Add support for the x86 builtin __builtin_cpu_supports.

This matches the implementation of the gcc support for the same
feature, including checking the values set up by libgcc at runtime.
The structure looks like this:

  unsigned int __cpu_vendor;
  unsigned int __cpu_type;
  unsigned int __cpu_subtype;
  unsigned int __cpu_features[1];

with a set of enums to match various fields that are field out after
parsing the output of the cpuid instruction.
This also adds a set of errors checking for valid input (and cpu).

compiler-rt support for this and the other builtins in this family
(__builtin_cpu_init and __builtin_cpu_is) are forthcoming.

llvm-svn: 240994

Author: echristo

clang/include/clang/Basic/BuiltinsX86.def

@@ -24,6 +24,11 @@
 
 // FIXME: Are these nothrow/const?
 
+// Miscellaneous builtin for checking x86 cpu features.
+// TODO: Make this somewhat generic so that other backends
+// can use it?
+BUILTIN(__builtin_cpu_supports, "bcC*", "nc")
+
 // 3DNow!
 //
 BUILTIN(__builtin_ia32_femms, "v", "")

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -426,6 +426,7 @@ def warn_redecl_library_builtin : Warning<
   InGroup<DiagGroup<"incompatible-library-redeclaration">>;
 def err_builtin_definition : Error<"definition of builtin function %0">;
 def err_arm_invalid_specialreg : Error<"invalid special register for builtin">;
+def err_invalid_cpu_supports : Error<"invalid cpu feature string for builtin">;
 def warn_builtin_unknown : Warning<"use of unknown builtin %0">,
   InGroup<ImplicitFunctionDeclare>, DefaultError;
 def warn_dyn_class_memaccess : Warning<

clang/include/clang/Basic/TargetInfo.h

@@ -611,6 +611,9 @@ class TargetInfo : public RefCountedBase<TargetInfo> {
     }
   };
 
+  // Validate the contents of the __builtin_cpu_supports(const char*) argument.
+  virtual bool validateCpuSupports(StringRef Name) const { return false; }
+
   // validateOutputConstraint, validateInputConstraint - Checks that
   // a constraint is valid and provides information about it.
   // FIXME: These should return a real error instead of just true/false.

clang/include/clang/Sema/Sema.h

@@ -8734,6 +8734,7 @@ class Sema {
   bool SemaBuiltinARMSpecialReg(unsigned BuiltinID, CallExpr *TheCall,
                                 int ArgNum, unsigned ExpectedFieldNum,
                                 bool AllowName);
+  bool SemaBuiltinCpuSupports(CallExpr *TheCall);
 public:
   enum FormatStringType {
     FST_Scanf,

clang/lib/Basic/Targets.cpp

@@ -2215,6 +2215,7 @@ class X86TargetInfo : public TargetInfo {
     Names = AddlRegNames;
     NumNames = llvm::array_lengthof(AddlRegNames);
   }
+  bool validateCpuSupports(StringRef Name) const override;
   bool validateAsmConstraint(const char *&Name,
                              TargetInfo::ConstraintInfo &info) const override;
 
@@ -3338,6 +3339,33 @@ bool X86TargetInfo::hasFeature(StringRef Feature) const {
       .Default(false);
 }
 
+// We can't use a generic validation scheme for the features accepted here
+// versus subtarget features accepted in the target attribute because the
+// bitfield structure that's initialized in the runtime only supports the
+// below currently rather than the full range of subtarget features. (See
+// X86TargetInfo::hasFeature for a somewhat comprehensive list).
+bool X86TargetInfo::validateCpuSupports(StringRef FeatureStr) const {
+  return llvm::StringSwitch<bool>(FeatureStr)
+      .Case("cmov", true)
+      .Case("mmx", true)
+      .Case("popcnt", true)
+      .Case("sse", true)
+      .Case("sse2", true)
+      .Case("sse3", true)
+      .Case("sse4.1", true)
+      .Case("sse4.2", true)
+      .Case("avx", true)
+      .Case("avx2", true)
+      .Case("sse4a", true)
+      .Case("fma4", true)
+      .Case("xop", true)
+      .Case("fma", true)
+      .Case("avx512f", true)
+      .Case("bmi", true)
+      .Case("bmi2", true)
+      .Default(false);
+}
+
 bool
 X86TargetInfo::validateAsmConstraint(const char *&Name,
                                      TargetInfo::ConstraintInfo &Info) const {

clang/lib/CodeGen/CGBuiltin.cpp

@@ -6101,6 +6101,83 @@ Value *CodeGenFunction::EmitX86BuiltinExpr(unsigned BuiltinID,
 
   switch (BuiltinID) {
   default: return nullptr;
+  case X86::BI__builtin_cpu_supports: {
+    const Expr *FeatureExpr = E->getArg(0)->IgnoreParenCasts();
+    StringRef FeatureStr = cast<StringLiteral>(FeatureExpr)->getString();
+
+    // TODO: When/if this becomes more than x86 specific then use a TargetInfo
+    // based mapping.
+    // Processor features and mapping to processor feature value.
+    enum X86Features {
+      CMOV = 0,
+      MMX,
+      POPCNT,
+      SSE,
+      SSE2,
+      SSE3,
+      SSSE3,
+      SSE4_1,
+      SSE4_2,
+      AVX,
+      AVX2,
+      SSE4_A,
+      FMA4,
+      XOP,
+      FMA,
+      AVX512F,
+      BMI,
+      BMI2,
+      MAX
+    };
+
+    X86Features Feature = StringSwitch<X86Features>(FeatureStr)
+                              .Case("cmov", X86Features::CMOV)
+                              .Case("mmx", X86Features::MMX)
+                              .Case("popcnt", X86Features::POPCNT)
+                              .Case("sse", X86Features::SSE)
+                              .Case("sse2", X86Features::SSE2)
+                              .Case("sse3", X86Features::SSE3)
+                              .Case("sse4.1", X86Features::SSE4_1)
+                              .Case("sse4.2", X86Features::SSE4_2)
+                              .Case("avx", X86Features::AVX)
+                              .Case("avx2", X86Features::AVX2)
+                              .Case("sse4a", X86Features::SSE4_A)
+                              .Case("fma4", X86Features::FMA4)
+                              .Case("xop", X86Features::XOP)
+                              .Case("fma", X86Features::FMA)
+                              .Case("avx512f", X86Features::AVX512F)
+                              .Case("bmi", X86Features::BMI)
+                              .Case("bmi2", X86Features::BMI2)
+                              .Default(X86Features::MAX);
+    assert(Feature != X86Features::MAX && "Invalid feature!");
+
+    // Matching the struct layout from the compiler-rt/libgcc structure that is
+    // filled in:
+    // unsigned int __cpu_vendor;
+    // unsigned int __cpu_type;
+    // unsigned int __cpu_subtype;
+    // unsigned int __cpu_features[1];
+    llvm::Type *STy = llvm::StructType::get(
+        Int32Ty, Int32Ty, Int32Ty, llvm::ArrayType::get(Int32Ty, 1), nullptr);
+
+    // Grab the global __cpu_model.
+    llvm::Constant *CpuModel = CGM.CreateRuntimeVariable(STy, "__cpu_model");
+
+    // Grab the first (0th) element from the field __cpu_features off of the
+    // global in the struct STy.
+    Value *Idxs[] = {
+      ConstantInt::get(Int32Ty, 0),
+      ConstantInt::get(Int32Ty, 3),
+      ConstantInt::get(Int32Ty, 0)
+    };
+    Value *CpuFeatures = Builder.CreateGEP(STy, CpuModel, Idxs);
+    Value *Features = Builder.CreateLoad(CpuFeatures);
+
+    // Check the value of the bit corresponding to the feature requested.
+    Value *Bitset = Builder.CreateAnd(
+        Features, llvm::ConstantInt::get(Int32Ty, 1 << Feature));
+    return Builder.CreateICmpNE(Bitset, llvm::ConstantInt::get(Int32Ty, 0));
+  }
   case X86::BI_mm_prefetch: {
     Value *Address = EmitScalarExpr(E->getArg(0));
     Value *RW = ConstantInt::get(Int32Ty, 0);

clang/lib/Sema/SemaChecking.cpp

@@ -1031,6 +1031,8 @@ bool Sema::CheckX86BuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
   unsigned i = 0, l = 0, u = 0;
   switch (BuiltinID) {
   default: return false;
+  case X86::BI__builtin_cpu_supports:
+    return SemaBuiltinCpuSupports(TheCall);
   case X86::BI_mm_prefetch: i = 1; l = 0; u = 3; break;
   case X86::BI__builtin_ia32_sha1rnds4: i = 2, l = 0; u = 3; break;
   case X86::BI__builtin_ia32_vpermil2pd:
@@ -2782,6 +2784,26 @@ bool Sema::SemaBuiltinARMSpecialReg(unsigned BuiltinID, CallExpr *TheCall,
   return false;
 }
 
+/// SemaBuiltinCpuSupports - Handle __builtin_cpu_supports(char *).
+/// This checks that the target supports __builtin_cpu_supports and
+/// that the string argument is constant and valid.
+bool Sema::SemaBuiltinCpuSupports(CallExpr *TheCall) {
+  Expr *Arg = TheCall->getArg(0);
+
+  // Check if the argument is a string literal.
+  if (!isa<StringLiteral>(Arg->IgnoreParenImpCasts()))
+    return Diag(TheCall->getLocStart(), diag::err_expr_not_string_literal)
+           << Arg->getSourceRange();
+
+  // Check the contents of the string.
+  StringRef Feature =
+      cast<StringLiteral>(Arg->IgnoreParenImpCasts())->getString();
+  if (!Context.getTargetInfo().validateCpuSupports(Feature))
+    return Diag(TheCall->getLocStart(), diag::err_invalid_cpu_supports)
+           << Arg->getSourceRange();
+  return false;
+}
+
 /// SemaBuiltinLongjmp - Handle __builtin_longjmp(void *env[5], int val).
 /// This checks that the target supports __builtin_longjmp and
 /// that val is a constant 1.

clang/test/CodeGen/builtin-cpu-supports.c

@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -emit-llvm < %s| FileCheck %s
+
+// Test that we have the structure definition, the gep offsets, the name of the
+// global, the bit grab, and the icmp correct.
+extern void a(const char *);
+
+int main() {
+  if (__builtin_cpu_supports("sse4.2"))
+    a("sse4.2");
+
+  // CHECK: [[LOAD:%[^ ]+]] = load i32, i32* getelementptr inbounds ({ i32, i32, i32, [1 x i32] }, { i32, i32, i32, [1 x i32] }* @__cpu_model, i32 0, i32 3, i32 0)
+  // CHECK: [[AND:%[^ ]+]] = and i32 [[LOAD]], 256
+  // CHECK = icmp ne i32 [[AND]], 0
+
+  return 0;
+}

clang/test/Sema/builtin-cpu-supports.c

@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -fsyntax-only -triple x86_64-pc-linux-gnu -verify %s
+// RUN: %clang_cc1 -fsyntax-only -triple powerpc64le-linux-gnu -verify %s
+
+extern void a(const char *);
+
+extern const char *str;
+
+int main() {
+#ifdef __x86_64__
+  if (__builtin_cpu_supports("ss")) // expected-error {{invalid cpu feature string}}
+    a("sse4.2");
+
+  if (__builtin_cpu_supports(str)) // expected-error {{expression is not a string literal}}
+    a(str);
+#else
+  if (__builtin_cpu_supports("vsx")) // expected-error {{use of unknown builtin}}
+    a("vsx");
+#endif
+
+  return 0;
+}