[ELF] BitcodeFile: resolve defined symbols before undefined symbols

This ports D95985 for ELF relocatable object files to BitcodeFile.

Author: MaskRay

lld/ELF/InputFiles.cpp

@@ -1666,10 +1666,18 @@ template <class ELFT> void BitcodeFile::parse() {
   }
 
   symbols.resize(obj->symbols().size());
-  for (auto it : llvm::enumerate(obj->symbols())) {
-    Symbol *&sym = symbols[it.index()];
-    createBitcodeSymbol<ELFT>(sym, keptComdats, it.value(), *this);
-  }
+  // Process defined symbols first. See the comment in
+  // ObjFile<ELFT>::initializeSymbols.
+  for (auto it : llvm::enumerate(obj->symbols()))
+    if (!it.value().isUndefined()) {
+      Symbol *&sym = symbols[it.index()];
+      createBitcodeSymbol<ELFT>(sym, keptComdats, it.value(), *this);
+    }
+  for (auto it : llvm::enumerate(obj->symbols()))
+    if (it.value().isUndefined()) {
+      Symbol *&sym = symbols[it.index()];
+      createBitcodeSymbol<ELFT>(sym, keptComdats, it.value(), *this);
+    }
 
   for (auto l : obj->getDependentLibraries())
     addDependentLibrary(l, this);

lld/test/ELF/lto/comdat-mixed-archive.test

@@ -29,10 +29,10 @@ BCSYM-NEXT: W foo
 ;; Check that the symbols are handled in the expected order.
 TRACE:      lib.a(obj.o): lazy definition of foo
 TRACE-NEXT: lib.a(obj.o): lazy definition of bar
+TRACE-NEXT: lib.a(bc.bc): definition of foo
 TRACE-NEXT: lib.a(bc.bc): reference to bar
 TRACE-NEXT: lib.a(obj.o): reference to foo
 TRACE-NEXT: lib.a(obj.o): definition of bar
-TRACE-NEXT: lib.a(bc.bc): definition of foo
 TRACE-NEXT: <internal>: reference to foo
 ;; The definition of "foo" is visible outside the LTO result.
 TRACE-NEXT: lto.tmp: definition of foo

lld/test/ELF/lto/start-lib.ll

@@ -6,18 +6,18 @@
 ;
 ; RUN: ld.lld -shared -o %t3 %t1.o %t2.o %t3.o
 ; RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=TEST1 %s
-; TEST1: Name: bar
 ; TEST1: Name: foo
+; TEST1: Name: bar
 ;
 ; RUN: ld.lld -shared -o %t3 -u bar %t1.o --start-lib %t2.o %t3.o
 ; RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=TEST2 %s
-; TEST2: Name: bar
 ; TEST2-NOT: Name: foo
+; TEST2: Name: bar
 ;
 ; RUN: ld.lld -shared -o %t3 %t1.o --start-lib %t2.o %t3.o
 ; RUN: llvm-readobj --symbols %t3 | FileCheck --check-prefix=TEST3 %s
-; TEST3-NOT: Name: bar
 ; TEST3-NOT: Name: foo
+; TEST3-NOT: Name: bar
 
 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"

lld/test/ELF/lto/visibility.ll

@@ -5,25 +5,25 @@
 ; RUN: llvm-dis < %t.so.0.2.internalize.bc | FileCheck --check-prefix=IR %s
 ; RUN: llvm-readobj --symbols %t.so | FileCheck %s
 
-; CHECK:      Name: g
+; CHECK:      Name: a
 ; CHECK-NEXT: Value:
 ; CHECK-NEXT: Size: 0
 ; CHECK-NEXT: Binding: Local
 ; CHECK-NEXT: Type: None
 ; CHECK-NEXT: Other [ (0x2)
 ; CHECK-NEXT:   STV_HIDDEN
 ; CHECK-NEXT: ]
-; CHECK-NEXT: Section: .text
+; CHECK-NEXT: Section: .data
 
-; CHECK:      Name: a
+; CHECK:      Name: g
 ; CHECK-NEXT: Value:
 ; CHECK-NEXT: Size: 0
 ; CHECK-NEXT: Binding: Local
 ; CHECK-NEXT: Type: None
 ; CHECK-NEXT: Other [ (0x2)
 ; CHECK-NEXT:   STV_HIDDEN
 ; CHECK-NEXT: ]
-; CHECK-NEXT: Section: .data
+; CHECK-NEXT: Section: .text
 
 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"