[ARM/AArch64] Enforce alignment for bitfielded structs

When creating a global variable with a type of a struct with bitfields, we must
forcibly set the alignment of the global from the RecordDecl. We must do this so
that the proper bitfield alignment makes its way down to LLVM, since clang will
mangle the bitfields into one large type.

llvm-svn: 235976

2 files changed, 7 insertions, 0 deletions

diff --git a/clang/lib/Basic/TargetInfo.cpp b/clang/lib/Basic/TargetInfo.cpp
index 330258b025b..cb6449f9741 100644
--- a/clang/lib/Basic/TargetInfo.cpp
+++ b/clang/lib/Basic/TargetInfo.cpp
@@ -75,6 +75,7 @@ TargetInfo::TargetInfo(const llvm::Triple &T) : TargetOpts(), Triple(T) {
   RegParmMax = 0;
   SSERegParmMax = 0;
   HasAlignMac68kSupport = false;
+  EnforceBitfieldContainerAlignment = false;
 
   // Default to no types using fpret.
   RealTypeUsesObjCFPRet = 0;
diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 047cf0d5b5c..3d6f4f95944 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -3983,6 +3983,9 @@ class ARMTargetInfo : public TargetInfo {
 
     ZeroLengthBitfieldBoundary = 0;
 
+    // Enforce the alignment of bitfield structs
+    EnforceBitfieldContainerAlignment = true;
+
     // Thumb1 add sp, #imm requires the immediate value be multiple of 4,
     // so set preferred for small types to 32.
     if (T.isOSBinFormatMachO()) {
@@ -4825,6 +4828,9 @@ public:
     UseBitFieldTypeAlignment = true;
     UseZeroLengthBitfieldAlignment = true;
 
+    // Enforce the alignment of bitfield structs
+    EnforceBitfieldContainerAlignment = true;
+
     // AArch64 targets default to using the ARM C++ ABI.
     TheCXXABI.set(TargetCXXABI::GenericAArch64);
   }