MC: adjust text section flags for WoA

Correct the section flags for code built for Windows on ARM with
`-ffunction-sections`.  Windows on ARM uses solely Thumb-2 instructions, and
indicates that the function is thumb by placing it in a text section that has
IMAGE_SCN_MEM_16BIT flag set.

When we encounter a .section directive, a new section is constructed.  This may
be a text segment.  In order to identify that we need the additional flag,
expose the target triple through the ObjectFileInfo as this information is lost
otherwise.

Since any modern ARM targeting environment on Windows would be Thumb-2 (Windows
ARM NT or Windows Embedded Compact), introducing a new flag to indicate the
section attribute seems to be a bit overkill.  Simply depend on the target
triple.  Since there is one location that this information is currently needed,
creating a target specific assembly parser and delegating the parsing of section
switches also feels a bit heavy handed.  If it turns out that this information
ends up changing additional behaviour, then it may be worth considering that
alternative.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@211481 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/MC/MCObjectFileInfo.h b/include/llvm/MC/MCObjectFileInfo.h
index 1a56040e4667a2f37c633d727be6114e863211b4..75294b5d7325eba67e6aacc844cc3f56a0eea10d 100644 (file)
--- a/include/llvm/MC/MCObjectFileInfo.h
+++ b/include/llvm/MC/MCObjectFileInfo.h
@@ -14,13 +14,13 @@
 #ifndef LLVM_MC_MCBJECTFILEINFO_H
 #define LLVM_MC_MCBJECTFILEINFO_H
 
+#include "llvm/ADT/Triple.h"
 #include "llvm/Support/CodeGen.h"
 
 namespace llvm {
   class MCContext;
   class MCSection;
   class StringRef;
-  class Triple;
 
 class MCObjectFileInfo {
 protected:
@@ -380,6 +380,7 @@ private:
   Reloc::Model RelocM;
   CodeModel::Model CMModel;
   MCContext *Ctx;
+  Triple TT;
 
   void InitMachOMCObjectFileInfo(Triple T);
   void InitELFMCObjectFileInfo(Triple T);
@@ -388,6 +389,9 @@ private:
   /// InitEHFrameSection - Initialize EHFrameSection on demand.
   ///
   void InitEHFrameSection();
+
+public:
+  const Triple &getTargetTriple() const { return TT; }
 };
 
 } // end namespace llvm

diff --git a/lib/MC/MCObjectFileInfo.cpp b/lib/MC/MCObjectFileInfo.cpp
index b76aaa47239857b2419fd4236a5c1447bdc83429..b9ba011a6731fbce5ea94b4329d678d2dc105d81 100644 (file)
--- a/lib/MC/MCObjectFileInfo.cpp
+++ b/lib/MC/MCObjectFileInfo.cpp
@@ -792,7 +792,7 @@ void MCObjectFileInfo::InitCOFFMCObjectFileInfo(Triple T) {
                         SectionKind::getDataRel());
 }
 
-void MCObjectFileInfo::InitMCObjectFileInfo(StringRef TT, Reloc::Model relocm,
+void MCObjectFileInfo::InitMCObjectFileInfo(StringRef T, Reloc::Model relocm,
                                             CodeModel::Model cm,
                                             MCContext &ctx) {
   RelocM = relocm;
@@ -817,8 +817,9 @@ void MCObjectFileInfo::InitMCObjectFileInfo(StringRef TT, Reloc::Model relocm,
   DwarfAccelNamespaceSection = nullptr; // Used only by selected targets.
   DwarfAccelTypesSection = nullptr;     // Used only by selected targets.
 
-  Triple T(TT);
-  Triple::ArchType Arch = T.getArch();
+  TT = Triple(T);
+
+  Triple::ArchType Arch = TT.getArch();
   // FIXME: Checking for Arch here to filter out bogus triples such as
   // cellspu-apple-darwin. Perhaps we should fix in Triple?
   if ((Arch == Triple::x86 || Arch == Triple::x86_64 ||
@@ -826,17 +827,17 @@ void MCObjectFileInfo::InitMCObjectFileInfo(StringRef TT, Reloc::Model relocm,
        Arch == Triple::arm64 || Arch == Triple::aarch64 ||
        Arch == Triple::ppc || Arch == Triple::ppc64 ||
        Arch == Triple::UnknownArch) &&
-      (T.isOSDarwin() || T.isOSBinFormatMachO())) {
+      (TT.isOSDarwin() || TT.isOSBinFormatMachO())) {
     Env = IsMachO;
-    InitMachOMCObjectFileInfo(T);
+    InitMachOMCObjectFileInfo(TT);
   } else if ((Arch == Triple::x86 || Arch == Triple::x86_64 ||
               Arch == Triple::arm || Arch == Triple::thumb) &&
-             (T.isOSWindows() && T.getObjectFormat() == Triple::COFF)) {
+             (TT.isOSWindows() && TT.getObjectFormat() == Triple::COFF)) {
     Env = IsCOFF;
-    InitCOFFMCObjectFileInfo(T);
+    InitCOFFMCObjectFileInfo(TT);
   } else {
     Env = IsELF;
-    InitELFMCObjectFileInfo(T);
+    InitELFMCObjectFileInfo(TT);
   }
 }
 

diff --git a/lib/MC/MCParser/COFFAsmParser.cpp b/lib/MC/MCParser/COFFAsmParser.cpp
index 8e8447f7b89bc99b547bc7003621e6f022588f39..0d914efe8748b1bf453eea378ad346469cb20409 100644 (file)
--- a/lib/MC/MCParser/COFFAsmParser.cpp
+++ b/lib/MC/MCParser/COFFAsmParser.cpp
@@ -13,6 +13,7 @@
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCExpr.h"
+#include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCParser/MCAsmLexer.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSectionCOFF.h"
@@ -378,6 +379,11 @@ bool COFFAsmParser::ParseDirectiveSection(StringRef, SMLoc) {
     return TokError("unexpected token in directive");
 
   SectionKind Kind = computeSectionKind(Flags);
+  if (Kind.isText()) {
+    const Triple &T = getContext().getObjectFileInfo()->getTargetTriple();
+    if (T.getArch() == Triple::arm || T.getArch() == Triple::thumb)
+      Flags |= COFF::IMAGE_SCN_MEM_16BIT;
+  }
   ParseSectionSwitch(SectionName, Flags, Kind, COMDATSymName, Type);
   return false;
 }

diff --git a/test/MC/ARM/Windows/multiple-text-sections.s b/test/MC/ARM/Windows/multiple-text-sections.s
new file mode 100644 (file)
index 0000000..241eee4
--- /dev/null
+++ b/test/MC/ARM/Windows/multiple-text-sections.s
@@ -0,0 +1,58 @@
+@ RUN: llvm-mc -triple thumbv7-windows-itanium -filetype obj -o - %s \
+@ RUN:   | llvm-readobj -s - | FileCheck %s
+
+       .syntax unified
+       .text
+       .thumb
+
+       .section        .text,"xr",one_only,a
+
+       .def     a;
+               .scl    2;
+               .type   32;
+       .endef
+a:
+       movs    r0, #65
+       bx      lr
+
+       .section        .text,"xr",one_only,b
+
+       .def     b;
+               .scl    2;
+               .type   32;
+       .endef
+       .thumb_func
+b:
+       movs    r0, #66
+       bx      lr
+
+@ CHECK: Sections [
+@ CHECK:   Section {
+@ CHECK:     Name: .text
+@ CHECK:     Characteristics [
+@ CHECK:       IMAGE_SCN_CNT_CODE
+@ CHECK:       IMAGE_SCN_MEM_16BIT
+@ CHECK:       IMAGE_SCN_MEM_EXECUTE
+@ CHECK:       IMAGE_SCN_MEM_READ
+@ CHECK:     ]
+@ CHECK:   }
+@ CHECK:   Section {
+@ CHECK:     Name: .text
+@ CHECK:     Characteristics [
+@ CHECK:       IMAGE_SCN_CNT_CODE
+@ CHECK:       IMAGE_SCN_MEM_16BIT
+@ CHECK:       IMAGE_SCN_MEM_EXECUTE
+@ CHECK:       IMAGE_SCN_MEM_READ
+@ CHECK:     ]
+@ CHECK:   }
+@ CHECK:   Section {
+@ CHECK:     Name: .text
+@ CHECK:     Characteristics [
+@ CHECK:       IMAGE_SCN_CNT_CODE
+@ CHECK:       IMAGE_SCN_MEM_16BIT
+@ CHECK:       IMAGE_SCN_MEM_EXECUTE
+@ CHECK:       IMAGE_SCN_MEM_READ
+@ CHECK:     ]
+@ CHECK:   }
+@ CHECK: ]
+