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;
}