[lld] [llvm] [LLD] [COFF] Add tests to observe details about LTO and __imp_ prefixes. NFC. (PR #72764)

Tue Nov 21 00:44:39 PST 2023

https://github.com/mstorsjo updated https://github.com/llvm/llvm-project/pull/72764

>From 07b2fc11b64c933211a63b8f77d719edca8a9aad Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Sun, 19 Nov 2023 12:18:49 +0200
Subject: [PATCH] [LLD] [COFF] Add tests to observe details about LTO and
 __imp_ prefixes. NFC.

The commit 3ab6209a3f93bdbeec8e9b9fcc00a9a4980915ff had the undesired
effect of retaining every __imp_ symbol, even if it isn't referenced
in any way. Add a testcase to observe this behaviour, to serve as
a reference point if this behaviour were to be improved later.

Port the testcase from b963c0b658cc54b370832df4f5a3d63fd69da334 from
the llvm/LTO testsuite into LLD as a preparation for changing that fix;
the moved testcase has a comment for one case which doesn't work
currently.

The testcase is ported mostly as is, but with symbol mangling simplified,
rewriting function names from MSVC C++ mangling to plain C, and
unnecessary debug info is removed.

Add a case of a dllimported data symbol, in addition to the existing
call of a dllimported function.

Also extend the testcase to test combinations of both regular
object files and LTO objects. Leave out one combination which currently
fails, with a comment.
---
 lld/test/COFF/lto-dllimport.ll        | 50 +++++++++++++++++++++++++++
 lld/test/COFF/lto-imp-prefix.ll       | 17 ++++++++-
 llvm/test/LTO/X86/Inputs/dllimport.ll | 17 ---------
 llvm/test/LTO/X86/dllimport.ll        | 30 ----------------
 4 files changed, 66 insertions(+), 48 deletions(-)
 create mode 100644 lld/test/COFF/lto-dllimport.ll
 delete mode 100644 llvm/test/LTO/X86/Inputs/dllimport.ll
 delete mode 100644 llvm/test/LTO/X86/dllimport.ll

diff --git a/lld/test/COFF/lto-dllimport.ll b/lld/test/COFF/lto-dllimport.ll
new file mode 100644
index 000000000000000..74f3f43d8c2810f
--- /dev/null
+++ b/lld/test/COFF/lto-dllimport.ll
@@ -0,0 +1,50 @@
+; REQUIRES: x86
+; RUN: split-file %s %t.dir
+
+; RUN: llvm-as %t.dir/main.ll -o %t.main.bc
+; RUN: llvm-as %t.dir/other.ll -o %t.other.bc
+; RUN: llc %t.dir/main.ll -o %t.main.obj --filetype=obj
+; RUN: llc %t.dir/other.ll -o %t.other.obj --filetype=obj
+
+; RUN: lld-link %t.main.obj %t.other.obj -entry:main -out:%t.exe
+; RUN: lld-link %t.main.bc  %t.other.bc  -entry:main -out:%t.exe
+; RUN: lld-link %t.main.bc  %t.other.obj -entry:main -out:%t.exe
+
+;; This test currently fails if combining the regular object file main.obj
+;; with the bitcode object file other.bc.
+; RUN-skipped: lld-link %t.main.obj %t.other.bc  -entry:main -out:%t.exe
+
+;--- main.ll
+target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.11.0"
+
+define dso_local i32 @main() local_unnamed_addr {
+entry:
+  %call = tail call i32 @foo()
+  %0 = load i32, ptr @variable, align 4
+  %add = add nsw i32 %0, %call
+  ret i32 %add
+}
+
+ at variable = external dllimport local_unnamed_addr global i32, align 4
+
+declare dllimport i32 @foo() local_unnamed_addr
+
+!llvm.module.flags = !{!1}
+
+!1 = !{i32 1, !"ThinLTO", i32 0}
+
+;--- other.ll
+target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.11.0"
+
+define dso_local i32 @foo() local_unnamed_addr {
+entry:
+  ret i32 42
+}
+
+ at variable = dso_local local_unnamed_addr global i32 1, align 4
+
+!llvm.module.flags = !{!1}
+
+!1 = !{i32 1, !"ThinLTO", i32 0}
diff --git a/lld/test/COFF/lto-imp-prefix.ll b/lld/test/COFF/lto-imp-prefix.ll
index 503e4fd0649e41d..c0b3bea7841c435 100644
--- a/lld/test/COFF/lto-imp-prefix.ll
+++ b/lld/test/COFF/lto-imp-prefix.ll
@@ -5,7 +5,15 @@
 ; RUN: llvm-as %t.dir/main.ll -o %t.main.obj
 ; RUN: llvm-as %t.dir/other.ll -o %t.other.obj
 
-; RUN: lld-link /entry:entry %t.main.obj %t.other.obj /out:%t.exe /subsystem:console
+; RUN: lld-link /entry:entry %t.main.obj %t.other.obj /out:%t.exe /subsystem:console /debug:symtab
+
+;; The current implementation for handling __imp_ symbols retains all of them.
+;; Observe that this currently produces __imp_unusedFunc even if nothing
+;; references unusedFunc in any form.
+
+; RUN: llvm-nm %t.exe | FileCheck %s
+
+; CHECK: __imp_unusedFunc
 
 ;--- main.ll
 target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
@@ -33,6 +41,13 @@ entry:
   ret void
 }
 
+ at __imp_unusedFunc = global ptr @unusedFuncReplacement
+
+define internal void @unusedFuncReplacement() {
+entry:
+  ret void
+}
+
 define void @other() {
 entry:
   ret void
diff --git a/llvm/test/LTO/X86/Inputs/dllimport.ll b/llvm/test/LTO/X86/Inputs/dllimport.ll
deleted file mode 100644
index f3daab1df09742d..000000000000000
--- a/llvm/test/LTO/X86/Inputs/dllimport.ll
+++ /dev/null
@@ -1,17 +0,0 @@
-; ModuleID = 'b.obj'
-source_filename = "b.cpp"
-target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-pc-windows-msvc19.11.0"
-
-; Function Attrs: norecurse nounwind readnone sspstrong uwtable
-define dso_local i32 @"?foo@@YAHXZ"() local_unnamed_addr {
-entry:
-  ret i32 42
-}
-
-!llvm.module.flags = !{!1}
-
-!1 = !{i32 1, !"ThinLTO", i32 0}
-
-^0 = module: (path: "b.obj", hash: (0, 0, 0, 0, 0))
-^1 = gv: (name: "?foo@@YAHXZ", summaries: (function: (module: ^0, flags: (linkage: external, notEligibleToImport: 1, live: 0, dsoLocal: 1), insts: 1, funcFlags: (readNone: 1, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0)))) ; guid = 2709792123250749187
diff --git a/llvm/test/LTO/X86/dllimport.ll b/llvm/test/LTO/X86/dllimport.ll
deleted file mode 100644
index eb9f7df5c8b30a5..000000000000000
--- a/llvm/test/LTO/X86/dllimport.ll
+++ /dev/null
@@ -1,30 +0,0 @@
-; Test requiring LTO to remove the __imp_ prefix for locally imported COFF
-; symbols (mirroring how lld handles these symbols).
-; RUN: llvm-as %s -o %t.obj
-; RUN: llvm-as %S/Inputs/dllimport.ll -o %t2.obj
-; RUN: llvm-lto2 run -r=%t.obj,main,px -r %t.obj,__imp_?foo@@YAHXZ -r %t2.obj,?foo@@YAHXZ,p -o %t3 %t.obj %t2.obj -save-temps
-; RUN: llvm-dis %t3.0.0.preopt.bc -o - | FileCheck %s
-
-; CHECK: define dso_local i32 @"?foo@@YAHXZ"()
-
-; ModuleID = 'a.obj'
-source_filename = "a.cpp"
-target datalayout = "e-m:w-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
-target triple = "x86_64-pc-windows-msvc19.11.0"
-
-; Function Attrs: norecurse nounwind sspstrong uwtable
-define dso_local i32 @main() local_unnamed_addr {
-entry:
-  %call = tail call i32 @"?foo@@YAHXZ"()
-  ret i32 %call
-}
-
-declare dllimport i32 @"?foo@@YAHXZ"() local_unnamed_addr
-
-!llvm.module.flags = !{!1}
-
-!1 = !{i32 1, !"ThinLTO", i32 0}
-
-^0 = module: (path: "a.obj", hash: (0, 0, 0, 0, 0))
-^1 = gv: (name: "?foo@@YAHXZ") ; guid = 2709792123250749187
-^2 = gv: (name: "main", summaries: (function: (module: ^0, flags: (linkage: external, notEligibleToImport: 1, live: 0, dsoLocal: 1), insts: 2, funcFlags: (readNone: 0, readOnly: 0, noRecurse: 1, returnDoesNotAlias: 0), calls: ((callee: ^1))))) ; guid = 15822663052811949562

