Explicitly initialize opaque pointer mode in CodeGenAction

[MatzeB]

Summary

Explicitly call LLVMContext::setOpaquePointers in CodeGenAction before loading any IR files. With this we use the mode specified on the command-line rather than lazily initializing it based on the contents of the IR.

This helps when using -fthinlto-index which may end up mixing files with typed and opaque pointer types which fails when the first file happened to use typed pointers since we cannot downgrade IR with opaque pointer types to typed pointer types.

[nikic]

clang/lib/CodeGen/CodeGenAction.cpp

1112

I think it would be fine to always do this, not just for the ThinLTO case.

clang/test/CodeGen/thinlto-opaque-typed-mix.ll

14

What's the false doing here?

[MatzeB]

address review feedback.

[nikic]

LG

clang/lib/CodeGen/CodeGenAction.cpp

if (!CI.getCodeGenOpts().ThinLTOIndexFile.empty()) {
     // possible if ThinLTO compilation was not able to split module. Content of
     // the file was already processed by indexing and will be passed to the
     // linker using merged object file.
     if (!Bm) {
       auto M = std::make_unique<llvm::Module>("empty", *VMContext);
       M->setTargetTriple(CI.getTargetOpts().Triple);
       return M;
     }
+
+    // For ThinLTO explicitely set opaque pointer mode to avoid problems when
+    // mixing opaque pointers and typed pointers bitcode files.
+    VMContext->setOpaquePointers(CI.getCodeGenOpts().OpaquePointers);
+
     Expected<std::unique_ptr<llvm::Module>> MOrErr =
         Bm->parseModule(*VMContext);
     if (!MOrErr)
       return DiagErrors(MOrErr.takeError());
     return std::move(*MOrErr);
   }
 
   llvm::SMDiagnostic Err;

clang/test/CodeGen/Inputs/thinlto-opaque.ll

+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--"
+
+define ptr @f2() {
+  ret ptr null
+}

clang/test/CodeGen/thinlto-opaque-typed-mix.ll

+; REQUIRES: x86-registered-target
+; Test that mixing bitcode file with opaque and typed pointers works.
+
+; RUN: mkdir -p %t
+; RUN: opt -module-summary -o %t/typed.bc %s
+; RUN: opt -module-summary -o %t/opaque.bc %S/Inputs/thinlto-opaque.ll
+; RUN: llvm-lto2 run -thinlto-distributed-indexes %t/typed.bc %t/opaque.bc \
+; RUN:   -o %t/native.o -r %t/typed.bc,main,plx -r %t/typed.bc,f2, \
+; RUN:   -r %t/opaque.bc,f2,p
+
+; RUN: %clang_cc1 -triple x86_64-- -emit-obj -o %t/native.o %t/typed.bc \
+; RUN:   -Wno-override-module \
+; RUN:   -fthinlto-index=%t/typed.bc.thinlto.bc
+; RUN: false
+
+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--"
+
+declare i8* @f2()
+
+define i32 @main() {
+  call i8* @f2()
+  ret i32 0
+}