Add a method to MachineInstr for testing whether it makes
any volatile memory references.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56528 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineInstr.cpp b/lib/CodeGen/MachineInstr.cpp
index a365f20..7d44d4e 100644
--- a/lib/CodeGen/MachineInstr.cpp
+++ b/lib/CodeGen/MachineInstr.cpp
@@ -711,16 +711,11 @@
// 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() && !TII->isInvariantLoad(this))
// Otherwise, this is a real load. If there is a store between the load and
- // end of block, we can't sink the load.
- //
- // FIXME: we can't do this transformation until we know that the load is
- // not volatile, and machineinstrs don't keep this info. :(
- //
- //if (SawStore)
- return false;
- }
+ // end of block, or if the laod is volatile, we can't move it.
+ return SawStore || hasVolatileMemoryRef();
+
return true;
}
@@ -749,6 +744,32 @@
return true;
}
+/// hasVolatileMemoryRef - Return true if this instruction may have a
+/// volatile memory reference, or if the information describing the
+/// memory reference is not available. Return false if it is known to
+/// have no volatile memory references.
+bool MachineInstr::hasVolatileMemoryRef() const {
+ // An instruction known never to access memory won't have a volatile access.
+ if (!TID->mayStore() &&
+ !TID->mayLoad() &&
+ !TID->isCall() &&
+ !TID->hasUnmodeledSideEffects())
+ return false;
+
+ // Otherwise, if the instruction has no memory reference information,
+ // conservatively assume it wasn't preserved.
+ if (memoperands_empty())
+ return true;
+
+ // Check the memory reference information for volatile references.
+ for (std::list<MachineMemOperand>::const_iterator I = memoperands_begin(),
+ E = memoperands_end(); I != E; ++I)
+ if (I->isVolatile())
+ return true;
+
+ return false;
+}
+
void MachineInstr::dump() const {
cerr << " " << *this;
}