1344477 - Part 1: Add JSOP_CALL_IGNORES_RV for function call that ignores return value.

3 files changed, 32 insertions, 4 deletions

diff --git a/js/src/vm/Interpreter.cpp b/js/src/vm/Interpreter.cpp
index ad9e87a50..030f0f3b6 100644
--- a/js/src/vm/Interpreter.cpp
+++ b/js/src/vm/Interpreter.cpp
@@ -470,7 +470,13 @@ js::InternalCallOrConstruct(JSContext* cx, const CallArgs& args, MaybeConstruct
 
     if (fun->isNative()) {
         MOZ_ASSERT_IF(construct, !fun->isConstructor());
-        return CallJSNative(cx, fun->native(), args);
+        JSNative native = fun->native();
+        if (!construct && args.ignoresReturnValue()) {
+            const JSJitInfo* jitInfo = fun->jitInfo();
+            if (jitInfo && jitInfo->type() == JSJitInfo::IgnoresReturnValueNative)
+                native = jitInfo->ignoresReturnValueMethod;
+        }
+        return CallJSNative(cx, native, args);
     }
 
     if (!JSFunction::getOrCreateScript(cx, fun))
@@ -2975,6 +2981,7 @@ CASE(JSOP_FUNAPPLY)
 
 CASE(JSOP_NEW)
 CASE(JSOP_CALL)
+CASE(JSOP_CALL_IGNORES_RV)
 CASE(JSOP_CALLITER)
 CASE(JSOP_SUPERCALL)
 CASE(JSOP_FUNCALL)
@@ -2983,10 +2990,11 @@ CASE(JSOP_FUNCALL)
         cx->runtime()->spsProfiler.updatePC(script, REGS.pc);
 
     MaybeConstruct construct = MaybeConstruct(*REGS.pc == JSOP_NEW || *REGS.pc == JSOP_SUPERCALL);
+    bool ignoresReturnValue = *REGS.pc == JSOP_CALL_IGNORES_RV;
     unsigned argStackSlots = GET_ARGC(REGS.pc) + construct;
 
     MOZ_ASSERT(REGS.stackDepth() >= 2u + GET_ARGC(REGS.pc));
-    CallArgs args = CallArgsFromSp(argStackSlots, REGS.sp, construct);
+    CallArgs args = CallArgsFromSp(argStackSlots, REGS.sp, construct, ignoresReturnValue);
 
     JSFunction* maybeFun;
     bool isFunction = IsFunctionObject(args.calleev(), &maybeFun);
diff --git a/js/src/vm/Opcodes.h b/js/src/vm/Opcodes.h
index 095ef57ae..3c4d61a67 100644
--- a/js/src/vm/Opcodes.h
+++ b/js/src/vm/Opcodes.h
@@ -2282,14 +2282,23 @@
      *   Operands:
      *   Stack: =>
      */ \
-    macro(JSOP_JUMPTARGET,  230, "jumptarget",     NULL,  1,  0,  0,  JOF_BYTE)
+    macro(JSOP_JUMPTARGET,  230, "jumptarget",     NULL,  1,  0,  0,  JOF_BYTE)\
+    /*
+     * Like JSOP_CALL, but tells the function that the return value is ignored.
+     * stack.
+     *   Category: Statements
+     *   Type: Function
+     *   Operands: uint16_t argc
+     *   Stack: callee, this, args[0], ..., args[argc-1] => rval
+     *   nuses: (argc+2)
+     */ \
+    macro(JSOP_CALL_IGNORES_RV, 231, "call-ignores-rv", NULL, 3, -1, 1, JOF_UINT16|JOF_INVOKE|JOF_TYPESET)
 
 /*
  * In certain circumstances it may be useful to "pad out" the opcode space to
  * a power of two.  Use this macro to do so.
  */
 #define FOR_EACH_TRAILING_UNUSED_OPCODE(macro) \
-    macro(231) \
     macro(232) \
     macro(233) \
     macro(234) \
diff --git a/js/src/vm/Stack.h b/js/src/vm/Stack.h
index dc9306c99..23e621344 100644
--- a/js/src/vm/Stack.h
+++ b/js/src/vm/Stack.h
@@ -1006,6 +1006,17 @@ class InvokeArgs : public detail::GenericArgsBase<NO_CONSTRUCT>
     explicit InvokeArgs(JSContext* cx) : Base(cx) {}
 };
 
+/** Function call args of statically-unknown count. */
+class InvokeArgsMaybeIgnoresReturnValue : public detail::GenericArgsBase<NO_CONSTRUCT>
+{
+    using Base = detail::GenericArgsBase<NO_CONSTRUCT>;
+
+  public:
+    explicit InvokeArgsMaybeIgnoresReturnValue(JSContext* cx, bool ignoresReturnValue) : Base(cx) {
+        this->ignoresReturnValue_ = ignoresReturnValue;
+    }
+};
+
 /** Function call args of statically-known count. */
 template <size_t N>
 class FixedInvokeArgs : public detail::FixedArgsBase<NO_CONSTRUCT, N>