[MC][ELF] compute entity size for explicit sections

nickdesaulniers · nickdesaulniers · commit 335315697ac4 · 2018-10-10T22:52:32.000Z
Summary: Global variables might declare themselves to be in explicit sections. Calculate the entity size always to prevent assembler warnings "entity size for SHF_MERGE not specified" when sections are to be marked merge-able. Fixes PR31828. Reviewers: rnk, echristo Reviewed By: rnk Subscribers: llvm-commits, pirama, srhines Differential Revision: https://reviews.llvm.org/D53056 llvm-svn: 344197
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -506,6 +506,30 @@ static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
   return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
 }
 
+static unsigned getEntrySizeForKind(SectionKind Kind) {
+  if (Kind.isMergeable1ByteCString())
+    return 1;
+  else if (Kind.isMergeable2ByteCString())
+    return 2;
+  else if (Kind.isMergeable4ByteCString())
+    return 4;
+  else if (Kind.isMergeableConst4())
+    return 4;
+  else if (Kind.isMergeableConst8())
+    return 8;
+  else if (Kind.isMergeableConst16())
+    return 16;
+  else if (Kind.isMergeableConst32())
+    return 32;
+  else {
+    // We shouldn't have mergeable C strings or mergeable constants that we
+    // didn't handle above.
+    assert(!Kind.isMergeableCString() && "unknown string width");
+    assert(!Kind.isMergeableConst() && "unknown data width");
+    return 0;
+  }
+}
+
 MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
   StringRef SectionName = GO->getSection();
@@ -550,7 +574,7 @@ MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
 
   MCSectionELF *Section = getContext().getELFSection(
       SectionName, getELFSectionType(SectionName, Kind), Flags,
-      /*EntrySize=*/0, Group, UniqueID, AssociatedSymbol);
+      getEntrySizeForKind(Kind), Group, UniqueID, AssociatedSymbol);
   // Make sure that we did not get some other section with incompatible sh_link.
   // This should not be possible due to UniqueID code above.
   assert(Section->getAssociatedSymbol() == AssociatedSymbol &&
@@ -577,30 +601,6 @@ static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
   return ".data.rel.ro";
 }
 
-static unsigned getEntrySizeForKind(SectionKind Kind) {
-  if (Kind.isMergeable1ByteCString())
-    return 1;
-  else if (Kind.isMergeable2ByteCString())
-    return 2;
-  else if (Kind.isMergeable4ByteCString())
-    return 4;
-  else if (Kind.isMergeableConst4())
-    return 4;
-  else if (Kind.isMergeableConst8())
-    return 8;
-  else if (Kind.isMergeableConst16())
-    return 16;
-  else if (Kind.isMergeableConst32())
-    return 32;
-  else {
-    // We shouldn't have mergeable C strings or mergeable constants that we
-    // didn't handle above.
-    assert(!Kind.isMergeableCString() && "unknown string width");
-    assert(!Kind.isMergeableConst() && "unknown data width");
-    return 0;
-  }
-}
-
 static MCSectionELF *selectELFSectionForGlobal(
     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
diff --git a/llvm/test/CodeGen/Generic/section_mergeable_size.ll b/llvm/test/CodeGen/Generic/section_mergeable_size.ll
@@ -0,0 +1,3 @@
+; RUN: llc < %s | FileCheck %s
+@a = internal unnamed_addr constant [1 x [1 x i32]] zeroinitializer, section ".init.rodata", align 4
+; CHECK: .init.rodata,"aM",@progbits,4

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+; RUN: llc < %s \| FileCheck %s`
	`2`	`+@a = internal unnamed_addr constant [1 x [1 x i32]] zeroinitializer, section ".init.rodata", align 4`
	`3`	`+; CHECK: .init.rodata,"aM",@progbits,4`