[X86] Set SHF_X86_64_LARGE for globals with explicit well-known large section name

[aeubanks]

Globals marked with the .lbss/.ldata/.lrodata should automatically be treated as large.
Do this regardless of the code model for consistency when mixing object files compiled with different code models.

Basically the other half of #70748.

Example in the wild:
https://codebrowser.dev/qt5/qtbase/src/testlib/qtestcase.cpp.html#1664

[llvmbot]

@llvm/pr-subscribers-backend-x86

Author: Arthur Eubanks (aeubanks)

Changes

Globals marked with the .lbss/.ldata/.lrodata should automatically be treated as large.
Do this regardless of the code model for consistency when mixing object files compiled with different code models.

Basically the opposite of #70748.

Example in the wild:
https://codebrowser.dev/qt5/qtbase/src/testlib/qtestcase.cpp.html#1664

---

Full diff: https://github.com/llvm/llvm-project/pull/74381.diff

2 Files Affected:

• (modified) llvm/lib/Target/TargetMachine.cpp (+9-7)
• (modified) llvm/test/CodeGen/X86/code-model-elf-sections.ll (+20)

diff --git a/llvm/lib/Target/TargetMachine.cpp b/llvm/lib/Target/TargetMachine.cpp
index f7096b708b39d..58a785434f659 100644
--- a/llvm/lib/Target/TargetMachine.cpp
+++ b/llvm/lib/Target/TargetMachine.cpp
@@ -43,9 +43,6 @@ bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
   if (getTargetTriple().getArch() != Triple::x86_64)
     return false;
 
-  if (getCodeModel() != CodeModel::Medium && getCodeModel() != CodeModel::Large)
-    return false;
-
   if (isa<Function>(GO))
     return getCodeModel() == CodeModel::Large;
 
@@ -55,10 +52,10 @@ bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
     return false;
 
   // Allowing large metadata sections in the presence of an explicit section is
-  // useful, even if GCC does not allow them. However, we should not mark
-  // certain well-known prefixes as large, because it would make the whole
-  // output section large and cause the linker to move it, which is almost
-  // always undesired.
+  // useful, even if GCC does not allow them. However, we should properly mark
+  // well-known section name prefixes as small/large, because otherwise the
+  // output section may have the wrong section flags and the linker will lay it
+  // out in an unexpected way.
   StringRef Name = GV->getSection();
   auto IsPrefix = [&](StringRef Prefix) {
     StringRef S = Name;
@@ -66,6 +63,11 @@ bool TargetMachine::isLargeGlobalObject(const GlobalObject *GO) const {
   };
   if (IsPrefix(".bss") || IsPrefix(".data") || IsPrefix(".rodata"))
     return false;
+  if (IsPrefix(".lbss") || IsPrefix(".ldata") || IsPrefix(".lrodata"))
+    return true;
+
+  if (getCodeModel() != CodeModel::Medium && getCodeModel() != CodeModel::Large)
+    return false;
 
   const DataLayout &DL = GV->getParent()->getDataLayout();
   uint64_t Size = DL.getTypeSizeInBits(GV->getValueType()) / 8;
diff --git a/llvm/test/CodeGen/X86/code-model-elf-sections.ll b/llvm/test/CodeGen/X86/code-model-elf-sections.ll
index 0b99a70c4044a..f72880e172bdc 100644
--- a/llvm/test/CodeGen/X86/code-model-elf-sections.ll
+++ b/llvm/test/CodeGen/X86/code-model-elf-sections.ll
@@ -21,9 +21,14 @@
 ; SMALL: .data {{.*}} WA {{.*}}
 ; SMALL: .data.x {{.*}} WA {{.*}}
 ; SMALL: .data0 {{.*}} WA {{.*}}
+; SMALL: .ldata {{.*}} WAl {{.*}}
+; SMALL: .ldata.x {{.*}} WAl {{.*}}
+; SMALL: .ldata0 {{.*}} WA {{.*}}
 ; SMALL: foo {{.*}} WA {{.*}}
 ; SMALL: .bss {{.*}} WA {{.*}}
+; SMALL: .lbss {{.*}} WAl {{.*}}
 ; SMALL: .rodata {{.*}} A {{.*}}
+; SMALL: .lrodata {{.*}} Al {{.*}}
 ; SMALL: .data.rel.ro {{.*}} WA {{.*}}
 ; SMALL: .tbss {{.*}} WAT {{.*}}
 ; SMALL: .tdata {{.*}} WAT {{.*}}
@@ -31,9 +36,14 @@
 ; SMALL-DS: .data {{.*}} WA {{.*}}
 ; SMALL-DS: .data.x {{.*}} WA {{.*}}
 ; SMALL-DS: .data0 {{.*}} WA {{.*}}
+; SMALL-DS: .ldata {{.*}} WAl {{.*}}
+; SMALL-DS: .ldata.x {{.*}} WAl {{.*}}
+; SMALL-DS: .ldata0 {{.*}} WA {{.*}}
 ; SMALL-DS: .data.data {{.*}} WA {{.*}}
 ; SMALL-DS: foo {{.*}} WA {{.*}}
+; SMALL-DS: .lbss {{.*}} WAl {{.*}}
 ; SMALL-DS: .bss.bss {{.*}} WA {{.*}}
+; SMALL-DS: .lrodata {{.*}} Al {{.*}}
 ; SMALL-DS: .rodata.rodata {{.*}} A {{.*}}
 ; SMALL-DS: .data.rel.ro.relro {{.*}} WA {{.*}}
 ; SMALL-DS: .tbss.tbss {{.*}} WAT {{.*}}
@@ -43,6 +53,8 @@
 ; LARGE: .data.x {{.*}} WA {{.*}}
 ; LARGE: .data0 {{.*}} WAl {{.*}}
 ; LARGE: .ldata {{.*}} WAl {{.*}}
+; LARGE: .ldata.x {{.*}} WAl {{.*}}
+; LARGE: .ldata0 {{.*}} WAl {{.*}}
 ; LARGE: foo {{.*}} WAl {{.*}}
 ; LARGE: .bss {{.*}} WA {{.*}}
 ; LARGE: .lbss {{.*}} WAl {{.*}}
@@ -55,6 +67,9 @@
 ; LARGE-DS: .data {{.*}} WA {{.*}}
 ; LARGE-DS: .data.x {{.*}} WA {{.*}}
 ; LARGE-DS: .data0 {{.*}} WAl {{.*}}
+; LARGE-DS: .ldata {{.*}} WAl {{.*}}
+; LARGE-DS: .ldata.x {{.*}} WAl {{.*}}
+; LARGE-DS: .ldata0 {{.*}} WAl {{.*}}
 ; LARGE-DS: .ldata.data {{.*}} WAl {{.*}}
 ; LARGE-DS: foo {{.*}} WAl {{.*}}
 ; LARGE-DS: .bss {{.*}} WA {{.*}}
@@ -71,11 +86,16 @@ target triple = "x86_64--linux"
 @data_with_explicit_section = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".data"
 @data_with_explicit_section2 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".data.x"
 @data_with_explicit_section0 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".data0"
+@ldata_with_explicit_section = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".ldata"
+@ldata_with_explicit_section2 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".ldata.x"
+@ldata_with_explicit_section0 = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section ".ldata0"
 @data = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0]
 @foo_with_explicit_section = internal global [10 x i64] [i64 1, i64 2, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0, i64 0], section "foo"
 @bss_with_explicit_section = internal global [10 x i64] zeroinitializer, section ".bss"
+@lbss_with_explicit_section = internal global [10 x i64] zeroinitializer, section ".lbss"
 @bss = internal global [10 x i64] zeroinitializer
 @rodata_with_explicit_section = internal constant [10 x i64] zeroinitializer, section ".rodata"
+@lrodata_with_explicit_section = internal constant [10 x i64] zeroinitializer, section ".lrodata"
 @rodata = internal constant [10 x i64] zeroinitializer
 @relro = internal constant [10 x ptr] [ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func, ptr @func]
 @tbss = internal thread_local global [10 x i64] zeroinitializer