Add disassembler option to show byte offset

The option is disabled by default.

The offset is printed in hex, as a comment after each instruction.

include/libspirv/libspirv.h

@@ -251,6 +251,7 @@ typedef enum spv_binary_to_text_options_t {
   SPV_BINARY_TO_TEXT_OPTION_PRINT = SPV_BIT(1),
   SPV_BINARY_TO_TEXT_OPTION_COLOR = SPV_BIT(2),
   SPV_BINARY_TO_TEXT_OPTION_INDENT = SPV_BIT(3),
+  SPV_BINARY_TO_TEXT_OPTION_SHOW_BYTE_OFFSET = SPV_BIT(4),
   SPV_FORCE_32_BIT_ENUM(spv_binary_to_text_options_t)
 } spv_binary_to_text_options_t;
 

source/disassemble.cpp

@@ -29,6 +29,7 @@
 
 #include <cassert>
 #include <cstring>
+#include <iomanip>
 #include <unordered_map>
 
 #include "assembly_grammar.h"
@@ -48,8 +49,7 @@ namespace {
 // representation.
 class Disassembler {
  public:
-  Disassembler(const libspirv::AssemblyGrammar& grammar,
-               uint32_t options)
+  Disassembler(const libspirv::AssemblyGrammar& grammar, uint32_t options)
       : grammar_(grammar),
         print_(spvIsInBitfield(SPV_BINARY_TO_TEXT_OPTION_PRINT, options)),
         color_(print_ &&
@@ -59,7 +59,10 @@ class Disassembler {
                     : 0),
         text_(),
         out_(print_ ? out_stream() : out_stream(text_)),
-        stream_(out_.get()) {}
+        stream_(out_.get()),
+        show_byte_offset_(spvIsInBitfield(
+            SPV_BINARY_TO_TEXT_OPTION_SHOW_BYTE_OFFSET, options)),
+        byte_offset_(0) {}
 
   // Emits the assembly header for the module, and sets up internal state
   // so subsequent callbacks can handle the cases where the entire module
@@ -120,6 +123,8 @@ class Disassembler {
   std::stringstream text_;   // Captures the text, if not printing.
   out_stream out_;  // The Output stream.  Either to text_ or standard output.
   std::ostream& stream_;  // The output std::stream.
+  const bool show_byte_offset_;  // Should we print byte offset, in hex?
+  size_t byte_offset_; // The number of bytes processed so far.
 };
 
 spv_result_t Disassembler::HandleHeader(spv_endianness_t endian,
@@ -145,6 +150,8 @@ spv_result_t Disassembler::HandleHeader(spv_endianness_t endian,
           << "; Schema: " << schema << "\n";
   ResetColor();
 
+  byte_offset_ = SPV_INDEX_INSTRUCTION * sizeof(uint32_t);
+
   return SPV_SUCCESS;
 }
 
@@ -185,6 +192,19 @@ spv_result_t Disassembler::HandleInstruction(
     EmitOperand(inst, i);
   }
 
+  if (show_byte_offset_) {
+    SetGrey();
+    auto saved_flags = stream_.flags();
+    auto saved_fill = stream_.fill();
+    stream_ << " ; 0x" << std::setw(8) << std::hex << std::setfill('0')
+            << byte_offset_;
+    stream_.flags(saved_flags);
+    stream_.fill(saved_fill);
+    ResetColor();
+  }
+
+  byte_offset_ += inst.num_words * sizeof(uint32_t);
+
   stream_ << "\n";
   return SPV_SUCCESS;
 }

test/BinaryToText.cpp

@@ -392,6 +392,24 @@ OpStore %2 %3 Aligned|Volatile 4 ; bogus, but not indented
       expected);
 }
 
+TEST_F(TextToBinaryTest, ShowByteOffsetsWhenRequested) {
+  const std::string input = R"(
+OpCapability Shader
+OpMemoryModel Logical GLSL450
+%1 = OpTypeInt 32 0
+%2 = OpTypeVoid
+)";
+  const std::string expected =
+      R"(OpCapability Shader ; 0x00000014
+OpMemoryModel Logical GLSL450 ; 0x0000001c
+%1 = OpTypeInt 32 0 ; 0x00000028
+%2 = OpTypeVoid ; 0x00000038
+)";
+  EXPECT_THAT(EncodeAndDecodeSuccessfully(
+                  input, SPV_BINARY_TO_TEXT_OPTION_SHOW_BYTE_OFFSET),
+              expected);
+}
+
 // Test version string.
 TEST_F(TextToBinaryTest, VersionString) {
   auto words = CompileSuccessfully("");

tools/dis/dis.cpp

@@ -52,6 +52,8 @@ Options:
                   The default when output goes to a file.
 
   --no-indent     Don't indent instructions.
+
+  --offsets       Show byte offsets for each instruction.
 )",
       argv0, argv0);
 }
@@ -65,6 +67,7 @@ int main(int argc, char** argv) {
   allow_color = true;
 #endif
   bool allow_indent = true;
+  bool show_byte_offsets = false;
 
   for (int argi = 1; argi < argc; ++argi) {
     if ('-' == argv[argi][0]) {
@@ -84,6 +87,7 @@ int main(int argc, char** argv) {
           // Long options
           if (0 == strcmp(argv[argi], "--no-color")) allow_color = false;
           if (0 == strcmp(argv[argi], "--no-indent")) allow_indent = false;
+          if (0 == strcmp(argv[argi], "--offsets")) show_byte_offsets = true;
           if (0 == strcmp(argv[argi], "--help")) {
             print_usage(argv[0]);
             return 0;
@@ -114,8 +118,9 @@ int main(int argc, char** argv) {
 
   uint32_t options = SPV_BINARY_TO_TEXT_OPTION_NONE;
 
-  if (allow_indent)
-    options |= SPV_BINARY_TO_TEXT_OPTION_INDENT;
+  if (allow_indent) options |= SPV_BINARY_TO_TEXT_OPTION_INDENT;
+
+  if (show_byte_offsets) options |= SPV_BINARY_TO_TEXT_OPTION_SHOW_BYTE_OFFSET;
 
   if (!outFile || (0 == strcmp("-", outFile))) {
     // Print to standard output.