Add support for #pragma clang section

This patch provides a means to specify section-names for global variables,
functions and static variables, using #pragma directives.
This feature is only defined to work sensibly for ELF targets.
One can specify section names as:
#pragma clang section bss="myBSS" data="myData" rodata="myRodata" text="myText"
One can "unspecify" a section name with empty string e.g.
#pragma clang section bss="" data="" text="" rodata=""

Reviewers: Roger Ferrer, Jonathan Roelofs, Reid Kleckner
Differential Revision: https://reviews.llvm.org/D33413

llvm-svn: 304704

1 files changed, 14 insertions, 0 deletions

diff --git a/llvm/lib/Target/TargetLoweringObjectFile.cpp b/llvm/lib/Target/TargetLoweringObjectFile.cpp
index 91cc97e38b3..293a62007af 100644
--- a/llvm/lib/Target/TargetLoweringObjectFile.cpp
+++ b/llvm/lib/Target/TargetLoweringObjectFile.cpp
@@ -240,6 +240,20 @@ MCSection *TargetLoweringObjectFile::SectionForGlobal(
   if (GO->hasSection())
     return getExplicitSectionGlobal(GO, Kind, TM);
 
+  if (auto *GVar = dyn_cast<GlobalVariable>(GO)) {
+    auto Attrs = GVar->getAttributes();
+    if ((Attrs.hasAttribute("bss-section") && Kind.isBSS()) ||
+        (Attrs.hasAttribute("data-section") && Kind.isData()) ||
+        (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()))  {
+       return getExplicitSectionGlobal(GO, Kind, TM);
+    }
+  }
+
+  if (auto *F = dyn_cast<Function>(GO)) {
+    if (F->hasFnAttribute("implicit-section-name"))
+      return getExplicitSectionGlobal(GO, Kind, TM);
+  }
+
   // Use default section depending on the 'type' of global
   return SelectSectionForGlobal(GO, Kind, TM);
 }