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MC: fix text section characteristics for WoA
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link.exe requires that the text section has the IMAGE_SCN_MEM_16BIT flag set.
Otherwise, it will treat the function as ARM.  If this occurs, then jumps to the
function will fail, switching from thumb to ARM mode execution.

With this change, it is possible to link using the MSVC linker as well.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210415 91177308-0d34-0410-b5e6-96231b3b80d8
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compnerd committed Jun 8, 2014
1 parent 4a0c1d1 commit ea3ab85
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Showing 2 changed files with 33 additions and 0 deletions.
3 changes: 3 additions & 0 deletions lib/MC/MCObjectFileInfo.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -569,6 +569,8 @@ void MCObjectFileInfo::InitELFMCObjectFileInfo(Triple T) {


void MCObjectFileInfo::InitCOFFMCObjectFileInfo(Triple T) {
bool IsWoA = T.getArch() == Triple::arm || T.getArch() == Triple::thumb;

// The object file format cannot represent common symbols with explicit
// alignments.
CommDirectiveSupportsAlignment = false;
Expand All @@ -582,6 +584,7 @@ void MCObjectFileInfo::InitCOFFMCObjectFileInfo(Triple T) {
SectionKind::getBSS());
TextSection =
Ctx->getCOFFSection(".text",
(IsWoA ? COFF::IMAGE_SCN_MEM_16BIT : 0) |
COFF::IMAGE_SCN_CNT_CODE |
COFF::IMAGE_SCN_MEM_EXECUTE |
COFF::IMAGE_SCN_MEM_READ,
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30 changes: 30 additions & 0 deletions test/MC/ARM/Windows/text-attributes.s
Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
@ RUN: llvm-mc -triple thumbv7-windows-itanium -filetype obj -o - %s \
@ RUN: | llvm-readobj -s - | FileCheck %s

.syntax unified
.thumb

.text

.def function
.type 32
.scl 2
.endef
.global function
.thumb_func
function:
bx lr

@ CHECK: Sections [
@ CHECK: Section {
@ CHECK: Name: .text
@ CHECK: Characteristics [
@ CHECK: IMAGE_SCN_ALIGN_4BYTES
@ CHECK: IMAGE_SCN_CNT_CODE
@ CHECK: IMAGE_SCN_MEM_16BIT
@ CHECK: IMAGE_SCN_MEM_EXECUTE
@ CHECK: IMAGE_SCN_MEM_PURGEABLE
@ CHECK: IMAGE_SCN_MEM_READ
@ CHECK: ]
@ CHECK: }
@ CHECK: ]

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