change machinelicm to use MachineInstr::isSafeToMove. No
intended functionality change.
The avoidance of hoistiing implicitdef seems wrong though.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@108109 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 709b2d1..956d21c 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -127,8 +127,8 @@
void AddToLiveIns(unsigned Reg);
/// IsLICMCandidate - Returns true if the instruction may be a suitable
- /// candidate for LICM. e.g. If the instruction is a call, then it's obviously
- /// not safe to hoist it.
+ /// candidate for LICM. e.g. If the instruction is a call, then it's
+ /// obviously not safe to hoist it.
bool IsLICMCandidate(MachineInstr &I);
/// IsLoopInvariantInst - Returns true if the instruction is loop
@@ -497,26 +497,16 @@
/// candidate for LICM. e.g. If the instruction is a call, then it's obviously
/// not safe to hoist it.
bool MachineLICM::IsLICMCandidate(MachineInstr &I) {
+ // It is not profitable to hoist implicitdefs. FIXME: Why not? what if they
+ // are an argument to some other otherwise-hoistable instruction?
if (I.isImplicitDef())
return false;
-
- const TargetInstrDesc &TID = I.getDesc();
- // Ignore stuff that we obviously can't hoist.
- if (TID.mayStore() || TID.isCall() || TID.isTerminator() ||
- TID.hasUnmodeledSideEffects())
+ // Check if it's safe to move the instruction.
+ bool DontMoveAcrossStore = true;
+ if (!I.isSafeToMove(TII, AA, DontMoveAcrossStore))
return false;
-
- if (TID.mayLoad()) {
- // 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 (!I.isInvariantLoad(AA))
- // FIXME: we should be able to hoist loads with no other side effects if
- // there are no other instructions which can change memory in this loop.
- // This is a trivial form of alias analysis.
- return false;
- }
+
return true;
}