From 9b61f33351a92f6a87065adae713c02497780887 Mon Sep 17 00:00:00 2001 From: Evan Cheng Date: Wed, 4 Feb 2009 07:17:49 +0000 Subject: [PATCH] For now, only hoist re-materilizable instructions. LICM will increase register pressure. We want to avoid spilling more instructions if it's possible. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@63725 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/MachineLICM.cpp | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp index fbf21139ac4..4e2d9eeb18d 100644 --- a/lib/CodeGen/MachineLICM.cpp +++ b/lib/CodeGen/MachineLICM.cpp @@ -186,18 +186,27 @@ bool MachineLICM::IsLoopInvariantInst(MachineInstr &I) { if (TID.mayStore() || TID.isCall() || TID.isTerminator() || TID.hasUnmodeledSideEffects()) return false; - + + bool isInvLoad = 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 (!TII->isInvariantLoad(&I)) + isInvLoad = TII->isInvariantLoad(&I); + if (!isInvLoad) // 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. return false; } + // FIXME: For now, only hoist re-materilizable instructions. LICM will + // increase register pressure. We want to make sure it doesn't increase + // spilling. + if (!isInvLoad && (!TID.isRematerializable() || + !TII->isTriviallyReMaterializable(&I))) + return false; + DEBUG({ DOUT << "--- Checking if we can hoist " << I; if (I.getDesc().getImplicitUses()) {