Remove the 's' DataLayout specification

During the years there have been some attempts at figuring out how to
align byval arguments. A look at the commit log suggests that they
were

* Use the ABI alignment.
* When that was not sufficient for x86-64, I added the 's' specification to
  DataLayout.
* When that was not sufficient Evan added the virtual getByValTypeAlignment.
* When even that was not sufficient, we just got the FE to add the alignment
  to the byval.

This patch is just a simple cleanup that removes my first attempt at fixing the
problem. I also added an AArch64 implementation of getByValTypeAlignment to
make sure this patch is a nop. I also left the 's' parsing for backward
compatibility.

I will send a short email to llvmdev about the change for anyone maintaining
an out of tree target.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198287 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.rst

@@ -1160,9 +1160,6 @@ as follows:
 ``a<size>:<abi>:<pref>``
     This specifies the alignment for an aggregate type of a given bit
     ``<size>``.
-``s<size>:<abi>:<pref>``
-    This specifies the alignment for a stack object of a given bit
-    ``<size>``.
 ``n<size1>:<size2>:<size3>...``
     This specifies a set of native integer widths for the target CPU in
     bits. For example, it might contain ``n32`` for 32-bit PowerPC,

include/llvm/IR/DataLayout.h

@@ -45,8 +45,7 @@ enum AlignTypeEnum {
   INTEGER_ALIGN = 'i',               ///< Integer type alignment
   VECTOR_ALIGN = 'v',                ///< Vector type alignment
   FLOAT_ALIGN = 'f',                 ///< Floating point type alignment
-  AGGREGATE_ALIGN = 'a',             ///< Aggregate alignment
+  AGGREGATE_ALIGN = 'a'              ///< Aggregate alignment
-  STACK_ALIGN = 's'                  ///< Stack objects alignment
 };
 
 /// Layout alignment element.
@@ -344,10 +343,6 @@ public:
   /// an integer type of the specified bitwidth.
   unsigned getABIIntegerTypeAlignment(unsigned BitWidth) const;
 
-  /// getCallFrameTypeAlignment - Return the minimum ABI-required alignment
-  /// for the specified type when it is part of a call frame.
-  unsigned getCallFrameTypeAlignment(Type *Ty) const;
-
   /// getPrefTypeAlignment - Return the preferred stack/global alignment for
   /// the specified type.  This is always at least as good as the ABI alignment.
   unsigned getPrefTypeAlignment(Type *Ty) const;

lib/CodeGen/TargetLoweringBase.cpp

@@ -1285,7 +1285,7 @@ void llvm::GetReturnInfo(Type* ReturnType, AttributeSet attr,
 /// function arguments in the caller parameter area.  This is the actual
 /// alignment, not its logarithm.
 unsigned TargetLoweringBase::getByValTypeAlignment(Type *Ty) const {
-  return TD->getCallFrameTypeAlignment(Ty);
+  return TD->getABITypeAlignment(Ty);
 }
 
 //===----------------------------------------------------------------------===//

lib/IR/DataLayout.cpp

@@ -225,6 +225,10 @@ void DataLayout::parseSpecifier(StringRef Desc) {
     Tok = Tok.substr(1);
 
     switch (Specifier) {
+    case 's':
+      // Ignored for backward compatibility.
+      // FIXME: remove this on LLVM 4.0.
+      break;
     case 'E':
       LittleEndian = false;
       break;
@@ -259,8 +263,7 @@ void DataLayout::parseSpecifier(StringRef Desc) {
     case 'i':
     case 'v':
     case 'f':
-    case 'a':
+    case 'a': {
-    case 's': {
       AlignTypeEnum AlignType;
       switch (Specifier) {
       default:
@@ -268,7 +271,6 @@ void DataLayout::parseSpecifier(StringRef Desc) {
       case 'v': AlignType = VECTOR_ALIGN; break;
       case 'f': AlignType = FLOAT_ALIGN; break;
       case 'a': AlignType = AGGREGATE_ALIGN; break;
-      case 's': AlignType = STACK_ALIGN; break;
       }
 
       // Bit size.
@@ -617,14 +619,6 @@ unsigned DataLayout::getABIIntegerTypeAlignment(unsigned BitWidth) const {
   return getAlignmentInfo(INTEGER_ALIGN, BitWidth, true, 0);
 }
 
-unsigned DataLayout::getCallFrameTypeAlignment(Type *Ty) const {
-  for (unsigned i = 0, e = Alignments.size(); i != e; ++i)
-    if (Alignments[i].AlignType == STACK_ALIGN)
-      return Alignments[i].ABIAlign;
-
-  return getABITypeAlignment(Ty);
-}
-
 unsigned DataLayout::getPrefTypeAlignment(Type *Ty) const {
   return getAlignment(Ty, false);
 }

lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -1346,6 +1346,12 @@ AArch64TargetLowering::LowerReturn(SDValue Chain,
                      &RetOps[0], RetOps.size());
 }
 
+unsigned AArch64TargetLowering::getByValTypeAlignment(Type *Ty) const {
+  // This is a new backend. For anything more precise than this a FE should
+  // set an explicit alignment.
+  return 4;
+}
+
 SDValue
 AArch64TargetLowering::LowerCall(CallLoweringInfo &CLI,
                                  SmallVectorImpl<SDValue> &InVals) const {

lib/Target/AArch64/AArch64ISelLowering.h

@@ -221,6 +221,8 @@ public:
                       const SmallVectorImpl<SDValue> &OutVals,
                       SDLoc dl, SelectionDAG &DAG) const;
 
+  virtual unsigned getByValTypeAlignment(Type *Ty) const LLVM_OVERRIDE;
+
   SDValue LowerCall(CallLoweringInfo &CLI,
                     SmallVectorImpl<SDValue> &InVals) const;
 

lib/Target/AArch64/AArch64TargetMachine.cpp

@@ -34,7 +34,7 @@ AArch64TargetMachine::AArch64TargetMachine(const Target &T, StringRef TT,
   : LLVMTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL),
     Subtarget(TT, CPU, FS),
     InstrInfo(Subtarget),
-    DL("e-i64:64-i128:128-s:32-n32:64-S128"),
+    DL("e-i64:64-i128:128-n32:64-S128"),
     TLInfo(*this),
     TSInfo(*this),
     FrameLowering(Subtarget) {

lib/Target/Target.cpp

@@ -113,7 +113,7 @@ unsigned LLVMABIAlignmentOfType(LLVMTargetDataRef TD, LLVMTypeRef Ty) {
 }
 
 unsigned LLVMCallFrameAlignmentOfType(LLVMTargetDataRef TD, LLVMTypeRef Ty) {
-  return unwrap(TD)->getCallFrameTypeAlignment(unwrap(Ty));
+  return unwrap(TD)->getABITypeAlignment(unwrap(Ty));
 }
 
 unsigned LLVMPreferredAlignmentOfType(LLVMTargetDataRef TD, LLVMTypeRef Ty) {

lib/Target/X86/X86TargetMachine.cpp

@@ -53,10 +53,6 @@ static std::string computeDataLayout(const X86Subtarget &ST) {
   else
     Ret += "-f80:32";
 
-  // Objects on the stack ore aligned to 64 bits.
-  if (ST.is64Bit())
-    Ret += "-s:64";
-
   // The registers can hold 8, 16, 32 or, in x86-64, 64 bits.
   if (ST.is64Bit())
     Ret += "-n8:16:32:64";