Bug 915301: Check Float32 coherency; r=sstangl

js/src/jit-test/tests/ion/bug915301.js

@@ -0,0 +1,23 @@
+setJitCompilerOption("ion.usecount.trigger", 50);
+var f32 = new Float32Array(32);
+f32[0] = 0;
+
+function g(x) {
+    eval(""); // don't inline
+    return x + 4;
+}
+
+function f(n) {
+    var x;
+    if (n > 10000) {
+        x = 4.5;
+    } else {
+        x = f32[0];
+    }
+    f32[0] = g(x);
+}
+
+for (var n = 0; n < 100; n++)
+    f(n);
+
+assertEq(f32[0], 400);

js/src/jit/IonAnalysis.cpp

@@ -400,6 +400,7 @@ class TypeAnalyzer
     bool adjustInputs(MDefinition *def);
     bool insertConversions();
 
+    bool checkFloatCoherency();
     bool graphContainsFloat32();
     bool markPhiConsumers();
     bool markPhiProducers();
@@ -900,6 +901,42 @@ TypeAnalyzer::tryEmitFloatOperations()
     return true;
 }
 
+bool
+TypeAnalyzer::checkFloatCoherency()
+{
+#ifdef DEBUG
+    // Asserts that all Float32 instructions are flowing into Float32 consumers or specialized
+    // operations
+    for (ReversePostorderIterator block(graph.rpoBegin()); block != graph.rpoEnd(); ++block) {
+        if (mir->shouldCancel("Check Float32 coherency"))
+            return false;
+
+        for (MDefinitionIterator def(*block); def; def++) {
+            if (def->type() != MIRType_Float32)
+                continue;
+            if (def->isPassArg()) // no check for PassArg as it is broken, see bug 915479
+                continue;
+
+            for (MUseDefIterator use(*def); use; use++) {
+                MDefinition *consumer = use.def();
+                // The only valid uses of a Float32 are:
+                // - an operation that can consume Float32
+                // - an operation that has been specialized to Float32 (for instance, an add)
+                // - a conversion to Double
+                if (consumer->canConsumeFloat32())
+                    continue;
+                if (consumer->type() == MIRType_Float32)
+                    continue;
+                if (consumer->isToDouble())
+                    continue;
+                MOZ_ASSUME_UNREACHABLE("Float32 flowing into a non float specialized operation");
+            }
+        }
+    }
+#endif
+    return true;
+}
+
 bool
 TypeAnalyzer::analyze()
 {
@@ -909,6 +946,8 @@ TypeAnalyzer::analyze()
         return false;
     if (!insertConversions())
         return false;
+    if (!checkFloatCoherency())
+        return false;
     return true;
 }