Index: llvm/lib/Target/TargetLoweringObjectFile.cpp
===================================================================
--- llvm/lib/Target/TargetLoweringObjectFile.cpp
+++ llvm/lib/Target/TargetLoweringObjectFile.cpp
@@ -135,6 +135,26 @@
                                                     const MCSymbol *Sym) const {
 }
 
+static bool inExplicitSection(const GlobalObject *GO, SectionKind Kind) {
+  if (GO->hasSection())
+    return true;
+
+  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 true;
+    }
+  }
+
+  if (auto *F = dyn_cast<Function>(GO)) {
+    if (F->hasFnAttribute("implicit-section-name"))
+      return true;
+  }
+
+  return false;
+}
 
 /// getKindForGlobal - This is a top-level target-independent classifier for
 /// a global object.  Given a global variable and information from the TM, this
@@ -187,6 +207,15 @@
       if (!GVar->hasGlobalUnnamedAddr())
         return SectionKind::getReadOnly();
 
+      // If two globals with differing sizes end up in the same mergeable section that
+      // section can be assigned an incorrect entry size. To avoid this we do not put
+      // globals into a mergeable section if they have been explicitly assigned to a section.
+      // TODO: This is a pessimistic solution as we lose the benifits of mergeable sections. A
+      //       better solution might be to bin globals of the same size into difference mergeable
+      //       sections with the same name.
+      if (inExplicitSection(GO, SectionKind::getReadOnly()))
+        return SectionKind::getReadOnly();
+
       // If initializer is a null-terminated string, put it in a "cstring"
       // section of the right width.
       if (ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) {
@@ -245,24 +274,8 @@
 /// available externally) globals.
 MCSection *TargetLoweringObjectFile::SectionForGlobal(
     const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
-  // Select section name.
-  if (GO->hasSection())
+  if (inExplicitSection(GO, Kind))
     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);
 }
Index: llvm/test/CodeGen/X86/explict-section-mergeable.ll
===================================================================
--- /dev/null
+++ llvm/test/CodeGen/X86/explict-section-mergeable.ll
@@ -0,0 +1,22 @@
+; RUN: llc < %s -mtriple=x86_64-linux-gnu | FileCheck %s
+
+;; show that the implicitly generated sections are as expected
+@implicit1 = unnamed_addr constant [2 x i16] [i16 1, i16 1]
+; CHECK: .section .rodata.cst4,"aM",@progbits,4
+@implicit2 = unnamed_addr constant [2 x i32] [i32 1, i32 1]
+; CHECK: .section .rodata.cst8,"aM",@progbits,8
+@implicit3 = unnamed_addr constant [2 x i16] [i16 1, i16 0]
+; CHECK: .section .rodata.str2.2,"aMS",@progbits,2
+
+;; Check that an explicitly created section is not SHF_MERGE and that
+;; it contains all three symbols.
+@explicit1 = unnamed_addr constant [2 x i16] [i16 1, i16 1] "rodata-section"=".explicit"
+@explicit2 = unnamed_addr constant [2 x i32] [i32 1, i32 1] "rodata-section"=".explicit"
+@explicit3 = unnamed_addr constant [2 x i16] [i16 1, i16 0] "rodata-section"=".explicit"
+; CHECK: .section .explicit,"a",@progbits
+; CHECK-NOT: .section
+; CHECK: explicit1:
+; CHECK-NOT: .section
+; CHECK: explicit2:
+; CHECK-NOT: .section
+; CHECK: explicit3:
Index: llvm/test/CodeGen/X86/section_mergeable_size.ll
===================================================================
--- llvm/test/CodeGen/X86/section_mergeable_size.ll
+++ /dev/null
@@ -1,3 +0,0 @@
-; RUN: llc -mtriple x86_64-linux-gnu < %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