Mesa (main): clc: Declare LLVMContexts on the stack

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Module: Mesa
Branch: main
Commit: 46d9b0e431a890e4f130f6cd3e2e150b152f51f1
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=46d9b0e431a890e4f130f6cd3e2e150b152f51f1

Author: Jason Ekstrand <jason.ekstrand at collabora.com>
Date:   Wed Apr 13 16:52:17 2022 -0500

clc: Declare LLVMContexts on the stack

This prevents more use-after-free errors.  Passing them around using
std::unique_ptr ensures that the LLVMContext gets destroyed but doesn't
ensure destruction order.  Declaring it on the stack ensures that the
context doesn't get destroyed until right before the the function
returns which is after any other LLVM stuff is destroyed.

Reviewed-by: Jesse Natalie <jenatali at microsoft.com>
Reviewed-by: Icecream95 <ixn at disroot.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15937>

---

 src/compiler/clc/clc_helpers.cpp | 50 ++++++++++++++++++++++++----------------
 1 file changed, 30 insertions(+), 20 deletions(-)

diff --git a/src/compiler/clc/clc_helpers.cpp b/src/compiler/clc/clc_helpers.cpp
index 7e4ae62b440..01ef8a66e4a 100644
--- a/src/compiler/clc/clc_helpers.cpp
+++ b/src/compiler/clc/clc_helpers.cpp
@@ -747,16 +747,11 @@ clc_free_kernels_info(const struct clc_kernel_info *kernels,
    free((void *)kernels);
 }
 
-static std::pair<std::unique_ptr<::llvm::Module>, std::unique_ptr<LLVMContext>>
-clc_compile_to_llvm_module(const struct clc_compile_args *args,
+static std::unique_ptr<::llvm::Module>
+clc_compile_to_llvm_module(LLVMContext &llvm_ctx,
+                           const struct clc_compile_args *args,
                            const struct clc_logger *logger)
 {
-   clc_initialize_llvm();
-
-   std::unique_ptr<LLVMContext> llvm_ctx { new LLVMContext };
-   llvm_ctx->setDiagnosticHandlerCallBack(llvm_log_handler,
-                                          const_cast<clc_logger *>(logger));
-
    std::string diag_log_str;
    raw_string_ostream diag_log_stream { diag_log_str };
 
@@ -878,14 +873,14 @@ clc_compile_to_llvm_module(const struct clc_compile_args *args,
            ::llvm::MemoryBuffer::getMemBufferCopy(std::string(args->source.value)).release());
 
    // Compile the code
-   clang::EmitLLVMOnlyAction act(llvm_ctx.get());
+   clang::EmitLLVMOnlyAction act(&llvm_ctx);
    if (!c->ExecuteAction(act)) {
       clc_error(logger, "%sError executing LLVM compilation action.\n",
                 diag_log_str.c_str());
       return {};
    }
 
-   return { act.takeModule(), std::move(llvm_ctx) };
+   return act.takeModule();
 }
 
 static SPIRV::VersionNumber
@@ -906,7 +901,7 @@ spirv_version_to_llvm_spirv_translator_version(enum clc_spirv_version version)
 
 static int
 llvm_mod_to_spirv(std::unique_ptr<::llvm::Module> mod,
-                  std::unique_ptr<LLVMContext> context,
+                  LLVMContext &context,
                   const struct clc_compile_args *args,
                   const struct clc_logger *logger,
                   struct clc_binary *out_spirv)
@@ -969,13 +964,19 @@ clc_c_to_spir(const struct clc_compile_args *args,
               const struct clc_logger *logger,
               struct clc_binary *out_spir)
 {
-   auto pair = clc_compile_to_llvm_module(args, logger);
-   if (!pair.first)
+   clc_initialize_llvm();
+
+   LLVMContext llvm_ctx;
+   llvm_ctx.setDiagnosticHandlerCallBack(llvm_log_handler,
+                                         const_cast<clc_logger *>(logger));
+
+   auto mod = clc_compile_to_llvm_module(llvm_ctx, args, logger);
+   if (!mod)
       return -1;
 
    ::llvm::SmallVector<char, 0> buffer;
    ::llvm::BitcodeWriter writer(buffer);
-   writer.writeModule(*pair.first);
+   writer.writeModule(*mod);
 
    out_spir->size = buffer.size_in_bytes();
    out_spir->data = malloc(out_spir->size);
@@ -989,10 +990,16 @@ clc_c_to_spirv(const struct clc_compile_args *args,
                const struct clc_logger *logger,
                struct clc_binary *out_spirv)
 {
-   auto pair = clc_compile_to_llvm_module(args, logger);
-   if (!pair.first)
+   clc_initialize_llvm();
+
+   LLVMContext llvm_ctx;
+   llvm_ctx.setDiagnosticHandlerCallBack(llvm_log_handler,
+                                         const_cast<clc_logger *>(logger));
+
+   auto mod = clc_compile_to_llvm_module(llvm_ctx, args, logger);
+   if (!mod)
       return -1;
-   return llvm_mod_to_spirv(std::move(pair.first), std::move(pair.second), args, logger, out_spirv);
+   return llvm_mod_to_spirv(std::move(mod), llvm_ctx, args, logger, out_spirv);
 }
 
 int
@@ -1002,13 +1009,16 @@ clc_spir_to_spirv(const struct clc_binary *in_spir,
 {
    clc_initialize_llvm();
 
-   std::unique_ptr<LLVMContext> llvm_ctx{ new LLVMContext };
+   LLVMContext llvm_ctx;
+   llvm_ctx.setDiagnosticHandlerCallBack(llvm_log_handler,
+                                         const_cast<clc_logger *>(logger));
+
    ::llvm::StringRef spir_ref(static_cast<const char*>(in_spir->data), in_spir->size);
-   auto mod = ::llvm::parseBitcodeFile(::llvm::MemoryBufferRef(spir_ref, "<spir>"), *llvm_ctx);
+   auto mod = ::llvm::parseBitcodeFile(::llvm::MemoryBufferRef(spir_ref, "<spir>"), llvm_ctx);
    if (!mod)
       return -1;
 
-   return llvm_mod_to_spirv(std::move(mod.get()), std::move(llvm_ctx), NULL, logger, out_spirv);
+   return llvm_mod_to_spirv(std::move(mod.get()), llvm_ctx, NULL, logger, out_spirv);
 }
 
 class SPIRVMessageConsumer {