[Liftoff] Add printing for registers and cache state

This prints nicer error messages for checks like
"DCHECK_EQ(reg1, reg2)", and also splits cache state tracing into
one method for printing the overall state, one for printing each slot,
and one for printing the register.

R=titzer@chromium.org

Bug: v8:6600
Change-Id: I36e83ba2542986dd8ad17dbfe7cbb8df54a56755
Reviewed-on: https://chromium-review.googlesource.com/853495
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50407}

src/assembler.h

@@ -36,6 +36,7 @@
 #define V8_ASSEMBLER_H_
 
 #include <forward_list>
+#include <iosfwd>
 
 #include "src/allocation.h"
 #include "src/builtins/builtins.h"
@@ -1338,6 +1339,12 @@ class RegisterBase {
   int reg_code_;
 };
 
+template <typename SubType, int kAfterLastRegister>
+inline std::ostream& operator<<(std::ostream& os,
+                                RegisterBase<SubType, kAfterLastRegister> reg) {
+  return reg.is_valid() ? os << "r" << reg.code() : os << "<invalid reg>";
+}
+
 }  // namespace internal
 }  // namespace v8
 #endif  // V8_ASSEMBLER_H_

src/wasm/baseline/liftoff-assembler.cc

@@ -391,6 +391,19 @@ uint32_t LiftoffAssembler::GetTotalFrameSlotCount() const {
   return num_locals() + kMaxValueStackHeight;
 }
 
+std::ostream& operator<<(std::ostream& os, VarState slot) {
+  os << WasmOpcodes::TypeName(slot.type()) << ":";
+  switch (slot.loc()) {
+    case VarState::kStack:
+      return os << "s";
+    case VarState::kRegister:
+      return os << slot.reg();
+    case VarState::kConstant:
+      return os << "c" << slot.i32_const();
+  }
+  UNREACHABLE();
+}
+
 #undef __
 #undef TRACE
 

src/wasm/baseline/liftoff-assembler.h

@@ -5,6 +5,7 @@
 #ifndef V8_WASM_BASELINE_LIFTOFF_ASSEMBLER_H_
 #define V8_WASM_BASELINE_LIFTOFF_ASSEMBLER_H_
 
+#include <iosfwd>
 #include <memory>
 
 // Clients of this interface shouldn't depend on lots of compiler internals.
@@ -338,6 +339,8 @@ class LiftoffAssembler : public TurboAssembler {
   LiftoffRegister SpillOneRegister(RegClass rc, LiftoffRegList pinned);
 };
 
+std::ostream& operator<<(std::ostream& os, LiftoffAssembler::VarState);
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8

src/wasm/baseline/liftoff-compiler.cc

@@ -771,35 +771,21 @@ class LiftoffCompiler {
   void TraceCacheState(Decoder* decoder) const {
 #ifdef DEBUG
     if (!FLAG_trace_liftoff) return;
+    OFStream os(stdout);
     for (int control_depth = decoder->control_depth() - 1; control_depth >= -1;
          --control_depth) {
       LiftoffAssembler::CacheState* cache_state =
           control_depth == -1
               ? asm_->cache_state()
               : &decoder->control_at(control_depth)->label_state;
-      int idx = 0;
+      bool first = true;
       for (LiftoffAssembler::VarState& slot : cache_state->stack_state) {
-        if (idx++) PrintF("-");
-        PrintF("%s:", WasmOpcodes::TypeName(slot.type()));
-        switch (slot.loc()) {
-          case kStack:
-            PrintF("s");
-            break;
-          case kRegister:
-            if (slot.reg().is_gp()) {
-              PrintF("gp%d", slot.reg().gp().code());
-            } else {
-              PrintF("fp%d", slot.reg().fp().code());
-            }
-            break;
-          case kConstant:
-            PrintF("c");
-            break;
-        }
+        os << (first ? "" : "-") << slot;
+        first = false;
       }
       if (control_depth != -1) PrintF("; ");
     }
-    PrintF("\n");
+    os << "\n";
 #endif
   }
 };

src/wasm/baseline/liftoff-register.h

@@ -5,6 +5,7 @@
 #ifndef V8_WASM_BASELINE_LIFTOFF_REGISTER_H_
 #define V8_WASM_BASELINE_LIFTOFF_REGISTER_H_
 
+#include <iosfwd>
 #include <memory>
 
 // Clients of this interface shouldn't depend on lots of compiler internals.
@@ -107,6 +108,11 @@ class LiftoffRegister {
 static_assert(IS_TRIVIALLY_COPYABLE(LiftoffRegister),
               "LiftoffRegister can efficiently be passed by value");
 
+inline std::ostream& operator<<(std::ostream& os, LiftoffRegister reg) {
+  return reg.is_gp() ? os << "gp" << reg.gp().code()
+                     : os << "fp" << reg.fp().code();
+}
+
 class LiftoffRegList {
  public:
   static constexpr bool use_u16 = kAfterMaxLiftoffRegCode <= 16;