[wasm] Trap handling: ProtectedLoad instruction

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index 4c2f6e80dfb78459a22684bf2c7ab9168ca14188..09eda881e6463f31c2ee4799889d3635cdf07ddd 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -9,6 +9,7 @@
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/osr.h"
+#include "src/wasm/wasm-module.h"
 #include "src/x64/assembler-x64.h"
 #include "src/x64/macro-assembler-x64.h"
 
@@ -260,6 +261,40 @@ class OutOfLineRecordWrite final : public OutOfLineCode {
   RecordWriteMode const mode_;
 };
 
+class WasmOutOfLineTrap final : public OutOfLineCode {
+ public:
+  WasmOutOfLineTrap(CodeGenerator* gen, Address pc, bool needs_frame,
+                    Register context, int32_t position)
+      : OutOfLineCode(gen),
+        pc_(pc),
+        needs_frame_(needs_frame),
+        context_(context),
+        position_(position) {}
+
+  void Generate() final {
+    // TODO(eholk): record pc_ and the current pc in a table so that
+    // the signal handler can find it.
+    USE(pc_);
+
+    if (needs_frame_) {
+      __ EnterFrame(StackFrame::WASM);
+    }
+
+    wasm::TrapReason trap_id = wasm::kTrapMemOutOfBounds;
+    int trap_reason = wasm::WasmOpcodes::TrapReasonToMessageId(trap_id);
+    __ Push(Smi::FromInt(trap_reason));
+    __ Push(Smi::FromInt(position_));
+    __ Move(rsi, context_);
+    __ CallRuntime(Runtime::kThrowWasmError);
+  }
+
+ private:
+  Address pc_;
+  bool needs_frame_;
+  Register context_;
+  int32_t position_;
+};
+
 }  // namespace
 
 
@@ -1849,6 +1884,7 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
       break;
     }
     case kX64Movl:
+    case kX64TrapMovl:
       if (instr->HasOutput()) {
         if (instr->addressing_mode() == kMode_None) {
           if (instr->InputAt(0)->IsRegister()) {
@@ -1857,7 +1893,14 @@ CodeGenerator::CodeGenResult CodeGenerator::AssembleArchInstruction(
             __ movl(i.OutputRegister(), i.InputOperand(0));
           }
         } else {
+          Address pc = __ pc();
           __ movl(i.OutputRegister(), i.MemoryOperand());
+
+          if (arch_opcode == kX64TrapMovl) {
+            bool needs_frame = !frame_access_state()->has_frame();

[titzer, 2016/09/08 17:06:35]

Can we invert the sense of this and just call it frame_elided? That way it just
records the state at this load and the out of line code can handle that (by
emitting the prologue).

[Eric Holk, 2016/09/08 21:11:56]

Isn't inverting the sense at odds with calling it frame_elided? Right now, if
needs_frame is true then the out of line code will emit the prologue. I'm fine
with calling it frame_elided, but it seems like we'll have a ! either here or on
line 279 where the value is used.

[titzer, 2016/09/09 15:36:56]

Yes, you are correct, sir!

+            new (zone()) WasmOutOfLineTrap(this, pc, needs_frame,
+                                           i.InputRegister(2), i.InputInt32(3));
+          }
         }
         __ AssertZeroExtended(i.OutputRegister());
       } else {