOperand(MachineBasicBlock::iterator MI,
- const SmallVectorImpl<unsigned> &Ops);
+ const SmallVectorImpl<unsigned> &Ops,
+ MachineInstr *LoadMI = 0);
void insertReload(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
void insertSpill(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
};
@@ -141,6 +142,14 @@
}
}
+ // Before rematerializing into a register for a single instruction, try to
+ // fold a load into the instruction. That avoids allocating a new register.
+ if (RM.OrigMI->getDesc().canFoldAsLoad() &&
+ foldMemoryOperand(MI, Ops, RM.OrigMI)) {
+ edit_->markRematerialized(RM.ParentVNI);
+ return true;
+ }
+
// Alocate a new register for the remat.
LiveInterval &NewLI = edit_->create(mri_, lis_, vrm_);
NewLI.markNotSpillable();
@@ -243,9 +252,13 @@
}
/// foldMemoryOperand - Try folding stack slot references in Ops into MI.
-/// Return true on success, and MI will be erased.
+/// @param MI Instruction using or defining the current register.
+/// @param Ops Operandices from readsWritesVirtualRegister().
+/// @param LoadMI Load instruction to use instead of stack slot when non-null.
+/// @return True on success, and MI will be erased.
bool InlineSpiller::foldMemoryOperand(MachineBasicBlock::iterator MI,
- const SmallVectorImpl<unsigned> &Ops) {
+ const SmallVectorImpl<unsigned> &Ops,
+ MachineInstr *LoadMI) {
// TargetInstrInfo::foldMemoryOperand only expects explicit, non-tied
// operands.
SmallVector<unsigned, 8> FoldOps;
@@ -262,11 +275,14 @@
FoldOps.push_back(Idx);
}
- MachineInstr *FoldMI = tii_.foldMemoryOperand(MI, FoldOps, stackSlot_);
+ MachineInstr *FoldMI =
+ LoadMI ? tii_.foldMemoryOperand(MI, FoldOps, LoadMI)
+ : tii_.foldMemoryOperand(MI, FoldOps, stackSlot_);
if (!FoldMI)
return false;
lis_.ReplaceMachineInstrInMaps(MI, FoldMI);
- vrm_.addSpillSlotUse(stackSlot_, FoldMI);
+ if (!LoadMI)
+ vrm_.addSpillSlotUse(stackSlot_, FoldMI);
MI->eraseFromParent();
DEBUG(dbgs() << "\tfolded: " << *FoldMI);
return true;