[wasm-gc][liftoff] Reserve a stack slot for feedback

So far the slot is set to 0; in an upcoming CL it will be
used for an actual feedback vector.

Bug: v8:7748
Change-Id: I79f7502757d2cd8b07ced7105bf7532f5bc9b4f0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3205898
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77279}

src/execution/frames.cc

@@ -968,6 +968,7 @@ void CommonFrame::IterateCompiledFrame(RootVisitor* v) const {
   bool is_wasm = false;
 
 #if V8_ENABLE_WEBASSEMBLY
+  bool has_wasm_feedback_slot = false;
   if (auto* wasm_code = wasm::GetWasmCodeManager()->LookupCode(inner_pointer)) {
     is_wasm = true;
     SafepointTable table(wasm_code);
@@ -978,6 +979,9 @@ void CommonFrame::IterateCompiledFrame(RootVisitor* v) const {
         wasm_code->kind() != wasm::WasmCode::kWasmToCapiWrapper;
     first_tagged_parameter_slot = wasm_code->first_tagged_parameter_slot();
     num_tagged_parameter_slots = wasm_code->num_tagged_parameter_slots();
+    if (wasm_code->is_liftoff() && FLAG_wasm_speculative_inlining) {
+      has_wasm_feedback_slot = true;
+    }
   }
 #endif  // V8_ENABLE_WEBASSEMBLY
 
@@ -1041,6 +1045,7 @@ void CommonFrame::IterateCompiledFrame(RootVisitor* v) const {
       case WASM:
       case WASM_COMPILE_LAZY:
         frame_header_size = WasmFrameConstants::kFixedFrameSizeFromFp;
+        if (has_wasm_feedback_slot) frame_header_size += kSystemPointerSize;
         break;
       case WASM_EXIT:
         // The last value in the frame header is the calling PC, which should

src/flags/flag-definitions.h

@@ -1046,6 +1046,8 @@ DEFINE_BOOL(wasm_math_intrinsics, true,
 DEFINE_BOOL(
     wasm_inlining, false,
     "enable inlining of wasm functions into wasm functions (experimental)")
+DEFINE_BOOL(wasm_speculative_inlining, false,
+            "enable speculative inlining of call_ref targets (experimental)")
 DEFINE_BOOL(wasm_loop_unrolling, true,
             "enable loop unrolling for wasm functions")
 DEFINE_BOOL(wasm_fuzzer_gen_test, false,

src/wasm/baseline/arm/liftoff-assembler-arm.h

@@ -57,17 +57,19 @@ inline constexpr Condition ToCondition(LiftoffCondition liftoff_cond) {
 //  -----+--------------------+  <-- frame ptr (fp)
 //  -1   | 0xa: WASM          |
 //  -2   |     instance       |
+//  -3   |    feedback vector |
 //  -----+--------------------+---------------------------
-//  -3   |    slot 0 (high)   |   ^
-//  -4   |    slot 0 (low)    |   |
-//  -5   |    slot 1 (high)   | Frame slots
-//  -6   |    slot 1 (low)    |   |
+//  -4   |    slot 0 (high)   |   ^
+//  -5   |    slot 0 (low)    |   |
+//  -6   |    slot 1 (high)   | Frame slots
+//  -7   |    slot 1 (low)    |   |
 //       |                    |   v
 //  -----+--------------------+  <-- stack ptr (sp)
 //
 static_assert(2 * kSystemPointerSize == LiftoffAssembler::kStackSlotSize,
               "Slot size should be twice the size of the 32 bit pointer.");
 constexpr int kInstanceOffset = 2 * kSystemPointerSize;
+constexpr int kFeedbackVectorOffset = 3 * kSystemPointerSize;
 // kPatchInstructionsRequired sets a maximum limit of how many instructions that
 // PatchPrepareStackFrame will use in order to increase the stack appropriately.
 // Three instructions are required to sub a large constant, movw + movt + sub.
@@ -557,7 +559,7 @@ void LiftoffAssembler::AbortCompilation() { AbortedCodeGeneration(); }
 
 // static
 constexpr int LiftoffAssembler::StaticStackFrameSize() {
-  return liftoff::kInstanceOffset;
+  return liftoff::kFeedbackVectorOffset;
 }
 
 int LiftoffAssembler::SlotSizeForType(ValueKind kind) {

src/wasm/baseline/arm64/liftoff-assembler-arm64.h

@@ -57,9 +57,10 @@ inline constexpr Condition ToCondition(LiftoffCondition liftoff_cond) {
 //  -----+--------------------+  <-- frame ptr (fp)
 //  -1   | 0xa: WASM          |
 //  -2   |     instance       |
+//  -3   |     feedback vector|
 //  -----+--------------------+---------------------------
-//  -3   |     slot 0         |   ^
-//  -4   |     slot 1         |   |
+//  -4   |     slot 0         |   ^
+//  -5   |     slot 1         |   |
 //       |                    | Frame slots
 //       |                    |   |
 //       |                    |   v
@@ -68,6 +69,7 @@ inline constexpr Condition ToCondition(LiftoffCondition liftoff_cond) {
 //
 
 constexpr int kInstanceOffset = 2 * kSystemPointerSize;
+constexpr int kFeedbackVectorOffset = 3 * kSystemPointerSize;
 
 inline MemOperand GetStackSlot(int offset) { return MemOperand(fp, -offset); }
 
@@ -384,7 +386,7 @@ void LiftoffAssembler::AbortCompilation() { AbortedCodeGeneration(); }
 
 // static
 constexpr int LiftoffAssembler::StaticStackFrameSize() {
-  return liftoff::kInstanceOffset;
+  return liftoff::kFeedbackVectorOffset;
 }
 
 int LiftoffAssembler::SlotSizeForType(ValueKind kind) {

src/wasm/baseline/ia32/liftoff-assembler-ia32.h

@@ -51,6 +51,7 @@ inline constexpr Condition ToCondition(LiftoffCondition liftoff_cond) {
 
 // ebp-4 holds the stack marker, ebp-8 is the instance parameter.
 constexpr int kInstanceOffset = 8;
+constexpr int kFeedbackVectorOffset = 12;  // ebp-12 is the feedback vector.
 
 inline Operand GetStackSlot(int offset) { return Operand(ebp, -offset); }
 
@@ -307,7 +308,7 @@ void LiftoffAssembler::AbortCompilation() {}
 
 // static
 constexpr int LiftoffAssembler::StaticStackFrameSize() {
-  return liftoff::kInstanceOffset;
+  return liftoff::kFeedbackVectorOffset;
 }
 
 int LiftoffAssembler::SlotSizeForType(ValueKind kind) {

src/wasm/baseline/liftoff-compiler.cc

@@ -752,6 +752,12 @@ class LiftoffCompiler {
                   descriptor_->GetInputLocation(kInstanceParameterIndex)
                       .AsRegister()));
     __ cache_state()->SetInstanceCacheRegister(kWasmInstanceRegister);
+    // Load the feedback vector and cache it in a stack slot.
+    if (FLAG_wasm_speculative_inlining) {
+      UNIMPLEMENTED();
+    } else {
+      __ Spill(liftoff::kFeedbackVectorOffset, WasmValue::ForUintPtr(0));
+    }
     if (for_debugging_) __ ResetOSRTarget();
 
     // Process parameters.
@@ -2205,7 +2211,7 @@ class LiftoffCompiler {
       state.dec_used(slot_reg);
       dst_slot->MakeStack();
     }
-    DCHECK_EQ(kind, __ local_kind(local_index));
+    DCHECK(CheckCompatibleStackSlotTypes(kind, __ local_kind(local_index)));
     RegClass rc = reg_class_for(kind);
     LiftoffRegister dst_reg = __ GetUnusedRegister(rc, {});
     __ Fill(dst_reg, src_slot.offset(), kind);

src/wasm/baseline/x64/liftoff-assembler-x64.h

@@ -65,6 +65,7 @@ static_assert((kLiftoffAssemblerFpCacheRegs &
 
 // rbp-8 holds the stack marker, rbp-16 is the instance parameter.
 constexpr int kInstanceOffset = 16;
+constexpr int kFeedbackVectorOffset = 24;  // rbp-24 is the feedback vector.
 
 inline Operand GetStackSlot(int offset) { return Operand(rbp, -offset); }