[llvm] e95ad93 - [llvm-dis] Add an option `dump-thinlto-index-only` in llvm-dis to read ThinLTO minimized code only.

[via llvm-commits]

Author: minglotus-6
Date: 2022-01-19T18:07:50-08:00
New Revision: e95ad93e6ef874ad208028c18b4cb4890320f25c

URL: https://github.com/llvm/llvm-project/commit/e95ad93e6ef874ad208028c18b4cb4890320f25c
DIFF: https://github.com/llvm/llvm-project/commit/e95ad93e6ef874ad208028c18b4cb4890320f25c.diff

LOG: [llvm-dis] Add an option `dump-thinlto-index-only` in llvm-dis to read ThinLTO minimized code only.

Added: 
    llvm/test/Bitcode/thinlto-index-disassembled-by-llvm-dis.ll

Modified: 
    llvm/lib/Bitcode/Reader/BitcodeReader.cpp
    llvm/tools/llvm-dis/llvm-dis.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 9e414aa74dc7c..1e60bad616979 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -3835,6 +3835,11 @@ Error BitcodeReader::parseModule(uint64_t ResumeBit,
       if (Error Err = parseComdatRecord(Record))
         return Err;
       break;
+    // FIXME: BitcodeReader should handle {GLOBALVAR, FUNCTION, ALIAS, IFUNC}
+    // written by ThinLinkBitcodeWriter. See
+    // `ThinLinkBitcodeWriter::writeSimplifiedModuleInfo` for the format of each
+    // record
+    // (https://github.com/llvm/llvm-project/blob/b6a93967d9c11e79802b5e75cec1584d6c8aa472/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp#L4714)
     case bitc::MODULE_CODE_GLOBALVAR:
       if (Error Err = parseGlobalVarRecord(Record))
         return Err;

diff  --git a/llvm/test/Bitcode/thinlto-index-disassembled-by-llvm-dis.ll b/llvm/test/Bitcode/thinlto-index-disassembled-by-llvm-dis.ll
new file mode 100644
index 0000000000000..ca18a912f9fa4
--- /dev/null
+++ b/llvm/test/Bitcode/thinlto-index-disassembled-by-llvm-dis.ll
@@ -0,0 +1,30 @@
+; Tests that `llvm-dis` could disassemble ThinLTO minimized bitcode
+; (e.g., bitcode generated by `opt --thin-link-bitcode-file=<minimized-bitcode>`,
+;  or `clang -Xclang -fthin-link-bitcode=<minimized-bitcode>`)
+
+; %t.o is the thin-lto ready bitcode, and %t.thinlink.bc is the minimized bitcode. 
+; RUN: opt -thinlto-bc %s -thin-link-bitcode-file=%t.thinlink.bc -o %t.o
+
+; With default options, `llvm-dis` returns invalid record for ThinLTO minimized bitcode.
+; RUN: not llvm-dis %t.thinlink.bc 2>&1 | FileCheck %s --check-prefix=INVALID-RECORD
+
+; INVALID-RECORD: Invalid record
+
+; Tests that `llvm-dis` could disassemble minimized bitcode with `--print-thinlto-index-only`, and verify its content.
+; RUN: llvm-dis --print-thinlto-index-only %t.thinlink.bc -o - | FileCheck %s --check-prefix=DIS
+
+; Tests that `llvm-dis` could disassemble ThinLTO-ready bitcode with `--print-thinlto-index-only`,
+; and verify its content.
+; RUN: llvm-dis --print-thinlto-index-only %t.o -o - | FileCheck %s --check-prefix=DIS
+
+; DIS: ^0 = module: (path: "{{.*}}thinlto-index-disassembled-by-llvm-dis.ll.tmp
+; DIS: ^1 = gv: (name: "aplusb", summaries: (function: (module: ^0, flags: (linkage: external, visibility: default, notEligibleToImport: 0, live: 0, dsoLocal: 0, canAutoHide: 0), insts: 2))) ; guid = 
+; DIS: ^2 = blockcount: 1
+
+source_filename = "add.cpp"
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+define i32 @aplusb(i32 %a, i32 %b) {
+  %add = add i32 %b, %a
+  ret i32 %add
+}

diff  --git a/llvm/tools/llvm-dis/llvm-dis.cpp b/llvm/tools/llvm-dis/llvm-dis.cpp
index 62d165fb84135..7b3c3e7706a69 100644
--- a/llvm/tools/llvm-dis/llvm-dis.cpp
+++ b/llvm/tools/llvm-dis/llvm-dis.cpp
@@ -74,6 +74,11 @@ static cl::opt<bool>
                                  "then materialize only the metadata"),
                         cl::cat(DisCategory));
 
+static cl::opt<bool> PrintThinLTOIndexOnly(
+    "print-thinlto-index-only",
+    cl::desc("Only read thinlto index and print the index as LLVM assembly."),
+    cl::init(false), cl::Hidden, cl::cat(DisCategory));
+
 namespace {
 
 static void printDebugLoc(const DebugLoc &DL, formatted_raw_ostream &OS) {
@@ -186,12 +191,17 @@ int main(int argc, char **argv) {
 
     for (size_t I = 0; I < N; ++I) {
       BitcodeModule MB = IF.Mods[I];
-      std::unique_ptr<Module> M = ExitOnErr(
-          MB.getLazyModule(Context, MaterializeMetadata, SetImporting));
-      if (MaterializeMetadata)
-        ExitOnErr(M->materializeMetadata());
-      else
-        ExitOnErr(M->materializeAll());
+
+      std::unique_ptr<Module> M;
+
+      if (!PrintThinLTOIndexOnly) {
+        M = ExitOnErr(
+            MB.getLazyModule(Context, MaterializeMetadata, SetImporting));
+        if (MaterializeMetadata)
+          ExitOnErr(M->materializeMetadata());
+        else
+          ExitOnErr(M->materializeAll());
+      }
 
       BitcodeLTOInfo LTOInfo = ExitOnErr(MB.getLTOInfo());
       std::unique_ptr<ModuleSummaryIndex> Index;
@@ -233,7 +243,8 @@ int main(int argc, char **argv) {
 
       // All that llvm-dis does is write the assembly to a file.
       if (!DontPrint) {
-        M->print(Out->os(), Annotator.get(), PreserveAssemblyUseListOrder);
+        if (M)
+          M->print(Out->os(), Annotator.get(), PreserveAssemblyUseListOrder);
         if (Index)
           Index->print(Out->os());
       }