[llvm] [CodeGen] Sort .ctors in reverse on MinGW just like on other platforms (PR #68570)

[Martin Storsjö via llvm-commits]

https://github.com/mstorsjo created https://github.com/llvm/llvm-project/pull/68570

On MinGW targets, the .ctors section is always used (as opposed to on ELF platforms, where .init_section is the default but one can select using .ctors, with the -use-ctors option, or the UseInitArray field in TargetOptions).

Apply the reverse ordering regardless of whether the caller has set the UseInitArray flag for this target, as this target unconditionally uses the .ctors section anyway.

For the CodeGen/X86/constructor.ll testcase, note how this now produces the same output ordering as for ELF targets with -use-ctors.

This fixes https://github.com/llvm/llvm-project/issues/55938.

>From 24dd10c6483d0246464277ecc0e89aaeb561ec88 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Martin=20Storsj=C3=B6?= <martin at martin.st>
Date: Mon, 9 Oct 2023 13:08:39 +0300
Subject: [PATCH] [CodeGen] Sort .ctors in reverse on MinGW just like on other
 platforms

On MinGW targets, the .ctors section is always used (as opposed
to on ELF platforms, where .init_section is the default but
one can select using .ctors, with the -use-ctors option, or the
UseInitArray field in TargetOptions).

Apply the reverse ordering regardless of whether the caller has
set the UseInitArray flag for this target, as this target
unconditionally uses the .ctors section anyway.

For the CodeGen/X86/constructor.ll testcase, note how this now
produces the same output ordering as for ELF targets with -use-ctors.

This fixes https://github.com/llvm/llvm-project/issues/55938.
---
 llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp |  6 +++++-
 llvm/test/CodeGen/X86/constructor.ll       | 12 ++++++------
 llvm/test/MC/COFF/global_ctors_dtors.ll    |  4 ++--
 3 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index 97d2fe3426406f3..5f4141e17541bf7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -2807,7 +2807,11 @@ void AsmPrinter::emitXXStructorList(const DataLayout &DL, const Constant *List,
 
   // Emit the structors in reverse order if we are using the .ctor/.dtor
   // initialization scheme.
-  if (!TM.Options.UseInitArray)
+  bool UseCtorSection = !TM.Options.UseInitArray;
+  // MinGW targets always use the .ctors section.
+  if (TM.getTargetTriple().isWindowsGNUEnvironment())
+    UseCtorSection = true;
+  if (UseCtorSection)
     std::reverse(Structors.begin(), Structors.end());
 
   const Align Align = DL.getPointerPrefAlignment();
diff --git a/llvm/test/CodeGen/X86/constructor.ll b/llvm/test/CodeGen/X86/constructor.ll
index 0fea69b5a7bcb52..4bc4e72b6472a68 100644
--- a/llvm/test/CodeGen/X86/constructor.ll
+++ b/llvm/test/CodeGen/X86/constructor.ll
@@ -77,14 +77,14 @@ entry:
 ; MCU-CTORS:         .section        .ctors,"aw", at progbits
 ; MCU-INIT-ARRAY:    .section        .init_array,"aw", at init_array
 
-; COFF-CTOR:		.section	.ctors.65520,"dw",associative,v
+; COFF-CTOR:		.section	.ctors,"dw"
 ; COFF-CTOR-NEXT:	.p2align	3
-; COFF-CTOR-NEXT:	.quad	g
+; COFF-CTOR-NEXT:	.quad	j
+; COFF-CTOR-NEXT:	.quad	i
+; COFF-CTOR-NEXT:	.quad	f
 ; COFF-CTOR-NEXT:	.section	.ctors.09980,"dw",associative,v
 ; COFF-CTOR-NEXT:	.p2align	3
 ; COFF-CTOR-NEXT:	.quad	h
-; COFF-CTOR-NEXT:	.section	.ctors,"dw"
+; COFF-CTOR-NEXT:	.section	.ctors.65520,"dw",associative,v
 ; COFF-CTOR-NEXT:	.p2align	3
-; COFF-CTOR-NEXT:	.quad	f
-; COFF-CTOR-NEXT:	.quad	i
-; COFF-CTOR-NEXT:	.quad	j
+; COFF-CTOR-NEXT:	.quad	g
diff --git a/llvm/test/MC/COFF/global_ctors_dtors.ll b/llvm/test/MC/COFF/global_ctors_dtors.ll
index 7df4d3e500b54c3..9b321a082a32e58 100644
--- a/llvm/test/MC/COFF/global_ctors_dtors.ll
+++ b/llvm/test/MC/COFF/global_ctors_dtors.ll
@@ -56,10 +56,10 @@ define i32 @main() nounwind {
 ; WIN32-NOT: c_global_ctor
 ; WIN32: .section .CRT$XTX,"dr"
 ; WIN32: a_global_dtor
-; MINGW32: .section .ctors,"dw"
-; MINGW32: a_global_ctor
 ; MINGW32: .section .ctors,"dw",associative,{{_?}}b
 ; MINGW32: b_global_ctor
 ; MINGW32-NOT: c_global_ctor
+; MINGW32: .section .ctors,"dw"
+; MINGW32: a_global_ctor
 ; MINGW32: .section .dtors,"dw"
 ; MINGW32: a_global_dtor