[lld] bc20bcb - [lld/mac] Crash even less on undefined symbols with --icf=all

[Nico Weber via llvm-commits]

Author: Nico Weber
Date: 2021-11-19T09:23:19-05:00
New Revision: bc20bcb39e02e7b593fe0f50fe47959b635f5e56

URL: https://github.com/llvm/llvm-project/commit/bc20bcb39e02e7b593fe0f50fe47959b635f5e56
DIFF: https://github.com/llvm/llvm-project/commit/bc20bcb39e02e7b593fe0f50fe47959b635f5e56.diff

LOG: [lld/mac] Crash even less on undefined symbols with --icf=all

Follow-up to https://reviews.llvm.org/D112643. Even after that change, we were
still asserting if two separate functions that are eligible for ICF (same size,
same data, same number of relocs, same reloc types, ...) referred to
Undefineds. This fixes that oversight.

Differential Revision: https://reviews.llvm.org/D114195

Added: 
    

Modified: 
    lld/MachO/ICF.cpp
    lld/test/MachO/invalid/undefined-symbol.s

Removed: 
    


################################################################################
diff  --git a/lld/MachO/ICF.cpp b/lld/MachO/ICF.cpp
index 8802f292a9c85..f9dea4b861ac3 100644
--- a/lld/MachO/ICF.cpp
+++ b/lld/MachO/ICF.cpp
@@ -114,7 +114,8 @@ static bool equalsConstant(const ConcatInputSection *ia,
       if (sa->kind() != sb->kind())
         return false;
       if (!isa<Defined>(sa)) {
-        assert(isa<DylibSymbol>(sa));
+        // ICF runs before Undefineds are reported.
+        assert(isa<DylibSymbol>(sa) || isa<Undefined>(sa));
         return sa == sb;
       }
       const auto *da = cast<Defined>(sa);
@@ -275,7 +276,7 @@ void ICF::run() {
             } else {
               hash += defined->value;
             }
-          } else if (!isa<Undefined>(sym))
+          } else if (!isa<Undefined>(sym)) // ICF runs before Undefined diags.
             llvm_unreachable("foldIdenticalSections symbol kind");
         }
       }

diff  --git a/lld/test/MachO/invalid/undefined-symbol.s b/lld/test/MachO/invalid/undefined-symbol.s
index deb543a31462f..97a300494b277 100644
--- a/lld/test/MachO/invalid/undefined-symbol.s
+++ b/lld/test/MachO/invalid/undefined-symbol.s
@@ -20,9 +20,17 @@ _foo:
   retq
 
 #--- main.s
-.globl _main
 .text
+
+_anotherref:
+  callq _foo
+  movq $0, %rax
+  retq
+
+.globl _main
 _main:
   callq _foo
   movq $0, %rax
   retq
+
+.subsections_via_symbols