--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/graal/Compiler/src/com/sun/c1x/opt/CEEliminator.java	Wed Apr 27 11:43:22 2011 +0200
@@ -0,0 +1,232 @@
+/*
+ * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package com.sun.c1x.opt;
+
+import com.sun.c1x.*;
+import com.sun.c1x.graph.*;
+import com.sun.c1x.ir.*;
+import com.sun.c1x.value.*;
+import com.sun.c1x.value.FrameState.*;
+import com.sun.cri.ci.*;
+
+/**
+ * This class implements conditional-expression elimination, which replaces some
+ * simple branching constructs with conditional moves.
+ *
+ * @author Ben L. Titzer
+ */
+public class CEEliminator implements BlockClosure {
+
+    final IR ir;
+    final InstructionSubstituter subst;
+
+    public CEEliminator(IR ir) {
+        this.ir = ir;
+        this.subst = new InstructionSubstituter(ir);
+        ir.startBlock.iteratePreOrder(this);
+        subst.finish();
+    }
+
+    void adjustExceptionEdges(BlockBegin block, BlockBegin sux) {
+        int e = sux.numberOfExceptionHandlers();
+        for (int i = 0; i < e; i++) {
+            BlockBegin xhandler = sux.exceptionHandlerAt(i);
+            block.addExceptionHandler(xhandler);
+
+            assert xhandler.isPredecessor(sux) : "missing predecessor";
+            if (sux.numberOfPreds() == 0) {
+                // sux is disconnected from graph so disconnect from exception handlers
+                xhandler.removePredecessor(sux);
+            }
+            if (!xhandler.isPredecessor(block)) {
+                xhandler.addPredecessor(block);
+            }
+        }
+    }
+
+    public void apply(BlockBegin block) {
+        // 1) check that block ends with an If
+        if (!(block.end() instanceof If)) {
+            return;
+        }
+        If curIf = (If) block.end();
+
+        // check that the if's operands are of int or object type
+        CiKind ifType = curIf.x().kind;
+        if (!ifType.isInt() && !ifType.isObject()) {
+            return;
+        }
+
+        BlockBegin tBlock = curIf.trueSuccessor();
+        BlockBegin fBlock = curIf.falseSuccessor();
+        Instruction tCur = tBlock.next();
+        Instruction fCur = fBlock.next();
+
+        // one Constant may be present between BlockBegin and BlockEnd
+        Instruction tConst = null;
+        Instruction fConst = null;
+        if (tCur instanceof Constant) {
+            tConst = tCur;
+            tCur = tCur.next();
+        }
+        if (fCur instanceof Constant) {
+            fConst = fCur;
+            fCur = fCur.next();
+        }
+
+        // check that both branches end with a goto
+        if (!(tCur instanceof Goto) || !(fCur instanceof Goto)) {
+            return;
+        }
+        Goto tGoto = (Goto) tCur;
+        Goto fGoto = (Goto) fCur;
+
+        // check that both gotos merge into the same block
+        BlockBegin sux = tGoto.defaultSuccessor();
+        if (sux != fGoto.defaultSuccessor()) {
+            return;
+        }
+
+        // check that at least one word was pushed on suxState
+        FrameState suxState = sux.stateBefore();
+        if (suxState.stackSize() <= curIf.stateAfter().stackSize()) {
+            return;
+        }
+
+        // check that phi function is present at end of successor stack and that
+        // only this phi was pushed on the stack
+        final Value suxPhi = suxState.stackAt(curIf.stateAfter().stackSize());
+        if (suxPhi == null || !(suxPhi instanceof Phi) || ((Phi) suxPhi).block() != sux) {
+            return;
+        }
+        if (suxPhi.kind.sizeInSlots() != suxState.stackSize() - curIf.stateAfter().stackSize()) {
+            return;
+        }
+
+        // get the values that were pushed in the true- and false-branch
+        Value tValue = tGoto.stateAfter().stackAt(curIf.stateAfter().stackSize());
+        Value fValue = fGoto.stateAfter().stackAt(curIf.stateAfter().stackSize());
+
+        assert tValue.kind == fValue.kind : "incompatible types";
+
+        if (tValue.kind.isFloat() || tValue.kind.isDouble()) {
+            // backend does not support conditional moves on floats
+            return;
+        }
+
+        // check that successor has no other phi functions but suxPhi
+        // this can happen when tBlock or fBlock contained additional stores to local variables
+        // that are no longer represented by explicit instructions
+        boolean suxHasOtherPhi = sux.stateBefore().forEachPhi(sux, new PhiProcedure() {
+            public boolean doPhi(Phi phi) {
+                return phi == suxPhi;
+            }
+        });
+        if (suxHasOtherPhi) {
+            return;
+        }
+
+        // check that true and false blocks don't have phis
+        if (tBlock.stateBefore().hasPhis() || fBlock.stateBefore().hasPhis()) {
+            return;
+        }
+
+        // 2) cut off the original if and replace with constants and a Goto
+        // cut curIf away and get node before
+        Instruction ifPrev = curIf.prev(block);
+        int bci = curIf.bci();
+
+        // append constants of true- and false-block if necessary
+        // clone constants because original block must not be destroyed
+        assert (tValue != fConst && fValue != tConst) || tConst == fConst : "mismatch";
+        if (tValue == tConst) {
+            Constant tc = new Constant(tConst.asConstant());
+            tValue = tc;
+            ifPrev = ifPrev.setNext(tc, bci);
+        }
+        if (fValue == fConst) {
+            Constant fc = new Constant(fConst.asConstant());
+            fValue = fc;
+            ifPrev = ifPrev.setNext(fc, bci);
+        }
+
+        Value result;
+        if (tValue == fValue) {
+            // conditional chooses the same value regardless
+            result = tValue;
+            C1XMetrics.RedundantConditionals++;
+        } else {
+            // it is very unlikely that the condition can be statically decided
+            // (this was checked previously by the Canonicalizer), so always
+            // append IfOp
+            result = new IfOp(curIf.x(), curIf.condition(), curIf.y(), tValue, fValue);
+            ifPrev = ifPrev.setNext((Instruction) result, bci);
+        }
+
+        // append Goto to successor
+        FrameState stateBefore = curIf.isSafepoint() ? curIf.stateAfter() : null;
+        Goto newGoto = new Goto(sux, stateBefore, curIf.isSafepoint() || tGoto.isSafepoint() || fGoto.isSafepoint());
+
+        // prepare state for Goto
+        FrameState tempGotoState = curIf.stateAfter();
+        while (suxState.scope() != tempGotoState.scope()) {
+            tempGotoState = tempGotoState.popScope();
+            assert tempGotoState != null : "states do not match up";
+        }
+        MutableFrameState gotoState = tempGotoState.copy();
+        gotoState.push(result.kind, result);
+        assert gotoState.isSameAcrossScopes(suxState) : "states must match now";
+        // ATTN: assumption: last use of gotoState, else add .immutableCopy()
+        newGoto.setStateAfter(gotoState);
+
+        // Steal the bci for the goto from the sux
+        ifPrev = ifPrev.setNext(newGoto, sux.bci());
+
+        // update block end (will remove this block from tBlock and fBlock predecessors)
+        block.setEnd(newGoto);
+
+        // remove blocks if they became unreachable
+        tryRemove(tBlock);
+        tryRemove(fBlock);
+
+        // substitute the phi if possible
+        Phi suxAsPhi = (Phi) suxPhi;
+        if (suxAsPhi.inputCount() == 1) {
+            // if the successor block now has only one predecessor
+            assert suxAsPhi.inputAt(0) == result : "screwed up phi";
+            subst.setSubst(suxPhi, result);
+
+            // 3) successfully eliminated a conditional expression
+            C1XMetrics.ConditionalEliminations++;
+        }
+    }
+
+    private void tryRemove(BlockBegin succ) {
+        if (succ.numberOfPreds() == 0) {
+            // block just became unreachable
+            for (BlockBegin s : succ.end().successors()) {
+                s.predecessors().remove(succ);
+            }
+        }
+    }
+}