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-rw-r--r--contrib/llvm/lib/CodeGen/MachineSink.cpp182
1 files changed, 121 insertions, 61 deletions
diff --git a/contrib/llvm/lib/CodeGen/MachineSink.cpp b/contrib/llvm/lib/CodeGen/MachineSink.cpp
index 29cfb49..1ce546b 100644
--- a/contrib/llvm/lib/CodeGen/MachineSink.cpp
+++ b/contrib/llvm/lib/CodeGen/MachineSink.cpp
@@ -32,7 +32,7 @@
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
-static cl::opt<bool>
+static cl::opt<bool>
SplitEdges("machine-sink-split",
cl::desc("Split critical edges during machine sinking"),
cl::init(true), cl::Hidden);
@@ -90,12 +90,19 @@ namespace {
bool AllUsesDominatedByBlock(unsigned Reg, MachineBasicBlock *MBB,
MachineBasicBlock *DefMBB,
bool &BreakPHIEdge, bool &LocalUse) const;
+ MachineBasicBlock *FindSuccToSinkTo(MachineInstr *MI, MachineBasicBlock *MBB,
+ bool &BreakPHIEdge);
+ bool isProfitableToSinkTo(unsigned Reg, MachineInstr *MI,
+ MachineBasicBlock *MBB,
+ MachineBasicBlock *SuccToSinkTo);
+
bool PerformTrivialForwardCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB);
};
} // end anonymous namespace
char MachineSinking::ID = 0;
+char &llvm::MachineSinkingID = MachineSinking::ID;
INITIALIZE_PASS_BEGIN(MachineSinking, "machine-sink",
"Machine code sinking", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
@@ -104,8 +111,6 @@ INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
INITIALIZE_PASS_END(MachineSinking, "machine-sink",
"Machine code sinking", false, false)
-FunctionPass *llvm::createMachineSinkingPass() { return new MachineSinking(); }
-
bool MachineSinking::PerformTrivialForwardCoalescing(MachineInstr *MI,
MachineBasicBlock *MBB) {
if (!MI->isCopy())
@@ -147,14 +152,10 @@ MachineSinking::AllUsesDominatedByBlock(unsigned Reg,
assert(TargetRegisterInfo::isVirtualRegister(Reg) &&
"Only makes sense for vregs");
+ // Ignore debug uses because debug info doesn't affect the code.
if (MRI->use_nodbg_empty(Reg))
return true;
- // Ignoring debug uses is necessary so debug info doesn't affect the code.
- // This may leave a referencing dbg_value in the original block, before
- // the definition of the vreg. Dwarf generator handles this although the
- // user might not get the right info at runtime.
-
// BreakPHIEdge is true if all the uses are in the successor MBB being sunken
// into and they are all PHI nodes. In this case, machine-sink must break
// the critical edge first. e.g.
@@ -291,7 +292,7 @@ bool MachineSinking::isWorthBreakingCriticalEdge(MachineInstr *MI,
if (!CEBCandidates.insert(std::make_pair(From, To)))
return true;
- if (!MI->isCopy() && !MI->getDesc().isAsCheapAsAMove())
+ if (!MI->isCopy() && !MI->isAsCheapAsAMove())
return true;
// MI is cheap, we probably don't want to break the critical edge for it.
@@ -382,9 +383,9 @@ static bool AvoidsSinking(MachineInstr *MI, MachineRegisterInfo *MRI) {
return MI->isInsertSubreg() || MI->isSubregToReg() || MI->isRegSequence();
}
-/// collectDebgValues - Scan instructions following MI and collect any
+/// collectDebgValues - Scan instructions following MI and collect any
/// matching DBG_VALUEs.
-static void collectDebugValues(MachineInstr *MI,
+static void collectDebugValues(MachineInstr *MI,
SmallVector<MachineInstr *, 2> & DbgValues) {
DbgValues.clear();
if (!MI->getOperand(0).isReg())
@@ -401,35 +402,76 @@ static void collectDebugValues(MachineInstr *MI,
}
}
-/// SinkInstruction - Determine whether it is safe to sink the specified machine
-/// instruction out of its current block into a successor.
-bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
- // Don't sink insert_subreg, subreg_to_reg, reg_sequence. These are meant to
- // be close to the source to make it easier to coalesce.
- if (AvoidsSinking(MI, MRI))
+/// isPostDominatedBy - Return true if A is post dominated by B.
+static bool isPostDominatedBy(MachineBasicBlock *A, MachineBasicBlock *B) {
+
+ // FIXME - Use real post dominator.
+ if (A->succ_size() != 2)
+ return false;
+ MachineBasicBlock::succ_iterator I = A->succ_begin();
+ if (B == *I)
+ ++I;
+ MachineBasicBlock *OtherSuccBlock = *I;
+ if (OtherSuccBlock->succ_size() != 1 ||
+ *(OtherSuccBlock->succ_begin()) != B)
return false;
- // Check if it's safe to move the instruction.
- if (!MI->isSafeToMove(TII, AA, SawStore))
+ return true;
+}
+
+/// isProfitableToSinkTo - Return true if it is profitable to sink MI.
+bool MachineSinking::isProfitableToSinkTo(unsigned Reg, MachineInstr *MI,
+ MachineBasicBlock *MBB,
+ MachineBasicBlock *SuccToSinkTo) {
+ assert (MI && "Invalid MachineInstr!");
+ assert (SuccToSinkTo && "Invalid SinkTo Candidate BB");
+
+ if (MBB == SuccToSinkTo)
return false;
- // FIXME: This should include support for sinking instructions within the
- // block they are currently in to shorten the live ranges. We often get
- // instructions sunk into the top of a large block, but it would be better to
- // also sink them down before their first use in the block. This xform has to
- // be careful not to *increase* register pressure though, e.g. sinking
- // "x = y + z" down if it kills y and z would increase the live ranges of y
- // and z and only shrink the live range of x.
+ // It is profitable if SuccToSinkTo does not post dominate current block.
+ if (!isPostDominatedBy(MBB, SuccToSinkTo))
+ return true;
+
+ // Check if only use in post dominated block is PHI instruction.
+ bool NonPHIUse = false;
+ for (MachineRegisterInfo::use_nodbg_iterator
+ I = MRI->use_nodbg_begin(Reg), E = MRI->use_nodbg_end();
+ I != E; ++I) {
+ MachineInstr *UseInst = &*I;
+ MachineBasicBlock *UseBlock = UseInst->getParent();
+ if (UseBlock == SuccToSinkTo && !UseInst->isPHI())
+ NonPHIUse = true;
+ }
+ if (!NonPHIUse)
+ return true;
+
+ // If SuccToSinkTo post dominates then also it may be profitable if MI
+ // can further profitably sinked into another block in next round.
+ bool BreakPHIEdge = false;
+ // FIXME - If finding successor is compile time expensive then catch results.
+ if (MachineBasicBlock *MBB2 = FindSuccToSinkTo(MI, SuccToSinkTo, BreakPHIEdge))
+ return isProfitableToSinkTo(Reg, MI, SuccToSinkTo, MBB2);
+
+ // If SuccToSinkTo is final destination and it is a post dominator of current
+ // block then it is not profitable to sink MI into SuccToSinkTo block.
+ return false;
+}
+
+/// FindSuccToSinkTo - Find a successor to sink this instruction to.
+MachineBasicBlock *MachineSinking::FindSuccToSinkTo(MachineInstr *MI,
+ MachineBasicBlock *MBB,
+ bool &BreakPHIEdge) {
+
+ assert (MI && "Invalid MachineInstr!");
+ assert (MBB && "Invalid MachineBasicBlock!");
// Loop over all the operands of the specified instruction. If there is
// anything we can't handle, bail out.
- MachineBasicBlock *ParentBlock = MI->getParent();
// SuccToSinkTo - This is the successor to sink this instruction to, once we
// decide.
MachineBasicBlock *SuccToSinkTo = 0;
-
- bool BreakPHIEdge = false;
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isReg()) continue; // Ignore non-register operands.
@@ -442,24 +484,11 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// If the physreg has no defs anywhere, it's just an ambient register
// and we can freely move its uses. Alternatively, if it's allocatable,
// it could get allocated to something with a def during allocation.
- if (!MRI->def_empty(Reg))
- return false;
-
- if (AllocatableSet.test(Reg))
- return false;
-
- // Check for a def among the register's aliases too.
- for (const unsigned *Alias = TRI->getAliasSet(Reg); *Alias; ++Alias) {
- unsigned AliasReg = *Alias;
- if (!MRI->def_empty(AliasReg))
- return false;
-
- if (AllocatableSet.test(AliasReg))
- return false;
- }
+ if (!MRI->isConstantPhysReg(Reg, *MBB->getParent()))
+ return NULL;
} else if (!MO.isDead()) {
// A def that isn't dead. We can't move it.
- return false;
+ return NULL;
}
} else {
// Virtual register uses are always safe to sink.
@@ -467,7 +496,7 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// If it's not safe to move defs of the register class, then abort.
if (!TII->isSafeToMoveRegClassDefs(MRI->getRegClass(Reg)))
- return false;
+ return NULL;
// FIXME: This picks a successor to sink into based on having one
// successor that dominates all the uses. However, there are cases where
@@ -488,48 +517,79 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
// If a previous operand picked a block to sink to, then this operand
// must be sinkable to the same block.
bool LocalUse = false;
- if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo, ParentBlock,
+ if (!AllUsesDominatedByBlock(Reg, SuccToSinkTo, MBB,
BreakPHIEdge, LocalUse))
- return false;
+ return NULL;
continue;
}
// Otherwise, we should look at all the successors and decide which one
// we should sink to.
- for (MachineBasicBlock::succ_iterator SI = ParentBlock->succ_begin(),
- E = ParentBlock->succ_end(); SI != E; ++SI) {
+ for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
+ E = MBB->succ_end(); SI != E; ++SI) {
+ MachineBasicBlock *SuccBlock = *SI;
bool LocalUse = false;
- if (AllUsesDominatedByBlock(Reg, *SI, ParentBlock,
+ if (AllUsesDominatedByBlock(Reg, SuccBlock, MBB,
BreakPHIEdge, LocalUse)) {
- SuccToSinkTo = *SI;
+ SuccToSinkTo = SuccBlock;
break;
}
if (LocalUse)
// Def is used locally, it's never safe to move this def.
- return false;
+ return NULL;
}
// If we couldn't find a block to sink to, ignore this instruction.
if (SuccToSinkTo == 0)
- return false;
+ return NULL;
+ else if (!isProfitableToSinkTo(Reg, MI, MBB, SuccToSinkTo))
+ return NULL;
}
}
- // If there are no outputs, it must have side-effects.
- if (SuccToSinkTo == 0)
- return false;
+ // It is not possible to sink an instruction into its own block. This can
+ // happen with loops.
+ if (MBB == SuccToSinkTo)
+ return NULL;
// It's not safe to sink instructions to EH landing pad. Control flow into
// landing pad is implicitly defined.
- if (SuccToSinkTo->isLandingPad())
+ if (SuccToSinkTo && SuccToSinkTo->isLandingPad())
+ return NULL;
+
+ return SuccToSinkTo;
+}
+
+/// SinkInstruction - Determine whether it is safe to sink the specified machine
+/// instruction out of its current block into a successor.
+bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) {
+ // Don't sink insert_subreg, subreg_to_reg, reg_sequence. These are meant to
+ // be close to the source to make it easier to coalesce.
+ if (AvoidsSinking(MI, MRI))
return false;
- // It is not possible to sink an instruction into its own block. This can
- // happen with loops.
- if (MI->getParent() == SuccToSinkTo)
+ // Check if it's safe to move the instruction.
+ if (!MI->isSafeToMove(TII, AA, SawStore))
return false;
+ // FIXME: This should include support for sinking instructions within the
+ // block they are currently in to shorten the live ranges. We often get
+ // instructions sunk into the top of a large block, but it would be better to
+ // also sink them down before their first use in the block. This xform has to
+ // be careful not to *increase* register pressure though, e.g. sinking
+ // "x = y + z" down if it kills y and z would increase the live ranges of y
+ // and z and only shrink the live range of x.
+
+ bool BreakPHIEdge = false;
+ MachineBasicBlock *ParentBlock = MI->getParent();
+ MachineBasicBlock *SuccToSinkTo = FindSuccToSinkTo(MI, ParentBlock, BreakPHIEdge);
+
+ // If there are no outputs, it must have side-effects.
+ if (SuccToSinkTo == 0)
+ return false;
+
+
// If the instruction to move defines a dead physical register which is live
// when leaving the basic block, don't move it because it could turn into a
// "zombie" define of that preg. E.g., EFLAGS. (<rdar://problem/8030636>)
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