Bug 614323 - ARM: prevent constant pool from being dumped in the middle of MICs r=dvander a=blocking-fennec

--HG--
extra : rebase_source : f4e2a61bf0c2bbd200733f78fef818f3c344dca3

js/src/assembler/assembler/ARMAssembler.h

@@ -922,6 +922,11 @@ namespace JSC {
             m_buffer.ensureSpace(insnSpace, constSpace);
         }
 
+        void ensureSpace(int space)
+        {
+            m_buffer.ensureSpace(space);
+        }
+
         int sizeOfConstantPool()
         {
             return m_buffer.sizeOfConstantPool();

js/src/assembler/assembler/MacroAssemblerARM.h

@@ -1056,6 +1056,11 @@ public:
         convertInt32ToDouble(ARMRegisters::S0, srcDest);
     }
 
+    void ensureSpace(int space)
+    {
+        m_assembler.ensureSpace(space);
+    }
+
     void forceFlushConstantPool()
     {
         m_assembler.forceFlushConstantPool();

js/src/methodjit/BaseCompiler.h

@@ -192,6 +192,50 @@ class Repatcher : public JSC::RepatchBuffer
     { }
 };
 
+/*
+ * On ARM, we periodically flush a constant pool into the instruction stream
+ * where constants are found using PC-relative addressing. This is necessary
+ * because the fixed-width instruction set doesn't support wide immediates.
+ *
+ * ICs perform repatching on the inline (fast) path by knowing small and
+ * generally fixed code location offset values where the patchable instructions
+ * live. Dumping a huge constant pool into the middle of an IC's inline path
+ * makes the distance between emitted instructions potentially variable and/or
+ * large, which makes the IC offsets invalid. We must reserve contiguous space
+ * up front to prevent this from happening.
+ */
+#ifdef JS_CPU_ARM
+class AutoReserveICSpace {
+    typedef Assembler::Label Label;
+    static const size_t reservedSpace = 64;
+
+    Assembler           &masm;
+#ifdef DEBUG
+    Label               startLabel;
+#endif
+
+  public:
+    AutoReserveICSpace(Assembler &masm) : masm(masm) {
+        masm.ensureSpace(reservedSpace);
+#ifdef DEBUG
+        startLabel = masm.label();
+#endif
+    }
+
+    ~AutoReserveICSpace() {
+#ifdef DEBUG
+        Label endLabel = masm.label();
+        int spaceUsed = masm.differenceBetween(startLabel, endLabel);
+        JS_ASSERT(spaceUsed >= 0);
+        JS_ASSERT(size_t(spaceUsed) <= reservedSpace);
+#endif
+    }
+};
+# define RESERVE_IC_SPACE(__masm) AutoReserveICSpace arics(__masm)
+#else
+# define RESERVE_IC_SPACE(__masm) /* Nothing. */
+#endif
+
 } /* namespace js */
 } /* namespace mjit */
 

js/src/methodjit/Compiler.cpp

@@ -4325,6 +4325,7 @@ mjit::Compiler::jsop_getgname(uint32 index)
     JS_ASSERT(fe->isTypeKnown() && fe->getKnownType() == JSVAL_TYPE_OBJECT);
 
     MICGenInfo mic(ic::MICInfo::GET);
+    RESERVE_IC_SPACE(masm);
     RegisterID objReg;
     Jump shapeGuard;
 
@@ -4427,6 +4428,7 @@ mjit::Compiler::jsop_setgname(uint32 index, bool usePropertyCache)
     JS_ASSERT_IF(objFe->isTypeKnown(), objFe->getKnownType() == JSVAL_TYPE_OBJECT);
 
     MICGenInfo mic(ic::MICInfo::SET);
+    RESERVE_IC_SPACE(masm);
     RegisterID objReg;
     Jump shapeGuard;