From 411cba1314e4219a16185093448471c14c22fc6f Mon Sep 17 00:00:00 2001
From: Protobuf Team Bot <protobuf-github-bot@google.com>
Date: Tue, 1 Nov 2022 15:03:32 -0700
Subject: [PATCH] Call ParseVarint with a pointer to the specific result
 instead of always passing in a uint64_t * when possible.

Specialize ParseVarint for bool, which then takes up much less code.

PiperOrigin-RevId: 485427698
---
 .../generated_message_tctable_lite.cc         | 84 +++++++++++++++++--
 1 file changed, 76 insertions(+), 8 deletions(-)

diff --git a/src/google/protobuf/generated_message_tctable_lite.cc b/src/google/protobuf/generated_message_tctable_lite.cc
index cb4f2cbab7..e146aefe42 100644
--- a/src/google/protobuf/generated_message_tctable_lite.cc
+++ b/src/google/protobuf/generated_message_tctable_lite.cc
@@ -789,31 +789,99 @@ done10:
   return {p + 10, res1 & res2 & res3};
 }
 
+template <class Type>
 inline PROTOBUF_ALWAYS_INLINE const char* ParseVarint(const char* p,
-                                                      uint64_t* value) {
+                                                      Type* value) {
+  static_assert(sizeof(Type) == 4 || sizeof(Type) == 8,
+                "Only [u]int32_t and [u]int64_t please");
   int64_t byte = static_cast<int8_t>(*p);
   if (PROTOBUF_PREDICT_TRUE(byte >= 0)) {
     *value = byte;
     return p + 1;
   } else {
     auto tmp = Parse64FallbackPair(p, byte);
-    if (PROTOBUF_PREDICT_TRUE(tmp.first)) *value = tmp.second;
+    if (PROTOBUF_PREDICT_TRUE(tmp.first)) {
+      *value = static_cast<Type>(tmp.second);
+    }
     return tmp.first;
   }
 }
 
+// This overload is specifically for handling bool, because bools have very
+// different requirements and performance opportunities than ints.
+inline PROTOBUF_ALWAYS_INLINE const char* ParseVarint(const char* p,
+                                                      bool* value) {
+  unsigned char byte = static_cast<unsigned char>(*p++);
+  if (PROTOBUF_PREDICT_TRUE(byte == 0 || byte == 1)) {
+    // This is the code path almost always taken,
+    // so we take care to make it very efficient.
+    if (sizeof(byte) == sizeof(*value)) {
+      memcpy(value, &byte, 1);
+    } else {
+      // The C++ standard does not specify that a `bool` takes only one byte
+      *value = byte;
+    }
+    return p;
+  }
+  // This part, we just care about code size.
+  // Although it's almost never used, we have to support it because we guarantee
+  // compatibility for users who change a field from an int32 or int64 to a bool
+  if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+    byte = (byte - 0x80) | *p++;
+    if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+      byte = (byte - 0x80) | *p++;
+      if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+        byte = (byte - 0x80) | *p++;
+        if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+          byte = (byte - 0x80) | *p++;
+          if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+            byte = (byte - 0x80) | *p++;
+            if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+              byte = (byte - 0x80) | *p++;
+              if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+                byte = (byte - 0x80) | *p++;
+                if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+                  byte = (byte - 0x80) | *p++;
+                  if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+                    byte = (byte - 0x80) | *p++;
+                    if (PROTOBUF_PREDICT_FALSE(byte & 0x80)) {
+                      return nullptr;
+                    }
+                  }
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+  *value = byte;
+  return p;
+}
+
 template <typename FieldType, bool zigzag = false>
-inline FieldType ZigZagDecodeHelper(uint64_t value) {
+inline FieldType ZigZagDecodeHelper(FieldType value) {
   return static_cast<FieldType>(value);
 }
 
 template <>
-inline int32_t ZigZagDecodeHelper<int32_t, true>(uint64_t value) {
+inline uint32_t ZigZagDecodeHelper<uint32_t, true>(uint32_t value) {
   return WireFormatLite::ZigZagDecode32(value);
 }
 
 template <>
-inline int64_t ZigZagDecodeHelper<int64_t, true>(uint64_t value) {
+inline int32_t ZigZagDecodeHelper<int32_t, true>(int32_t value) {
+  return WireFormatLite::ZigZagDecode32(value);
+}
+
+template <>
+inline uint64_t ZigZagDecodeHelper<uint64_t, true>(uint64_t value) {
+  return WireFormatLite::ZigZagDecode64(value);
+}
+
+template <>
+inline int64_t ZigZagDecodeHelper<int64_t, true>(int64_t value) {
   return WireFormatLite::ZigZagDecode64(value);
 }
 
@@ -868,11 +936,11 @@ PROTOBUF_NOINLINE const char* TcParser::SingularVarBigint(
 #if defined(__GNUC__)
   // This empty asm block convinces the compiler that the contents of spill may
   // have changed, and thus can't be cached in registers.  It's similar to, but
-  // more optimal then, the effect of declaring it "volatile".
+  // more optimal than, the effect of declaring it "volatile".
   asm("" : "+m"(spill));
 #endif
 
-  uint64_t tmp;
+  FieldType tmp;
   PROTOBUF_ASSUME(static_cast<int8_t>(*ptr) < 0);
   ptr = ParseVarint(ptr, &tmp);
 
@@ -946,7 +1014,7 @@ PROTOBUF_ALWAYS_INLINE const char* TcParser::RepeatedVarint(
   const auto expected_tag = UnalignedLoad<TagType>(ptr);
   do {
     ptr += sizeof(TagType);
-    uint64_t tmp;
+    FieldType tmp;
     ptr = ParseVarint(ptr, &tmp);
     if (ptr == nullptr) {
       return Error(PROTOBUF_TC_PARAM_PASS);