Fixed placement of llvm.global_dtors on Windows.

[vzakhari]

Summary

This fixes a regression after the following commit:
commit f803b23879d9e1d9415ec1875713534dcc203df5
Author: Reid Kleckner <[e-mail]>
Date: Fri Sep 7 23:07:55 2018 +0000

[COFF] Implement llvm.global_ctors priorities for MSVC COFF targets

[rnk]

lgtm, thanks!

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
     // Otherwise, we need to compute a new section name. Low priorities should
     // run earlier. The linker will sort sections ASCII-betically, and we need a
     // string that sorts between .CRT$XCA and .CRT$XCU. In the general case, we
     // make a name like ".CRT$XCT12345", since that runs before .CRT$XCU. Really
     // low priorities need to sort before 'L', since the CRT uses that
     // internally, so we use ".CRT$XCA00001" for them.
     SmallString<24> Name;
     raw_svector_ostream OS(Name);
-    OS << ".CRT$XC" << (Priority < 200 ? 'A' : 'T') << format("%05u", Priority);
+    OS << ".CRT$X" << (IsCtor ? "C" : "T") <<
+        (Priority < 200 ? 'A' : 'T') << format("%05u", Priority);
     MCSectionCOFF *Sec = Ctx.getCOFFSection(
         Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
         SectionKind::getReadOnly());
     return Ctx.getAssociativeCOFFSection(Sec, KeySym, 0);
   }
 
   std::string Name = IsCtor ? ".ctors" : ".dtors";
   if (Priority != 65535)

llvm/test/CodeGen/X86/dtor-priority-coff.ll

+; RUN: llc < %s | FileCheck %s
+
+; Check that we come up with appropriate section names that link.exe sorts
+; well.
+
+; CHECK: .section        .CRT$XTA00042,"dr"
+; CHECK: .p2align        3
+; CHECK: .quad   f
+; CHECK: .section        .CRT$XTT12345,"dr"
+; CHECK: .p2align        3
+; CHECK: .quad   g
+; CHECK: .section        .CRT$XTT23456,"dr",associative,h
+; CHECK: .p2align        3
+; CHECK: .quad   init_h
+; CHECK: .section        .CRT$XTX,"dr"
+; CHECK: .p2align        3
+; CHECK: .quad   str3_dtor
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.14.26433"
+
+$h = comdat any
+
+@h = linkonce_odr global i8 55, comdat, align 1
+
+@str0 = private dso_local unnamed_addr constant [6 x i8] c"later\00", align 1
+@str1 = private dso_local unnamed_addr constant [6 x i8] c"first\00", align 1
+@str2 = private dso_local unnamed_addr constant [5 x i8] c"main\00", align 1
+@str3 = private dso_local unnamed_addr constant [8 x i8] c"default\00", align 1
+
[e-mail]_dtors = appending global [4 x { i32, void ()*, i8* }] [
+  { i32, void ()*, i8* } { i32 12345, void ()* @g, i8* null },
+  { i32, void ()*, i8* } { i32 42, void ()* @f, i8* null },
+  { i32, void ()*, i8* } { i32 23456, void ()* @init_h, i8* @h },
+  { i32, void ()*, i8* } { i32 65535, void ()* @str3_dtor, i8* null }
+]
+
+declare dso_local i32 @puts(i8* nocapture readonly) local_unnamed_addr
+
+define dso_local void @g() {
+entry:
+  %call = tail call i32 @puts(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @str0, i64 0, i64 0))
+  ret void
+}
+
+define dso_local void @f() {
+entry:
+  %call = tail call i32 @puts(i8* getelementptr inbounds ([6 x i8], [6 x i8]* @str1, i64 0, i64 0))
+  ret void
+}
+
+define dso_local void @str3_dtor() {
+entry:
+  %call = tail call i32 @puts(i8* getelementptr inbounds ([8 x i8], [8 x i8]* @str3, i64 0, i64 0))
+  ret void
+}
+
+define dso_local void @init_h() {
+entry:
+  store i8 42, i8* @h
+  ret void
+}
+
+
+; Function Attrs: nounwind uwtable
+define dso_local i32 @main() local_unnamed_addr {
+entry:
+  %call = tail call i32 @puts(i8* getelementptr inbounds ([5 x i8], [5 x i8]* @str2, i64 0, i64 0))
+  ret i32 0
+}