Revert "[X86] Don't respect large data threshold for globals with an explicit section (llvm#78348)"

This reverts commit 00647a1.

Author: Zentrik

llvm/lib/Target/TargetMachine.cpp

@@ -58,29 +58,31 @@ bool TargetMachine::isLargeGlobalValue(const GlobalValue *GVal) const {
   if (GV->isThreadLocal())
     return false;
 
+  // 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();
+  if (!Name.empty()) {
+    auto IsPrefix = [&](StringRef Prefix) {
+      StringRef S = Name;
+      return S.consume_front(Prefix) && (S.empty() || S[0] == '.');
+    };
+    if (IsPrefix(".bss") || IsPrefix(".data") || IsPrefix(".rodata"))
+      return false;
+    if (IsPrefix(".lbss") || IsPrefix(".ldata") || IsPrefix(".lrodata"))
+      return true;
+  }
+
   // For x86-64, we treat an explicit GlobalVariable small code model to mean
   // that the global should be placed in a small section, and ditto for large.
+  // Well-known section names above take precedence for correctness.
   if (auto CM = GV->getCodeModel()) {
     if (*CM == CodeModel::Small)
       return false;
     if (*CM == CodeModel::Large)
       return true;
   }
 
-  // Treat all globals in explicit sections as small, except for the standard
-  // large sections of .lbss, .ldata, .lrodata. This reduces the risk of linking
-  // together small and large sections, resulting in small references to large
-  // data sections. The code model attribute overrides this above.
-  if (GV->hasSection()) {
-    StringRef Name = GV->getSection();
-    auto IsPrefix = [&](StringRef Prefix) {
-      StringRef S = Name;
-      return S.consume_front(Prefix) && (S.empty() || S[0] == '.');
-    };
-    return IsPrefix(".lbss") || IsPrefix(".ldata") || IsPrefix(".lrodata");
-  }
-
-  // Respect large data threshold for medium and large code models.
   if (getCodeModel() == CodeModel::Medium ||
       getCodeModel() == CodeModel::Large) {
     if (!GV->getValueType()->isSized())

llvm/test/CodeGen/X86/code-model-elf-sections.ll

@@ -55,13 +55,13 @@
 
 ; LARGE: .data {{.*}} WA {{.*}}
 ; LARGE: .data.x {{.*}} WA {{.*}}
-; LARGE: .data0 {{.*}} WA {{.*}}
+; LARGE: .data0 {{.*}} WAl {{.*}}
 ; LARGE: .ldata {{.*}} WAl {{.*}}
 ; LARGE: .ldata.x {{.*}} WAl {{.*}}
-; LARGE: .ldata0 {{.*}} WA {{.*}}
+; LARGE: .ldata0 {{.*}} WAl {{.*}}
 ; LARGE: force_small {{.*}} WA {{.*}}
 ; LARGE: force_large {{.*}} WAl {{.*}}
-; LARGE: foo {{.*}} WA {{.*}}
+; LARGE: foo {{.*}} WAl {{.*}}
 ; LARGE: .bss {{.*}} WA {{.*}}
 ; LARGE: .lbss {{.*}} WAl {{.*}}
 ; LARGE: .rodata {{.*}} A {{.*}}
@@ -72,14 +72,14 @@
 
 ; LARGE-DS: .data {{.*}} WA {{.*}}
 ; LARGE-DS: .data.x {{.*}} WA {{.*}}
-; LARGE-DS: .data0 {{.*}} WA {{.*}}
+; LARGE-DS: .data0 {{.*}} WAl {{.*}}
 ; LARGE-DS: .ldata {{.*}} WAl {{.*}}
 ; LARGE-DS: .ldata.x {{.*}} WAl {{.*}}
-; LARGE-DS: .ldata0 {{.*}} WA {{.*}}
+; LARGE-DS: .ldata0 {{.*}} WAl {{.*}}
 ; LARGE-DS: .ldata.data {{.*}} WAl {{.*}}
 ; LARGE-DS: force_small {{.*}} WA {{.*}}
 ; LARGE-DS: force_large {{.*}} WAl {{.*}}
-; LARGE-DS: foo {{.*}} WA {{.*}}
+; LARGE-DS: foo {{.*}} WAl {{.*}}
 ; LARGE-DS: .bss {{.*}} WA {{.*}}
 ; LARGE-DS: .lbss.bss {{.*}} WAl {{.*}}
 ; LARGE-DS: .rodata {{.*}} A {{.*}}