diff options
Diffstat (limited to 'chapter19/src/main/java')
3 files changed, 46 insertions, 0 deletions
diff --git a/chapter19/src/main/java/com/seaofnodes/simple/node/LoadNode.java b/chapter19/src/main/java/com/seaofnodes/simple/node/LoadNode.java index 1991c62c..a06d1291 100644 --- a/chapter19/src/main/java/com/seaofnodes/simple/node/LoadNode.java +++ b/chapter19/src/main/java/com/seaofnodes/simple/node/LoadNode.java @@ -51,6 +51,7 @@ public class LoadNode extends MemOpNode { @Override public Type compute() { + if( ptr()._type==Type.TOP ) return Type.TOP; // Dead pointer, not a type error. Type t = MemMergeNode.contents(mem(),_alias,this); // Update declared forward ref to the actual. if( _declaredType.isFRef() && t instanceof TypeMemPtr tmp && !tmp.isFRef() ) diff --git a/chapter19/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java b/chapter19/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java index 411370e1..38cbcd5b 100644 --- a/chapter19/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java +++ b/chapter19/src/main/java/com/seaofnodes/simple/node/MemPhiNode.java @@ -36,6 +36,11 @@ public class MemPhiNode extends PhiNode { setDef(i,CodeGen.CODE.add(mem.alias(_alias))); return this; } + if( nIns()==3 && region() instanceof LoopNode loop && !loop.inProgress() && + in(2) instanceof StoreNode st && st.mem()==this ) { + Node sink = st.sink(this); + if( sink!=null ) return sink; + } return super.idealize(); } diff --git a/chapter19/src/main/java/com/seaofnodes/simple/node/StoreNode.java b/chapter19/src/main/java/com/seaofnodes/simple/node/StoreNode.java index 0d39980a..86c759bd 100644 --- a/chapter19/src/main/java/com/seaofnodes/simple/node/StoreNode.java +++ b/chapter19/src/main/java/com/seaofnodes/simple/node/StoreNode.java @@ -88,6 +88,46 @@ public class StoreNode extends MemOpNode { return null; } + // Phi(mem, Store(phi,ptr,off,val)) -> Store(mem,ptr,off,Phi(load(mem),val)). + // With no observers of the backedge store, only the last value matters. + // The entry load preserves the field even when the loop takes zero trips. + Node sink(MemPhiNode phi) { + addDepForwards(phi); + if( nOuts()!=1 ) return null; + ptr().addDep(phi); + // Start with a fixed field of an allocation dominating the loop. + // In particular, do not sink stores through a loop-varying address. + if( !(ptr() instanceof ProjNode p) || !(p.in(0) instanceof NewNode obj) || + !(ptr()._type instanceof TypeMemPtr tmp) || tmp._obj.isAry() || + !(off() instanceof ConstantNode) || err()!=null ) return null; + LoopNode loop = (LoopNode)phi.region(); + // Bulk splitting identifies precise slices by Region/alias. Finish it + // before replacing this memory point with a Store. + for( Node use : loop._outputs ) + if( use instanceof BulkMemPhiNode ) { + use.addDepForwards(phi); + return null; + } + obj.addDep(phi); + CFGNode ctrl = loop.entry(); + while( ctrl!=null && ctrl!=obj.cfg0() ) { + ctrl.addDep(phi); + ctrl=ctrl.idom(phi); + } + if( ctrl==null ) return null; + + Node mem = phi.in(1); + Node init = new LoadNode(_loc,_name,_alias,_declaredType,mem,ptr(),off()).peephole(); + Node value = new PhiNode(_name,_declaredType,loop,init,val()).peephole(); + Node sink = new StoreNode(_loc,_name,_alias,_declaredType,mem,ptr(),off(),value,_init); + // Break the memory cycle, killing the old store. Keep the Phi alive + // even if that store was its last use, until our caller replaces it. + phi.keep(); + phi.setDef(2,mem); + phi.unkeep(); + return sink; + } + // Check that "mem" has no uses except "this" private boolean checkOnlyUse(Node mem) { if( mem.nOuts()==1 ) return true; |