Bug 1084612 - IonMonkey: Reduce the complexity of the assertion of th…

…e graph coherency. r=sunfish

js/src/jit/IonAnalysis.cpp

@@ -1776,28 +1776,73 @@ CheckPredecessorImpliesSuccessor(MBasicBlock *A, MBasicBlock *B)
     return false;
 }
 
-static bool
-CheckOperandImpliesUse(MNode *n, MDefinition *operand)
-{
-    MOZ_ASSERT(!operand->isDiscarded());
-    MOZ_ASSERT(operand->block() != nullptr);
+// If you have issues with the usesBalance assertions, then define the macro
+// _DEBUG_CHECK_OPERANDS_USES_BALANCE to spew information on the error output.
+// This output can then be processed with the following awk script to filter and
+// highlight which checks are missing or if there is an unexpected operand /
+// use.
+//
+// define _DEBUG_CHECK_OPERANDS_USES_BALANCE 1
+/*
 
-    for (MUseIterator i = operand->usesBegin(); i != operand->usesEnd(); i++) {
-        if (i->consumer() == n)
-            return true;
+$ ./js 2>stderr.log
+$ gawk '
+    /^==Check/ { context = ""; state = $2; }
+    /^[a-z]/ { context = context "\n\t" $0; }
+    /^==End/ {
+      if (state == "Operand") {
+        list[context] = list[context] - 1;
+      } else if (state == "Use") {
+        list[context] = list[context] + 1;
+      }
     }
-    return false;
+    END {
+      for (ctx in list) {
+        if (list[ctx] > 0) {
+          print "Missing operand check", ctx, "\n"
+        }
+        if (list[ctx] < 0) {
+          print "Missing use check", ctx, "\n"
+        }
+      };
+    }'  < stderr.log
+
+*/
+
+static void
+CheckOperand(const MNode *consumer, const MUse *use, int32_t *usesBalance)
+{
+    MOZ_ASSERT(use->hasProducer());
+    MDefinition *producer = use->producer();
+    MOZ_ASSERT(!producer->isDiscarded());
+    MOZ_ASSERT(producer->block() != nullptr);
+    MOZ_ASSERT(use->consumer() == consumer);
+#ifdef _DEBUG_CHECK_OPERANDS_USES_BALANCE
+    fprintf(stderr, "==Check Operand\n");
+    use->producer()->dump(stderr);
+    fprintf(stderr, "  index: %zu\n", use->consumer()->indexOf(use));
+    use->consumer()->dump(stderr);
+    fprintf(stderr, "==End\n");
+#endif
+    --*usesBalance;
 }
 
-static bool
-CheckUseImpliesOperand(MDefinition *def, MUse *use)
+static void
+CheckUse(const MDefinition *producer, const MUse *use, int32_t *usesBalance)
 {
     MOZ_ASSERT(!use->consumer()->block()->isDead());
     MOZ_ASSERT_IF(use->consumer()->isDefinition(),
                   !use->consumer()->toDefinition()->isDiscarded());
     MOZ_ASSERT(use->consumer()->block() != nullptr);
-
-    return use->consumer()->getOperand(use->index()) == def;
+    MOZ_ASSERT(use->consumer()->getOperand(use->index()) == producer);
+#ifdef _DEBUG_CHECK_OPERANDS_USES_BALANCE
+    fprintf(stderr, "==Check Use\n");
+    use->producer()->dump(stderr);
+    fprintf(stderr, "  index: %zu\n", use->consumer()->indexOf(use));
+    use->consumer()->dump(stderr);
+    fprintf(stderr, "==End\n");
+#endif
+    ++*usesBalance;
 }
 #endif // DEBUG
 
@@ -1821,6 +1866,7 @@ jit::AssertBasicGraphCoherency(MIRGraph &graph)
 
     // Assert successor and predecessor list coherency.
     uint32_t count = 0;
+    int32_t usesBalance = 0;
     for (MBasicBlockIterator block(graph.begin()); block != graph.end(); block++) {
         count++;
 
@@ -1848,10 +1894,8 @@ jit::AssertBasicGraphCoherency(MIRGraph &graph)
             // the entry resume point because we are still storing resume points
             // in the InlinePropertyTable.
             MOZ_ASSERT_IF(iter->instruction(), iter->instruction()->block() == *block);
-            for (uint32_t i = 0, e = iter->numOperands(); i < e; i++) {
-                MOZ_ASSERT(iter->getUseFor(i)->hasProducer());
-                MOZ_ASSERT(CheckOperandImpliesUse(*iter, iter->getOperand(i)));
-            }
+            for (uint32_t i = 0, e = iter->numOperands(); i < e; i++)
+                CheckOperand(*iter, iter->getUseFor(i), &usesBalance);
         }
         for (MPhiIterator phi(block->phisBegin()); phi != block->phisEnd(); phi++) {
             MOZ_ASSERT(phi->numOperands() == block->numPredecessors());
@@ -1872,9 +1916,9 @@ jit::AssertBasicGraphCoherency(MIRGraph &graph)
 
             // Assert that use chains are valid for this instruction.
             for (uint32_t i = 0, end = iter->numOperands(); i < end; i++)
-                MOZ_ASSERT(CheckOperandImpliesUse(*iter, iter->getOperand(i)));
+                CheckOperand(*iter, iter->getUseFor(i), &usesBalance);
             for (MUseIterator use(iter->usesBegin()); use != iter->usesEnd(); use++)
-                MOZ_ASSERT(CheckUseImpliesOperand(*iter, *use));
+                CheckUse(*iter, *use, &usesBalance);
 
             if (iter->isInstruction()) {
                 if (MResumePoint *resume = iter->toInstruction()->resumePoint()) {
@@ -1888,17 +1932,21 @@ jit::AssertBasicGraphCoherency(MIRGraph &graph)
                 MOZ_ASSERT(!iter->hasLiveDefUses());
         }
 
+        // The control instruction is not visited by the MDefinitionIterator.
         MControlInstruction *control = block->lastIns();
         MOZ_ASSERT(control->block() == *block);
         MOZ_ASSERT(!control->hasUses());
         MOZ_ASSERT(control->type() == MIRType_None);
         MOZ_ASSERT(!control->isDiscarded());
         MOZ_ASSERT(!control->isRecoveredOnBailout());
         MOZ_ASSERT(control->resumePoint() == nullptr);
-        for (uint32_t i = 0, end = control->numOperands(); i < end; ++i)
-            MOZ_ASSERT(CheckOperandImpliesUse(control, control->getOperand(i)));
+        for (uint32_t i = 0, end = control->numOperands(); i < end; i++)
+            CheckOperand(control, control->getUseFor(i), &usesBalance);
     }
 
+    // In case issues, see the _DEBUG_CHECK_OPERANDS_USES_BALANCE macro above.
+    MOZ_ASSERT(usesBalance <= 0, "More use checks than operand checks");
+    MOZ_ASSERT(usesBalance >= 0, "More operand checks than use checks");
     MOZ_ASSERT(graph.numBlocks() == count);
 #endif
 }

js/src/jit/MIR.h

@@ -255,6 +255,9 @@ class MNode : public TempObject
     virtual void dump() const = 0;
 
   protected:
+    // Need visibility on getUseFor to avoid O(n^2) complexity.
+    friend void AssertBasicGraphCoherency(MIRGraph &graph);
+
     // Gets the MUse corresponding to given operand.
     virtual MUse *getUseFor(size_t index) = 0;
     virtual const MUse *getUseFor(size_t index) const = 0;