Coalesce stack slot accesses that arise when spilling both sides of a COPY.
This helps avoid silly code:
%R0<def = LOAD <fi#5>
STORE <fi#5>, %R0<kill>
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@110266 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/InlineSpiller.cpp b/lib/CodeGen/InlineSpiller.cpp
index d9dcbc0..872a829 100644
--- a/lib/CodeGen/InlineSpiller.cpp
+++ b/lib/CodeGen/InlineSpiller.cpp
@@ -85,6 +85,7 @@
bool reMaterializeFor(MachineBasicBlock::iterator MI);
void reMaterializeAll();
+ bool coalesceStackAccess(MachineInstr *MI);
bool foldMemoryOperand(MachineBasicBlock::iterator MI,
const SmallVectorImpl<unsigned> &Ops);
void insertReload(LiveInterval &NewLI, MachineBasicBlock::iterator MI);
@@ -291,6 +292,24 @@
}
}
+/// If MI is a load or store of stackSlot_, it can be removed.
+bool InlineSpiller::coalesceStackAccess(MachineInstr *MI) {
+ int FI = 0;
+ unsigned reg;
+ if (!(reg = tii_.isLoadFromStackSlot(MI, FI)) &&
+ !(reg = tii_.isStoreToStackSlot(MI, FI)))
+ return false;
+
+ // We have a stack access. Is it the right register and slot?
+ if (reg != li_->reg || FI != stackSlot_)
+ return false;
+
+ DEBUG(dbgs() << "Coalescing stack access: " << *MI);
+ lis_.RemoveMachineInstrFromMaps(MI);
+ MI->eraseFromParent();
+ return true;
+}
+
/// foldMemoryOperand - Try folding stack slot references in Ops into MI.
/// Return true on success, and MI will be erased.
bool InlineSpiller::foldMemoryOperand(MachineBasicBlock::iterator MI,
@@ -399,6 +418,10 @@
continue;
}
+ // Stack slot accesses may coalesce away.
+ if (coalesceStackAccess(MI))
+ continue;
+
// Analyze instruction.
bool Reads, Writes;
SmallVector<unsigned, 8> Ops;