[wasm] TrapIf and TrapUnless TurboFan operators implemented on arm.

Original commit message:
[wasm] Introduce the TrapIf and TrapUnless operators to generate trap code.

Some instructions in WebAssembly trap for some inputs, which means that the
execution is terminated and (at least at the moment) a JavaScript exception is
thrown. Examples for traps are out-of-bounds memory accesses, or integer
divisions by zero.

Without the TrapIf and TrapUnless operators trap check in WebAssembly introduces 5
TurboFan nodes (branch, if_true, if_false, trap-reason constant, trap-position
constant), in addition to the trap condition itself. Additionally, each
WebAssembly function has four TurboFan nodes (merge, effect_phi, 2 phis) whose
number of inputs is linear to the number of trap checks in the function.
Especially for functions with high numbers of trap checks we observe a
significant slowdown in compilation time, down to 0.22 MiB/s in the sqlite
benchmark instead of the average of 3 MiB/s in other benchmarks. By introducing
a TrapIf common operator only a single node is necessary per trap check, in
addition to the trap condition. Also the nodes which are shared between trap
checks (merge, effect_phi, 2 phis) would disappear. First measurements suggest a
speedup of 30-50% on average.

This CL only implements TrapIf and TrapUnless on x64. The implementation is also
hidden behind the --wasm-trap-if flag.

Please take a special look at how the source position is transfered from the
instruction selector to the code generator, and at the context that is used for
the runtime call.

R=titzer@chromium.org, v8-arm-ports@googlegroups.com

Review-Url: https://codereview.chromium.org/2584603002
Cr-Commit-Position: refs/heads/master@{#41774}

src/bailout-reason.h

@@ -265,7 +265,9 @@ namespace internal {
   V(kWrongArgumentCountForInvokeIntrinsic,                                     \
     "Wrong number of arguments for intrinsic")                                 \
   V(kShouldNotDirectlyEnterOsrFunction,                                        \
-    "Should not directly enter OSR-compiled function")
+    "Should not directly enter OSR-compiled function")                         \
+  V(kUnexpectedReturnFromWasmTrap,                                             \
+    "Should not return after throwing a wasm trap")
 
 #define ERROR_MESSAGES_CONSTANTS(C, T) C,
 enum BailoutReason {

src/compiler/arm/code-generator-arm.cc

@@ -1593,7 +1593,64 @@ void CodeGenerator::AssembleArchJump(RpoNumber target) {
 
 void CodeGenerator::AssembleArchTrap(Instruction* instr,
                                      FlagsCondition condition) {
-  UNREACHABLE();
+  class OutOfLineTrap final : public OutOfLineCode {
+   public:
+    OutOfLineTrap(CodeGenerator* gen, bool frame_elided, Instruction* instr)
+        : OutOfLineCode(gen),
+          frame_elided_(frame_elided),
+          instr_(instr),
+          gen_(gen) {}
+
+    void Generate() final {
+      ArmOperandConverter i(gen_, instr_);
+
+      Runtime::FunctionId trap_id = static_cast<Runtime::FunctionId>(
+          i.InputInt32(instr_->InputCount() - 1));
+      bool old_has_frame = __ has_frame();
+      if (frame_elided_) {
+        __ set_has_frame(true);
+        __ EnterFrame(StackFrame::WASM);
+      }
+      GenerateCallToTrap(trap_id);
+      if (frame_elided_) {
+        __ set_has_frame(old_has_frame);
+      }
+      if (FLAG_debug_code) {
+        __ stop(GetBailoutReason(kUnexpectedReturnFromWasmTrap));
+      }
+    }
+
+   private:
+    void GenerateCallToTrap(Runtime::FunctionId trap_id) {
+      if (trap_id == Runtime::kNumFunctions) {
+        // We cannot test calls to the runtime in cctest/test-run-wasm.
+        // Therefore we emit a call to C here instead of a call to the runtime.
+        // We use the context register as the scratch register, because we do
+        // not have a context here.
+        __ PrepareCallCFunction(0, 0, cp);
+        __ CallCFunction(
+            ExternalReference::wasm_call_trap_callback_for_testing(isolate()),
+            0);
+      } else {
+        __ Move(cp, isolate()->native_context());
+        gen_->AssembleSourcePosition(instr_);
+        __ CallRuntime(trap_id);
+      }
+      ReferenceMap* reference_map =
+          new (gen_->zone()) ReferenceMap(gen_->zone());
+      gen_->RecordSafepoint(reference_map, Safepoint::kSimple, 0,
+                            Safepoint::kNoLazyDeopt);
+    }
+
+    bool frame_elided_;
+    Instruction* instr_;
+    CodeGenerator* gen_;
+  };
+  bool frame_elided = !frame_access_state()->has_frame();
+  auto ool = new (zone()) OutOfLineTrap(this, frame_elided, instr);
+  Label* tlabel = ool->entry();
+  Condition cc = FlagsConditionToCondition(condition);
+  __ b(cc, tlabel);
 }
 
 // Assembles boolean materializations after an instruction.

src/compiler/arm/instruction-selector-arm.cc

@@ -267,6 +267,9 @@ void VisitBinop(InstructionSelector* selector, Node* node,
   if (cont->IsDeoptimize()) {
     selector->EmitDeoptimize(opcode, output_count, outputs, input_count, inputs,
                              cont->reason(), cont->frame_state());
+  } else if (cont->IsTrap()) {
+    inputs[input_count++] = g.UseImmediate(cont->trap_id());
+    selector->Emit(opcode, output_count, outputs, input_count, inputs);
   } else {
     selector->Emit(opcode, output_count, outputs, input_count, inputs);
   }
@@ -890,6 +893,9 @@ void VisitShift(InstructionSelector* selector, Node* node,
   if (cont->IsDeoptimize()) {
     selector->EmitDeoptimize(opcode, output_count, outputs, input_count, inputs,
                              cont->reason(), cont->frame_state());
+  } else if (cont->IsTrap()) {
+    inputs[input_count++] = g.UseImmediate(cont->trap_id());
+    selector->Emit(opcode, output_count, outputs, input_count, inputs);
   } else {
     selector->Emit(opcode, output_count, outputs, input_count, inputs);
   }
@@ -1257,10 +1263,14 @@ void EmitInt32MulWithOverflow(InstructionSelector* selector, Node* node,
     InstructionOperand in[] = {temp_operand, result_operand, shift_31};
     selector->EmitDeoptimize(opcode, 0, nullptr, 3, in, cont->reason(),
                              cont->frame_state());
-  } else {
-    DCHECK(cont->IsSet());
+  } else if (cont->IsSet()) {
     selector->Emit(opcode, g.DefineAsRegister(cont->result()), temp_operand,
                    result_operand, shift_31);
+  } else {
+    DCHECK(cont->IsTrap());
+    InstructionOperand in[] = {temp_operand, result_operand, shift_31,
+                               g.UseImmediate(cont->trap_id())};
+    selector->Emit(opcode, 0, nullptr, 4, in);
   }
 }
 
@@ -1648,9 +1658,12 @@ void VisitCompare(InstructionSelector* selector, InstructionCode opcode,
   } else if (cont->IsDeoptimize()) {
     selector->EmitDeoptimize(opcode, g.NoOutput(), left, right, cont->reason(),
                              cont->frame_state());
-  } else {
-    DCHECK(cont->IsSet());
+  } else if (cont->IsSet()) {
     selector->Emit(opcode, g.DefineAsRegister(cont->result()), left, right);
+  } else {
+    DCHECK(cont->IsTrap());
+    selector->Emit(opcode, g.NoOutput(), left, right,
+                   g.UseImmediate(cont->trap_id()));
   }
 }
 
@@ -1841,6 +1854,9 @@ void VisitWordCompare(InstructionSelector* selector, Node* node,
   if (cont->IsDeoptimize()) {
     selector->EmitDeoptimize(opcode, output_count, outputs, input_count, inputs,
                              cont->reason(), cont->frame_state());
+  } else if (cont->IsTrap()) {
+    inputs[input_count++] = g.UseImmediate(cont->trap_id());
+    selector->Emit(opcode, output_count, outputs, input_count, inputs);
   } else {
     selector->Emit(opcode, output_count, outputs, input_count, inputs);
   }
@@ -1997,10 +2013,13 @@ void VisitWordCompareZero(InstructionSelector* selector, Node* user,
   } else if (cont->IsDeoptimize()) {
     selector->EmitDeoptimize(opcode, g.NoOutput(), value_operand, value_operand,
                              cont->reason(), cont->frame_state());
-  } else {
-    DCHECK(cont->IsSet());
+  } else if (cont->IsSet()) {
     selector->Emit(opcode, g.DefineAsRegister(cont->result()), value_operand,
                    value_operand);
+  } else {
+    DCHECK(cont->IsTrap());
+    selector->Emit(opcode, g.NoOutput(), value_operand, value_operand,
+                   g.UseImmediate(cont->trap_id()));
   }
 }
 
@@ -2024,9 +2043,18 @@ void InstructionSelector::VisitDeoptimizeUnless(Node* node) {
   VisitWordCompareZero(this, node, node->InputAt(0), &cont);
 }
 
-void InstructionSelector::VisitTrapIf(Node* node) { UNREACHABLE(); }
+void InstructionSelector::VisitTrapIf(Node* node) {
+  FlagsContinuation cont = FlagsContinuation::ForTrap(
+      kNotEqual, OpParameter<Runtime::FunctionId>(node->op()),
+      node->InputAt(1));
+  VisitWordCompareZero(this, node, node->InputAt(0), &cont);
+}
 
-void InstructionSelector::VisitTrapUnless(Node* node) { UNREACHABLE(); }
+void InstructionSelector::VisitTrapUnless(Node* node) {
+  FlagsContinuation cont = FlagsContinuation::ForTrap(
+      kEqual, OpParameter<Runtime::FunctionId>(node->op()), node->InputAt(1));
+  VisitWordCompareZero(this, node, node->InputAt(0), &cont);
+}
 
 void InstructionSelector::VisitSwitch(Node* node, const SwitchInfo& sw) {
   ArmOperandGenerator g(this);

src/compiler/wasm-compiler.cc

@@ -188,7 +188,7 @@ class WasmTrapHelper : public ZoneObject {
     }
   }
 
-#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32
+#if V8_TARGET_ARCH_X64 || V8_TARGET_ARCH_IA32 || V8_TARGET_ARCH_ARM
 #define WASM_TRAP_IF_SUPPORTED
 #endif