[ARM] Fix Thumb text sections' flags under COFF/Windows

The main issue here is that the "thumb" flag wasn't set for some of these
sections, making MSVC's link.exe fails to correctly relocate code
against the symbols inside these sections. link.exe could fail for
instance with the "fixup is not aligned for target 'XX'" error. If
linking doesn't fail, the relocation process goes wrong in the end and
invalid code is generated by the linker.

This patch adds Thumb/ARM information so that the right flags are set
on COFF/Windows.

Patch by Adrien Guinet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@273880 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 6d5dd5fa4d5a98cc21de7b698888547c7458514f..a8e854ecbee0d481ab60de4691d9ddfce31f9109 100644 (file)
--- a/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -809,8 +809,9 @@ void TargetLoweringObjectFileMachO::getNameWithPrefix(
 //===----------------------------------------------------------------------===//
 
 static unsigned
-getCOFFSectionFlags(SectionKind K) {
+getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
   unsigned Flags = 0;
+  bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
 
   if (K.isMetadata())
     Flags |=
@@ -819,7 +820,8 @@ getCOFFSectionFlags(SectionKind K) {
     Flags |=
       COFF::IMAGE_SCN_MEM_EXECUTE |
       COFF::IMAGE_SCN_MEM_READ |
-      COFF::IMAGE_SCN_CNT_CODE;
+      COFF::IMAGE_SCN_CNT_CODE |
+      (isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
   else if (K.isBSS())
     Flags |=
       COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
@@ -889,7 +891,7 @@ MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
     const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
     const TargetMachine &TM) const {
   int Selection = 0;
-  unsigned Characteristics = getCOFFSectionFlags(Kind);
+  unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
   StringRef Name = GV->getSection();
   StringRef COMDATSymName = "";
   if (GV->hasComdat()) {
@@ -938,7 +940,7 @@ MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
 
   if ((EmitUniquedSection && !Kind.isCommon()) || GV->hasComdat()) {
     const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
-    unsigned Characteristics = getCOFFSectionFlags(Kind);
+    unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
 
     Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
     int Selection = getSelectionForCOFF(GV);
@@ -1015,7 +1017,7 @@ MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
 
   SectionKind Kind = SectionKind::getReadOnly();
   const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
-  unsigned Characteristics = getCOFFSectionFlags(Kind);
+  unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
   Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
   unsigned UniqueID = NextUniqueID++;
 

diff --git a/lib/MC/MCObjectFileInfo.cpp b/lib/MC/MCObjectFileInfo.cpp
index 5bbc8d5c5a925dfd9f0430e57fbf61574ebe262a..d05bcea14c98250335463b92c60ca2d4efecd38e 100644 (file)
--- a/lib/MC/MCObjectFileInfo.cpp
+++ b/lib/MC/MCObjectFileInfo.cpp
@@ -595,7 +595,10 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
                        COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
       SectionKind::getData());
 
-  bool IsWoA = T.getArch() == Triple::arm || T.getArch() == Triple::thumb;
+  // Set the `IMAGE_SCN_MEM_16BIT` flag when compiling for thumb mode.  This is
+  // used to indicate to the linker that the text segment contains thumb instructions
+  // and to set the ISA selection bit for calls accordingly.
+  const bool IsThumb = T.getArch() == Triple::thumb;
 
   CommDirectiveSupportsAlignment = true;
 
@@ -606,7 +609,7 @@ void MCObjectFileInfo::initCOFFMCObjectFileInfo(const Triple &T) {
       SectionKind::getBSS());
   TextSection = Ctx->getCOFFSection(
       ".text",
-      (IsWoA ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |
+      (IsThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0) |
           COFF::IMAGE_SCN_CNT_CODE | COFF::IMAGE_SCN_MEM_EXECUTE |
           COFF::IMAGE_SCN_MEM_READ,
       SectionKind::getText());