Rollup merge of #135115 - Zalathar:dwarf-const, r=workingjubilee

cg_llvm: Use constants for DWARF opcodes, instead of FFI calls

Split off from #134009 to incorporate feedback from https://github.com/rust-lang/rust/pull/134009#discussion_r1903133906.

Most of the constant values now come from gimli, which is already a compiler dependency.

I noticed that `DW_OP_LLVM_fragment` is an LLVM detail that is not defined by DWARF and could hypothetically change, so I added a static assertion on the C++ side to detect that if it ever happens.

r? workingjubilee

1 files changed, 4 insertions, 12 deletions

diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index ca62483b0aa..dd72ea2497f 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -54,6 +54,10 @@ using namespace llvm;
 using namespace llvm::sys;
 using namespace llvm::object;
 
+// This opcode is an LLVM detail that could hypothetically change (?), so
+// verify that the hard-coded value in `dwarf_const.rs` still agrees with LLVM.
+static_assert(dwarf::DW_OP_LLVM_fragment == 0x1000);
+
 // LLVMAtomicOrdering is already an enum - don't create another
 // one.
 static AtomicOrdering fromRust(LLVMAtomicOrdering Ordering) {
@@ -1397,18 +1401,6 @@ LLVMRustDILocationCloneWithBaseDiscriminator(LLVMMetadataRef Location,
   return wrap(NewLoc.has_value() ? NewLoc.value() : nullptr);
 }
 
-extern "C" uint64_t LLVMRustDIBuilderCreateOpDeref() {
-  return dwarf::DW_OP_deref;
-}
-
-extern "C" uint64_t LLVMRustDIBuilderCreateOpPlusUconst() {
-  return dwarf::DW_OP_plus_uconst;
-}
-
-extern "C" uint64_t LLVMRustDIBuilderCreateOpLLVMFragment() {
-  return dwarf::DW_OP_LLVM_fragment;
-}
-
 extern "C" void LLVMRustWriteTypeToString(LLVMTypeRef Ty, RustStringRef Str) {
   auto OS = RawRustStringOstream(Str);
   unwrap<llvm::Type>(Ty)->print(OS);