Look pass copies when determining whether hoisting would end up inserting more copies. rdar://9266679
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@129297 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 1c0f6ad..b315702 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -39,7 +39,6 @@
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
-
using namespace llvm;
STATISTIC(NumHoisted,
@@ -169,6 +168,10 @@
///
bool IsLoopInvariantInst(MachineInstr &I);
+ /// HasAnyPHIUse - Return true if the specified register is used by any
+ /// phi node.
+ bool HasAnyPHIUse(unsigned Reg) const;
+
/// HasHighOperandLatency - Compute operand latency between a def of 'Reg'
/// and an use in the current loop, return true if the target considered
/// it 'high'.
@@ -758,18 +761,25 @@
}
-/// HasPHIUses - Return true if the specified register has any PHI use.
-static bool HasPHIUses(unsigned Reg, MachineRegisterInfo *MRI) {
+/// HasAnyPHIUse - Return true if the specified register is used by any
+/// phi node.
+bool MachineLICM::HasAnyPHIUse(unsigned Reg) const {
for (MachineRegisterInfo::use_iterator UI = MRI->use_begin(Reg),
UE = MRI->use_end(); UI != UE; ++UI) {
MachineInstr *UseMI = &*UI;
if (UseMI->isPHI())
return true;
+ // Look pass copies as well.
+ if (UseMI->isCopy()) {
+ unsigned Def = UseMI->getOperand(0).getReg();
+ if (TargetRegisterInfo::isVirtualRegister(Def) &&
+ HasAnyPHIUse(Def))
+ return true;
+ }
}
return false;
}
-
/// HasHighOperandLatency - Compute operand latency between a def of 'Reg'
/// and an use in the current loop, return true if the target considered
/// it 'high'.
@@ -976,14 +986,13 @@
return false;
}
- // If result(s) of this instruction is used by PHIs, then don't hoist it.
- // The presence of joins makes it difficult for current register allocator
- // implementation to perform remat.
+ // If result(s) of this instruction is used by PHIs outside of the loop, then
+ // don't hoist it if the instruction because it will introduce an extra copy.
for (unsigned i = 0, e = MI.getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI.getOperand(i);
if (!MO.isReg() || !MO.isDef())
continue;
- if (HasPHIUses(MO.getReg(), MRI))
+ if (HasAnyPHIUse(MO.getReg()))
return false;
}