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

2 files changed, 53 insertions, 30 deletions

diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index 7582e8df18..c2eae43444 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -4603,7 +4603,7 @@ BytecodeEmitter::emitSwitch(ParseNode* pn)
             // If the expression is a literal, suppress line number emission so
             // that debugging works more naturally.
             if (caseValue) {
-                if (!emitTree(caseValue,
+                if (!emitTree(caseValue, ValueUsage::WantValue,
                               caseValue->isLiteral() ? SUPPRESS_LINENOTE : EMIT_LINENOTE))
                 {
                     return false;
@@ -6652,7 +6652,7 @@ BytecodeEmitter::emitLexicalScopeBody(ParseNode* body, EmitLineNumberNote emitLi
     }
 
     // Line notes were updated by emitLexicalScope.
-    return emitTree(body, emitLineNote);
+    return emitTree(body, ValueUsage::WantValue, emitLineNote);
 }
 
 // Using MOZ_NEVER_INLINE in here is a workaround for llvm.org/pr14047. See
@@ -6754,9 +6754,9 @@ BytecodeEmitter::emitRequireObjectCoercible()
         return false;
     if (!emit2(JSOP_PICK, 2))              // VAL REQUIREOBJECTCOERCIBLE UNDEFINED VAL
         return false;
-    if (!emitCall(JSOP_CALL, 1))           // VAL IGNORED
+    if (!emitCall(JSOP_CALL_IGNORES_RV, 1))// VAL IGNORED
         return false;
-    checkTypeSet(JSOP_CALL);
+    checkTypeSet(JSOP_CALL_IGNORES_RV);
 
     if (!emit1(JSOP_POP))                  // VAL
         return false;
@@ -7276,12 +7276,14 @@ BytecodeEmitter::emitCStyleFor(ParseNode* pn, EmitterScope* headLexicalEmitterSc
         // scope, but we still need to emit code for the initializers.)
         if (!updateSourceCoordNotes(init->pn_pos.begin))
             return false;
-        if (!emitTree(init))
-            return false;
-
-        if (!init->isForLoopDeclaration()) {
+        if (init->isForLoopDeclaration()) {
+            if (!emitTree(init))
+                return false;
+        } else {
             // 'init' is an expression, not a declaration. emitTree left its
             // value on the stack.
+            if (!emitTree(init, ValueUsage::IgnoreValue))
+                return false;
             if (!emit1(JSOP_POP))
                 return false;
         }
@@ -7363,7 +7365,7 @@ BytecodeEmitter::emitCStyleFor(ParseNode* pn, EmitterScope* headLexicalEmitterSc
 
         if (!updateSourceCoordNotes(update->pn_pos.begin))
             return false;
-        if (!emitTree(update))
+        if (!emitTree(update, ValueUsage::IgnoreValue))
             return false;
         if (!emit1(JSOP_POP))
             return false;
@@ -8690,8 +8692,9 @@ BytecodeEmitter::emitStatement(ParseNode* pn)
 
     if (useful) {
         JSOp op = wantval ? JSOP_SETRVAL : JSOP_POP;
+        ValueUsage valueUsage = wantval ? ValueUsage::WantValue : ValueUsage::IgnoreValue;
         MOZ_ASSERT_IF(pn2->isKind(PNK_ASSIGN), pn2->isOp(JSOP_NOP));
-        if (!emitTree(pn2))
+        if (!emitTree(pn2, valueUsage))
             return false;
         if (!emit1(op))
             return false;
@@ -9041,7 +9044,7 @@ BytecodeEmitter::emitOptimizeSpread(ParseNode* arg0, JumpList* jmp, bool* emitte
 }
 
 bool
-BytecodeEmitter::emitCallOrNew(ParseNode* pn)
+BytecodeEmitter::emitCallOrNew(ParseNode* pn, ValueUsage valueUsage /* = ValueUsage::WantValue */)
 {
     bool callop = pn->isKind(PNK_CALL) || pn->isKind(PNK_TAGGED_TEMPLATE);
     /*
@@ -9220,13 +9223,20 @@ BytecodeEmitter::emitCallOrNew(ParseNode* pn)
     }
 
     if (!spread) {
-        if (!emitCall(pn->getOp(), argc, pn))
-            return false;
+        if (pn->getOp() == JSOP_CALL && valueUsage == ValueUsage::IgnoreValue) {
+            if (!emitCall(JSOP_CALL_IGNORES_RV, argc, pn))
+                return false;
+            checkTypeSet(JSOP_CALL_IGNORES_RV);
+        } else {
+            if (!emitCall(pn->getOp(), argc, pn))
+                return false;
+            checkTypeSet(pn->getOp());
+        }
     } else {
         if (!emit1(pn->getOp()))
             return false;
+        checkTypeSet(pn->getOp());
     }
-    checkTypeSet(pn->getOp());
     if (pn->isOp(JSOP_EVAL) ||
         pn->isOp(JSOP_STRICTEVAL) ||
         pn->isOp(JSOP_SPREADEVAL) ||
@@ -9324,12 +9334,13 @@ BytecodeEmitter::emitLogical(ParseNode* pn)
 }
 
 bool
-BytecodeEmitter::emitSequenceExpr(ParseNode* pn)
+BytecodeEmitter::emitSequenceExpr(ParseNode* pn,
+                                  ValueUsage valueUsage /* = ValueUsage::WantValue */)
 {
     for (ParseNode* child = pn->pn_head; ; child = child->pn_next) {
         if (!updateSourceCoordNotes(child->pn_pos.begin))
             return false;
-        if (!emitTree(child))
+        if (!emitTree(child, child->pn_next ? ValueUsage::IgnoreValue : valueUsage))
             return false;
         if (!child->pn_next)
             break;
@@ -9392,7 +9403,8 @@ BytecodeEmitter::emitLabeledStatement(const LabeledStatement* pn)
 }
 
 bool
-BytecodeEmitter::emitConditionalExpression(ConditionalExpression& conditional)
+BytecodeEmitter::emitConditionalExpression(ConditionalExpression& conditional,
+                                           ValueUsage valueUsage /* = ValueUsage::WantValue */)
 {
     /* Emit the condition, then branch if false to the else part. */
     if (!emitTree(&conditional.condition()))
@@ -9402,13 +9414,13 @@ BytecodeEmitter::emitConditionalExpression(ConditionalExpression& conditional)
     if (!ifThenElse.emitCond())
         return false;
 
-    if (!emitTreeInBranch(&conditional.thenExpression()))
+    if (!emitTreeInBranch(&conditional.thenExpression(), valueUsage))
         return false;
 
     if (!ifThenElse.emitElse())
         return false;
 
-    if (!emitTreeInBranch(&conditional.elseExpression()))
+    if (!emitTreeInBranch(&conditional.elseExpression(), valueUsage))
         return false;
 
     if (!ifThenElse.emitEnd())
@@ -10288,7 +10300,8 @@ BytecodeEmitter::emitClass(ParseNode* pn)
 }
 
 bool
-BytecodeEmitter::emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote)
+BytecodeEmitter::emitTree(ParseNode* pn, ValueUsage valueUsage /* = ValueUsage::WantValue */,
+                          EmitLineNumberNote emitLineNote /* = EMIT_LINENOTE */)
 {
     JS_CHECK_RECURSION(cx, return false);
 
@@ -10410,7 +10423,7 @@ BytecodeEmitter::emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote)
         break;
 
       case PNK_COMMA:
-        if (!emitSequenceExpr(pn))
+        if (!emitSequenceExpr(pn, valueUsage))
             return false;
         break;
 
@@ -10432,7 +10445,7 @@ BytecodeEmitter::emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote)
         break;
 
       case PNK_CONDITIONAL:
-        if (!emitConditionalExpression(pn->as<ConditionalExpression>()))
+        if (!emitConditionalExpression(pn->as<ConditionalExpression>(), valueUsage))
             return false;
         break;
 
@@ -10545,7 +10558,7 @@ BytecodeEmitter::emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote)
       case PNK_CALL:
       case PNK_GENEXP:
       case PNK_SUPERCALL:
-        if (!emitCallOrNew(pn))
+        if (!emitCallOrNew(pn, valueUsage))
             return false;
         break;
 
@@ -10703,12 +10716,13 @@ BytecodeEmitter::emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote)
 }
 
 bool
-BytecodeEmitter::emitTreeInBranch(ParseNode* pn)
+BytecodeEmitter::emitTreeInBranch(ParseNode* pn,
+                                  ValueUsage valueUsage /* = ValueUsage::WantValue */)
 {
     // Code that may be conditionally executed always need their own TDZ
     // cache.
     TDZCheckCache tdzCache(this);
-    return emitTree(pn);
+    return emitTree(pn, valueUsage);
 }
 
 static bool
diff --git a/js/src/frontend/BytecodeEmitter.h b/js/src/frontend/BytecodeEmitter.h
index 4e5209593a..99d6a2ff7a 100644
--- a/js/src/frontend/BytecodeEmitter.h
+++ b/js/src/frontend/BytecodeEmitter.h
@@ -171,6 +171,11 @@ struct JumpList {
     void patchAll(jsbytecode* code, JumpTarget target);
 };
 
+enum class ValueUsage {
+    WantValue,
+    IgnoreValue
+};
+
 struct MOZ_STACK_CLASS BytecodeEmitter
 {
     class TDZCheckCache;
@@ -434,10 +439,12 @@ struct MOZ_STACK_CLASS BytecodeEmitter
     };
 
     // Emit code for the tree rooted at pn.
-    MOZ_MUST_USE bool emitTree(ParseNode* pn, EmitLineNumberNote emitLineNote = EMIT_LINENOTE);
+    MOZ_MUST_USE bool emitTree(ParseNode* pn, ValueUsage valueUsage = ValueUsage::WantValue,
+                               EmitLineNumberNote emitLineNote = EMIT_LINENOTE);
 
     // Emit code for the tree rooted at pn with its own TDZ cache.
-    MOZ_MUST_USE bool emitTreeInBranch(ParseNode* pn);
+    MOZ_MUST_USE bool emitTreeInBranch(ParseNode* pn,
+                                       ValueUsage valueUsage = ValueUsage::WantValue);
 
     // Emit global, eval, or module code for tree rooted at body. Always
     // encompasses the entire source.
@@ -724,16 +731,18 @@ struct MOZ_STACK_CLASS BytecodeEmitter
     MOZ_MUST_USE bool emitRightAssociative(ParseNode* pn);
     MOZ_MUST_USE bool emitLeftAssociative(ParseNode* pn);
     MOZ_MUST_USE bool emitLogical(ParseNode* pn);
-    MOZ_MUST_USE bool emitSequenceExpr(ParseNode* pn);
+    MOZ_MUST_USE bool emitSequenceExpr(ParseNode* pn,
+                                       ValueUsage valueUsage = ValueUsage::WantValue);
 
     MOZ_NEVER_INLINE MOZ_MUST_USE bool emitIncOrDec(ParseNode* pn);
 
-    MOZ_MUST_USE bool emitConditionalExpression(ConditionalExpression& conditional);
+    MOZ_MUST_USE bool emitConditionalExpression(ConditionalExpression& conditional,
+                                                ValueUsage valueUsage = ValueUsage::WantValue);
 
     MOZ_MUST_USE bool isRestParameter(ParseNode* pn, bool* result);
     MOZ_MUST_USE bool emitOptimizeSpread(ParseNode* arg0, JumpList* jmp, bool* emitted);
 
-    MOZ_MUST_USE bool emitCallOrNew(ParseNode* pn);
+    MOZ_MUST_USE bool emitCallOrNew(ParseNode* pn, ValueUsage valueUsage = ValueUsage::WantValue);
     MOZ_MUST_USE bool emitSelfHostedCallFunction(ParseNode* pn);
     MOZ_MUST_USE bool emitSelfHostedResumeGenerator(ParseNode* pn);
     MOZ_MUST_USE bool emitSelfHostedForceInterpreter(ParseNode* pn);