From 8d17160e2cf9a1645b4b06b0cd575aef6195b108 Mon Sep 17 00:00:00 2001 From: Jakob Stoklund Olesen Date: Tue, 13 Apr 2010 19:06:14 +0000 Subject: Teach MachineSinking to handle easy critical edges. Sometimes it is desirable to sink instructions along a critical edge: x = ... if (a && b) ... else use(x); The 'a && b' condition creates a critical edge to the else block, but we still want to sink the computation of x into the block. The else block is dominated by the parent block, so we are not pushing instructions into new code paths. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101165 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/MachineSink.cpp | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) (limited to 'lib/CodeGen/MachineSink.cpp') diff --git a/lib/CodeGen/MachineSink.cpp b/lib/CodeGen/MachineSink.cpp index e659619015..5cf17298ca 100644 --- a/lib/CodeGen/MachineSink.cpp +++ b/lib/CodeGen/MachineSink.cpp @@ -276,8 +276,23 @@ bool MachineSinking::SinkInstruction(MachineInstr *MI, bool &SawStore) { // but for now we just punt. // FIXME: Split critical edges if not backedges. if (SuccToSinkTo->pred_size() > 1) { - DEBUG(dbgs() << " *** PUNTING: Critical edge found\n"); - return false; + // We cannot sink a load across a critical edge - there may be stores in + // other code paths. + bool store = true; + if (!MI->isSafeToMove(TII, AA, store)) { + DEBUG(dbgs() << " *** PUNTING: Wont sink load along critical edge.\n"); + return false; + } + + // We don't want to sink across a critical edge if we don't dominate the + // successor. We could be introducing calculations to new code paths. + if (!DT->dominates(ParentBlock, SuccToSinkTo)) { + DEBUG(dbgs() << " *** PUNTING: Critical edge found\n"); + return false; + } + + // Otherwise we are OK with sinking along a critical edge. + DEBUG(dbgs() << "Sinking along critical edge.\n"); } // Determine where to insert into. Skip phi nodes. -- cgit v1.2.3-18-g5258