Revert r363116 "[X86] [ABI] Fix i386 ABI "__m64" type bug"

This introduced MMX instructions in code that wasn't previously using
them, breaking programs using 64-bit vectors and x87 floating-point in
the same application. See discussion on the code review for more
details.

> According to System V i386 ABI: the  __m64 type paramater and return
> value are passed by MMX registers. But current implementation treats
> __m64 as i64 which results in parameter passing by stack and returning
> by EDX and EAX.
>
> This patch fixes the bug (https://bugs.llvm.org/show_bug.cgi?id=41029)
> for Linux and NetBSD.
>
> Patch by Wei Xiao (wxiao3)
>
> Differential Revision: https://reviews.llvm.org/D59744

llvm-svn: 363790

1 files changed, 20 insertions, 36 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index b1ff46049fa..9a991825dd1 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -915,6 +915,14 @@ ABIArgInfo PNaClABIInfo::classifyReturnType(QualType RetTy) const {
                                            : ABIArgInfo::getDirect());
 }
 
+/// IsX86_MMXType - Return true if this is an MMX type.
+bool IsX86_MMXType(llvm::Type *IRType) {
+  // Return true if the type is an MMX type <2 x i32>, <4 x i16>, or <8 x i8>.
+  return IRType->isVectorTy() && IRType->getPrimitiveSizeInBits() == 64 &&
+    cast<llvm::VectorType>(IRType)->getElementType()->isIntegerTy() &&
+    IRType->getScalarSizeInBits() != 64;
+}
+
 static llvm::Type* X86AdjustInlineAsmType(CodeGen::CodeGenFunction &CGF,
                                           StringRef Constraint,
                                           llvm::Type* Ty) {
@@ -1003,7 +1011,6 @@ class X86_32ABIInfo : public SwiftABIInfo {
   bool IsSoftFloatABI;
   bool IsMCUABI;
   unsigned DefaultNumRegisterParameters;
-  bool IsMMXEnabled;
 
   static bool isRegisterSize(unsigned Size) {
     return (Size == 8 || Size == 16 || Size == 32 || Size == 64);
@@ -1063,15 +1070,13 @@ public:
 
   X86_32ABIInfo(CodeGen::CodeGenTypes &CGT, bool DarwinVectorABI,
                 bool RetSmallStructInRegABI, bool Win32StructABI,
-                unsigned NumRegisterParameters, bool SoftFloatABI,
-                bool MMXEnabled)
+                unsigned NumRegisterParameters, bool SoftFloatABI)
     : SwiftABIInfo(CGT), IsDarwinVectorABI(DarwinVectorABI),
       IsRetSmallStructInRegABI(RetSmallStructInRegABI),
       IsWin32StructABI(Win32StructABI),
       IsSoftFloatABI(SoftFloatABI),
       IsMCUABI(CGT.getTarget().getTriple().isOSIAMCU()),
-      DefaultNumRegisterParameters(NumRegisterParameters),
-      IsMMXEnabled(MMXEnabled) {}
+      DefaultNumRegisterParameters(NumRegisterParameters) {}
 
   bool shouldPassIndirectlyForSwift(ArrayRef<llvm::Type*> scalars,
                                     bool asReturnValue) const override {
@@ -1086,30 +1091,16 @@ public:
     // x86-32 lowering does not support passing swifterror in a register.
     return false;
   }
-
-  bool isPassInMMXRegABI() const {
-    // The System V i386 psABI requires __m64 to be passed in MMX registers.
-    // Clang historically had a bug where it failed to apply this rule, and
-    // some platforms (e.g. Darwin, PS4, and FreeBSD) have opted to maintain
-    // compatibility with the old Clang behavior, so we only apply it on
-    // platforms that have specifically requested it (currently just Linux and
-    // NetBSD).
-    const llvm::Triple &T = getTarget().getTriple();
-    if (IsMMXEnabled && (T.isOSLinux() || T.isOSNetBSD()))
-      return true;
-    return false;
-  }
 };
 
 class X86_32TargetCodeGenInfo : public TargetCodeGenInfo {
 public:
   X86_32TargetCodeGenInfo(CodeGen::CodeGenTypes &CGT, bool DarwinVectorABI,
                           bool RetSmallStructInRegABI, bool Win32StructABI,
-                          unsigned NumRegisterParameters, bool SoftFloatABI,
-                          bool MMXEnabled = false)
+                          unsigned NumRegisterParameters, bool SoftFloatABI)
       : TargetCodeGenInfo(new X86_32ABIInfo(
             CGT, DarwinVectorABI, RetSmallStructInRegABI, Win32StructABI,
-            NumRegisterParameters, SoftFloatABI, MMXEnabled)) {}
+            NumRegisterParameters, SoftFloatABI)) {}
 
   static bool isStructReturnInRegABI(
       const llvm::Triple &Triple, const CodeGenOptions &Opts);
@@ -1395,9 +1386,10 @@ ABIArgInfo X86_32ABIInfo::classifyReturnType(QualType RetTy,
   }
 
   if (const VectorType *VT = RetTy->getAs<VectorType>()) {
-    uint64_t Size = getContext().getTypeSize(RetTy);
     // On Darwin, some vectors are returned in registers.
     if (IsDarwinVectorABI) {
+      uint64_t Size = getContext().getTypeSize(RetTy);
+
       // 128-bit vectors are a special case; they are returned in
       // registers and we need to make sure to pick a type the LLVM
       // backend will like.
@@ -1415,10 +1407,6 @@ ABIArgInfo X86_32ABIInfo::classifyReturnType(QualType RetTy,
       return getIndirectReturnResult(RetTy, State);
     }
 
-    if (VT->getElementType()->isIntegerType() && Size == 64 &&
-        isPassInMMXRegABI())
-      return ABIArgInfo::getDirect(llvm::Type::getX86_MMXTy(getVMContext()));
-
     return ABIArgInfo::getDirect();
   }
 
@@ -1713,26 +1701,23 @@ ABIArgInfo X86_32ABIInfo::classifyArgumentType(QualType Ty,
   }
 
   if (const VectorType *VT = Ty->getAs<VectorType>()) {
-    uint64_t Size = getContext().getTypeSize(Ty);
     // On Darwin, some vectors are passed in memory, we handle this by passing
     // it as an i8/i16/i32/i64.
     if (IsDarwinVectorABI) {
+      uint64_t Size = getContext().getTypeSize(Ty);
       if ((Size == 8 || Size == 16 || Size == 32) ||
           (Size == 64 && VT->getNumElements() == 1))
         return ABIArgInfo::getDirect(llvm::IntegerType::get(getVMContext(),
                                                             Size));
     }
 
-    if (VT->getElementType()->isIntegerType() && Size == 64) {
-      if (isPassInMMXRegABI())
-        return ABIArgInfo::getDirect(llvm::Type::getX86_MMXTy(getVMContext()));
-      else
-        return ABIArgInfo::getDirect(
-          llvm::IntegerType::get(getVMContext(), 64));
-    }
+    if (IsX86_MMXType(CGT.ConvertType(Ty)))
+      return ABIArgInfo::getDirect(llvm::IntegerType::get(getVMContext(), 64));
+
     return ABIArgInfo::getDirect();
   }
 
+
   if (const EnumType *EnumTy = Ty->getAs<EnumType>())
     Ty = EnumTy->getDecl()->getIntegerType();
 
@@ -9508,11 +9493,10 @@ const TargetCodeGenInfo &CodeGenModule::getTargetCodeGenInfo() {
           Types, IsDarwinVectorABI, RetSmallStructInRegABI,
           IsWin32FloatStructABI, CodeGenOpts.NumRegisterParameters));
     } else {
-      bool EnableMMX = getContext().getTargetInfo().getABI() != "no-mmx";
       return SetCGInfo(new X86_32TargetCodeGenInfo(
           Types, IsDarwinVectorABI, RetSmallStructInRegABI,
           IsWin32FloatStructABI, CodeGenOpts.NumRegisterParameters,
-          CodeGenOpts.FloatABI == "soft", EnableMMX));
+          CodeGenOpts.FloatABI == "soft"));
     }
   }