Replace TargetInstrInfo::isInvariantLoad and its target-specific
implementations with a new MachineInstr::isInvariantLoad, which uses
MachineMemOperands and is target-independent. This brings MachineLICM
and other functionality to targets which previously lacked an
isInvariantLoad implementation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83475 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index a3560a7..2dc99f5 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -24,6 +24,7 @@
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetInstrDesc.h"
#include "llvm/Target/TargetRegisterInfo.h"
+#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/Analysis/DebugInfo.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LeakDetector.h"
@@ -946,7 +947,7 @@
// destination. The check for isInvariantLoad gives the targe the chance to
// classify the load as always returning a constant, e.g. a constant pool
// load.
- if (TID->mayLoad() && !TII->isInvariantLoad(this))
+ if (TID->mayLoad() && !isInvariantLoad())
// Otherwise, this is a real load. If there is a store between the load and
// end of block, or if the load is volatile, we can't move it.
return !SawStore && !hasVolatileMemoryRef();
@@ -1005,6 +1006,46 @@
return false;
}
+/// isInvariantLoad - Return true if this instruction is loading from a
+/// location whose value is invariant across the function. For example,
+/// loading a value from the constant pool or from from the argument area
+/// of a function if it does not change. This should only return true of
+/// *all* loads the instruction does are invariant (if it does multiple loads).
+bool MachineInstr::isInvariantLoad(AliasAnalysis *AA) const {
+ // If the instruction doesn't load at all, it isn't an invariant load.
+ if (!TID->mayLoad())
+ return false;
+
+ // If the instruction has lost its memoperands, conservatively assume that
+ // it may not be an invariant load.
+ if (memoperands_empty())
+ return false;
+
+ const MachineFrameInfo *MFI = getParent()->getParent()->getFrameInfo();
+
+ for (mmo_iterator I = memoperands_begin(),
+ E = memoperands_end(); I != E; ++I) {
+ if ((*I)->isVolatile()) return false;
+ if ((*I)->isStore()) return false;
+
+ if (const Value *V = (*I)->getValue()) {
+ // A load from a constant PseudoSourceValue is invariant.
+ if (const PseudoSourceValue *PSV = dyn_cast<PseudoSourceValue>(V))
+ if (PSV->isConstant(MFI))
+ continue;
+ // If we have an AliasAnalysis, ask it whether the memory is constant.
+ if (AA && AA->pointsToConstantMemory(V))
+ continue;
+ }
+
+ // Otherwise assume conservatively.
+ return false;
+ }
+
+ // Everything checks out.
+ return true;
+}
+
void MachineInstr::dump() const {
errs() << " " << *this;
}
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 61678f1..b5827aa 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -28,6 +28,7 @@
#include "llvm/Target/TargetRegisterInfo.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Compiler.h"
@@ -47,6 +48,7 @@
BitVector AllocatableSet;
// Various analyses that we use...
+ AliasAnalysis *AA; // Alias analysis info.
MachineLoopInfo *LI; // Current MachineLoopInfo
MachineDominatorTree *DT; // Machine dominator tree for the cur loop
MachineRegisterInfo *RegInfo; // Machine register information
@@ -72,6 +74,7 @@
AU.setPreservesCFG();
AU.addRequired<MachineLoopInfo>();
AU.addRequired<MachineDominatorTree>();
+ AU.addRequired<AliasAnalysis>();
AU.addPreserved<MachineLoopInfo>();
AU.addPreserved<MachineDominatorTree>();
MachineFunctionPass::getAnalysisUsage(AU);
@@ -144,6 +147,7 @@
// Get our Loop information...
LI = &getAnalysis<MachineLoopInfo>();
DT = &getAnalysis<MachineDominatorTree>();
+ AA = &getAnalysis<AliasAnalysis>();
for (MachineLoopInfo::iterator
I = LI->begin(), E = LI->end(); I != E; ++I) {
@@ -214,7 +218,7 @@
// Okay, this instruction does a load. As a refinement, we allow the target
// to decide whether the loaded value is actually a constant. If so, we can
// actually use it as a load.
- if (!TII->isInvariantLoad(&I))
+ if (!I.isInvariantLoad(AA))
// FIXME: we should be able to sink loads with no other side effects if
// there is nothing that can change memory from here until the end of
// block. This is a trivial form of alias analysis.
@@ -259,8 +263,6 @@
// Don't hoist an instruction that uses or defines a physical register.
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
- // If this is a physical register use, we can't move it. If it is a def,
- // we can move it, but only if the def is dead.
if (MO.isUse()) {
// 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,
diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp
index 636dad8..e5c3420 100644
--- a/lib/CodeGen/MachineSink.cpp
+++ b/lib/CodeGen/MachineSink.cpp
@@ -178,8 +178,6 @@
if (Reg == 0) continue;
if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
- // If this is a physical register use, we can't move it. If it is a def,
- // we can move it, but only if the def is dead.
if (MO.isUse()) {
// 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,
diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index b55e606..f50844f 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -375,7 +375,7 @@
// Treat all other stores conservatively.
goto new_chain;
} else if (TID.mayLoad()) {
- if (TII->isInvariantLoad(MI)) {
+ if (MI->isInvariantLoad()) {
// Invariant load, no chain dependencies needed!
} else if (const Value *V = getUnderlyingObjectForInstr(MI)) {
// A load from a specific PseudoSourceValue. Add precise dependencies.