[lld] 912e821 - [LLD][COFF] Process all live import symbols in MapFile's getSymbols() (#109117)

[via llvm-commits]

Author: Jacek Caban
Date: 2024-09-19T13:20:01+02:00
New Revision: 912e821ab3d415dc8421f53738ebabcc7f1dac2d

URL: https://github.com/llvm/llvm-project/commit/912e821ab3d415dc8421f53738ebabcc7f1dac2d
DIFF: https://github.com/llvm/llvm-project/commit/912e821ab3d415dc8421f53738ebabcc7f1dac2d.diff

LOG: [LLD][COFF] Process all live import symbols in MapFile's getSymbols() (#109117)

The current logic assumes that the import file is pulled by object
files, and the loop for import files only needs to handle cases where
the `__imp_` symbol is implicitly pulled by an import thunk. This is
fragile, as the symbol may also be pulled through other means, such as
the -export argument in tests. Additionally, this logic is insufficient
for ARM64EC, which exposes multiple symbols through an import file, and
referencing any one of them causes all of them to be defined.
    
With this change, import symbols are added to `syms` more often, but we
ensure that output symbols remain unique later in the process

Added: 
    lld/test/COFF/export-imp.test

Modified: 
    lld/COFF/MapFile.cpp

Removed: 
    


################################################################################
diff  --git a/lld/COFF/MapFile.cpp b/lld/COFF/MapFile.cpp
index 751a2238e701f7..7c9c1711214550 100644
--- a/lld/COFF/MapFile.cpp
+++ b/lld/COFF/MapFile.cpp
@@ -122,16 +122,10 @@ static void getSymbols(const COFFLinkerContext &ctx,
     if (!file->live)
       continue;
 
-    if (!file->thunkSym)
-      continue;
-
-    if (!file->thunkSym->isLive())
-      continue;
-
-    syms.push_back(file->thunkSym);
-
-    if (auto *impSym = dyn_cast_or_null<Defined>(file->impSym))
-      syms.push_back(impSym);
+    if (file->impSym)
+      syms.push_back(file->impSym);
+    if (file->thunkSym && file->thunkSym->isLive())
+      syms.push_back(file->thunkSym);
   }
 
   sortUniqueSymbols(syms, ctx.config.imageBase);

diff  --git a/lld/test/COFF/export-imp.test b/lld/test/COFF/export-imp.test
new file mode 100644
index 00000000000000..db71ef74641639
--- /dev/null
+++ b/lld/test/COFF/export-imp.test
@@ -0,0 +1,11 @@
+; REQUIRES: x86
+
+; RUN: llvm-lib -machine:amd64 -out:%t.imp.lib -def:%s
+; RUN: lld-link -machine:amd64 -out:%t.dll %t.imp.lib -dll -noentry -export:__imp_func,DATA -map
+
+; FileCheck %s < %t.imp.map
+; CHECK: 0001:00000098       __imp_func                 0000000180001098     export-imp-thunk.test.tmp.imp:imp.dll
+
+LIBRARY imp.dll
+EXPORTS
+        func