Use constants for DWARF opcodes, instead of FFI calls

Author: Zalathar

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -53,6 +53,16 @@ const DW_TAG_auto_variable: c_uint = 0x100;
 #[allow(non_upper_case_globals)]
 const DW_TAG_arg_variable: c_uint = 0x101;
 
+// `DW_OP_*` values taken from:
+// - `llvm/include/llvm/BinaryFormat/Dwarf.def`
+// - `llvm/include/llvm/BinaryFormat/Dwarf.h`
+#[allow(non_upper_case_globals)]
+const DW_OP_deref: u64 = 0x06;
+#[allow(non_upper_case_globals)]
+const DW_OP_plus_uconst: u64 = 0x23;
+#[allow(non_upper_case_globals)]
+const DW_OP_LLVM_fragment: u64 = 0x1000;
+
 /// A context object for maintaining all state needed by the debuginfo module.
 pub(crate) struct CodegenUnitDebugContext<'ll, 'tcx> {
     llmod: &'ll llvm::Module,
@@ -146,28 +156,23 @@ impl<'ll> DebugInfoBuilderMethods for Builder<'_, 'll, '_> {
         fragment: Option<Range<Size>>,
     ) {
         // Convert the direct and indirect offsets and fragment byte range to address ops.
-        // FIXME(eddyb) use `const`s instead of getting the values via FFI,
-        // the values should match the ones in the DWARF standard anyway.
-        let op_deref = || unsafe { llvm::LLVMRustDIBuilderCreateOpDeref() };
-        let op_plus_uconst = || unsafe { llvm::LLVMRustDIBuilderCreateOpPlusUconst() };
-        let op_llvm_fragment = || unsafe { llvm::LLVMRustDIBuilderCreateOpLLVMFragment() };
         let mut addr_ops = SmallVec::<[u64; 8]>::new();
 
         if direct_offset.bytes() > 0 {
-            addr_ops.push(op_plus_uconst());
+            addr_ops.push(DW_OP_plus_uconst);
             addr_ops.push(direct_offset.bytes() as u64);
         }
         for &offset in indirect_offsets {
-            addr_ops.push(op_deref());
+            addr_ops.push(DW_OP_deref);
             if offset.bytes() > 0 {
-                addr_ops.push(op_plus_uconst());
+                addr_ops.push(DW_OP_plus_uconst);
                 addr_ops.push(offset.bytes() as u64);
             }
         }
         if let Some(fragment) = fragment {
             // `DW_OP_LLVM_fragment` takes as arguments the fragment's
             // offset and size, both of them in bits.
-            addr_ops.push(op_llvm_fragment());
+            addr_ops.push(DW_OP_LLVM_fragment);
             addr_ops.push(fragment.start.bits() as u64);
             addr_ops.push((fragment.end - fragment.start).bits() as u64);
         }

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -2237,9 +2237,6 @@ unsafe extern "C" {
         Location: &'a DILocation,
         BD: c_uint,
     ) -> Option<&'a DILocation>;
-    pub fn LLVMRustDIBuilderCreateOpDeref() -> u64;
-    pub fn LLVMRustDIBuilderCreateOpPlusUconst() -> u64;
-    pub fn LLVMRustDIBuilderCreateOpLLVMFragment() -> u64;
 
     pub fn LLVMRustWriteTypeToString(Type: &Type, s: &RustString);
     pub fn LLVMRustWriteValueToString(value_ref: &Value, s: &RustString);

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -1098,18 +1098,6 @@ 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);