[lld][ELF][test] Add additional --symbol-ordering-file testing

This covers a few cases that aren't otherwise tested:
1) Non-ascii symbol names are ordered.
2) Comments, whitespace and blank lines are trimmed.
3) Missing order files result in an error.

Reviewed by: MaskRay, grimar

Differential Revision: https://reviews.llvm.org/D90933

lld/test/ELF/symbol-ordering-file.s

@@ -4,31 +4,53 @@
 # RUN: llvm-objdump -s %t.out| FileCheck %s --check-prefix=BEFORE
 
 # BEFORE:      Contents of section .foo:
-# BEFORE-NEXT:  11223344 5566
+# BEFORE-NEXT:  11223344 556677
 # BEFORE:      Contents of section .init:
 # BEFORE-NEXT:  1122
 
 # RUN: echo "_foo4  " > %t_order.txt
 # RUN: echo "  _foo3" >> %t_order.txt
+# RUN: echo "_nönascii" >> %t_order.txt
 # RUN: echo "_foo5" >> %t_order.txt
-# RUN: echo "_foo2" >> %t_order.txt
+# RUN: echo -e " _foo2 \t\v\r\f" >> %t_order.txt
+# RUN: echo "# a comment" >> %t_order.txt
 # RUN: echo " " >> %t_order.txt
 # RUN: echo "_foo4" >> %t_order.txt
 # RUN: echo "_bar1" >> %t_order.txt
+# RUN: echo "" >> %t_order.txt
 # RUN: echo "_foo1" >> %t_order.txt
 # RUN: echo "_init2" >> %t_order.txt
 # RUN: echo "_init1" >> %t_order.txt
 
-# RUN: ld.lld --symbol-ordering-file %t_order.txt %t.o -o %t2.out
+## Show that both --symbol-ordering-file and --symbol-ordering-file= work.
+## Also show that lines beginning with '#', whitespace and empty lines, are ignored.
+## Also show that "first one wins" when there are duplicate symbols in the order
+## file (a warning will be emitted).
+# RUN: ld.lld --symbol-ordering-file %t_order.txt %t.o -o %t2.out 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=WARN --implicit-check-not=warning:
 # RUN: llvm-objdump -s %t2.out | FileCheck %s --check-prefix=AFTER
 # RUN: ld.lld --symbol-ordering-file=%t_order.txt %t.o -o %t2.out
 # RUN: llvm-objdump -s %t2.out | FileCheck %s --check-prefix=AFTER
 
+# WARN: warning: {{.*}}.txt: duplicate ordered symbol
+
 # AFTER:      Contents of section .foo:
-# AFTER-NEXT:  44335566 2211
+# AFTER-NEXT:  44337755 662211
 # AFTER:      Contents of section .init:
 # AFTER-NEXT:  1122
 
+## Show that a nonexistent symbol ordering file causes an error.
+# RUN: not ld.lld --symbol-ordering-file=%t.nonexistent %t.o -o %t3.out 2>&1 | \
+# RUN:   FileCheck %s --check-prefix=ERR -DFILE=%t.nonexistent
+
+# ERR: error: cannot open [[FILE]]: {{[Nn]}}o such file or directory
+
+## Show that an empty ordering file can be handled (symbols remain in their
+## normal order).
+# RUN: touch %t.empty
+# RUN: ld.lld --symbol-ordering-file=%t.empty %t.o -o %t4.out
+# RUN: llvm-objdump -s %t4.out | FileCheck %s --check-prefix=BEFORE
+
 .section .foo,"ax",@progbits,unique,1
 _foo1:
  .byte 0x11
@@ -51,6 +73,10 @@ _foo5:
 _bar1:
  .byte 0x66
 
+.section .foo,"ax",@progbits,unique,6
+"_nönascii":
+.byte 0x77
+
 .section .init,"ax",@progbits,unique,1
 _init1:
  .byte 0x11
@@ -58,3 +84,8 @@ _init1:
 .section .init,"ax",@progbits,unique,2
 _init2:
  .byte 0x22
+
+.text
+.global _start
+_start:
+    nop