[wasm] Fix --no-wasm-bounds-checks flag

If bounds checks are completely disabled (for performance testing) we
would still emit protected instructions which generate landing pads for
trap handlers in code generation. This CL fixes that by implicitly
disabling trap handling if stack checks are disabled.

R=ahaas@chromium.org

Bug: v8:10949
Change-Id: I1172087fb14ab56e9117c6eee388f71099568a13
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2808946Reviewed-by: Maya Lekova <mslekova@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73832}

src/compiler/backend/arm64/code-generator-arm64.cc

@@ -438,6 +438,7 @@ class WasmProtectedInstructionTrap final : public WasmOutOfLineTrap {
       : WasmOutOfLineTrap(gen, instr), pc_(pc) {}
 
   void Generate() override {
+    DCHECK(FLAG_wasm_bounds_checks && FLAG_wasm_trap_handler);
     gen_->AddProtectedInstructionLanding(pc_, __ pc_offset());
     GenerateWithTrapId(TrapId::kTrapMemOutOfBounds);
   }

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

@@ -376,6 +376,7 @@ class WasmProtectedInstructionTrap final : public WasmOutOfLineTrap {
       : WasmOutOfLineTrap(gen, instr), pc_(pc) {}
 
   void Generate() final {
+    DCHECK(FLAG_wasm_bounds_checks && FLAG_wasm_trap_handler);
     gen_->AddProtectedInstructionLanding(pc_, __ pc_offset());
     GenerateWithTrapId(TrapId::kTrapMemOutOfBounds);
   }

src/flags/flag-definitions.h

@@ -965,6 +965,8 @@ DEFINE_BOOL(wasm_loop_unrolling, false,
 DEFINE_BOOL(wasm_trap_handler, true,
             "use signal handlers to catch out of bounds memory access in wasm"
             " (currently Linux x86_64 only)")
+// "no bounds checks" implies "no trap handlers".
+DEFINE_NEG_NEG_IMPLICATION(wasm_bounds_checks, wasm_trap_handler)
 DEFINE_BOOL(wasm_fuzzer_gen_test, false,
             "generate a test case when running a wasm fuzzer")
 DEFINE_IMPLICATION(wasm_fuzzer_gen_test, single_threaded)