r285544 - Add support for __builtin_alloca_with_align

[Hal Finkel via cfe-commits]

Hi David,

On Reid's patch for this (D25581), Richard said, "This takes the alignment in bits? That's so ridiculously dumb that I would feel bad about accepting this patch unless it comes with a warning for people writing the obvious-but-wrong __builtin_alloca_with_align(sizeof(T), alignof(T))". We should add the warning.

Thanks again,
Hal

----- Original Message -----
> From: "David Majnemer via cfe-commits" <cfe-commits at lists.llvm.org>
> To: cfe-commits at lists.llvm.org
> Sent: Monday, October 31, 2016 12:37:49 AM
> Subject: r285544 - Add support for __builtin_alloca_with_align
> 
> Author: majnemer
> Date: Mon Oct 31 00:37:48 2016
> New Revision: 285544
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=285544&view=rev
> Log:
> Add support for __builtin_alloca_with_align
> 
> __builtin_alloca always uses __BIGGEST_ALIGNMENT__ for the alignment
> of
> the allocation.  __builtin_alloca_with_align allows the programmer to
> specify the alignment of the allocation.
> 
> This fixes PR30658.
> 
> Added:
>     cfe/trunk/test/Sema/builtin-alloca-with-align.c
> Modified:
>     cfe/trunk/include/clang/Basic/Builtins.def
>     cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>     cfe/trunk/include/clang/Sema/Sema.h
>     cfe/trunk/lib/CodeGen/CGBuiltin.cpp
>     cfe/trunk/lib/Sema/SemaChecking.cpp
>     cfe/trunk/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
>     cfe/trunk/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp
>     cfe/trunk/test/CodeGen/builtins-ms.c
> 
> Modified: cfe/trunk/include/clang/Basic/Builtins.def
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/Builtins.def?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/Builtins.def (original)
> +++ cfe/trunk/include/clang/Basic/Builtins.def Mon Oct 31 00:37:48
> 2016
> @@ -512,6 +512,7 @@ BUILTIN(__builtin_unreachable, "v", "nr"
>  BUILTIN(__builtin_shufflevector, "v."   , "nc")
>  BUILTIN(__builtin_convertvector, "v."   , "nct")
>  BUILTIN(__builtin_alloca, "v*z"   , "Fn")
> +BUILTIN(__builtin_alloca_with_align, "v*zIz", "Fn")
>  BUILTIN(__builtin_call_with_static_chain, "v.", "nt")
>  
>  // "Overloaded" Atomic operator builtins.  These are overloaded to
>  support data
> 
> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Mon Oct 31
> 00:37:48 2016
> @@ -2440,6 +2440,10 @@ def err_no_accessor_for_property : Error
>  def error_cannot_find_suitable_accessor : Error<
>    "cannot find suitable %select{getter|setter}0 for property %1">;
>  
> +def err_alignment_too_small : Error<
> +  "requested alignment must be %0 or greater">;
> +def err_alignment_too_big : Error<
> +  "requested alignment must be %0 or smaller">;
>  def err_alignment_not_power_of_two : Error<
>    "requested alignment is not a power of 2">;
>  def err_alignment_dependent_typedef_name : Error<
> 
> Modified: cfe/trunk/include/clang/Sema/Sema.h
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Sema/Sema.h (original)
> +++ cfe/trunk/include/clang/Sema/Sema.h Mon Oct 31 00:37:48 2016
> @@ -9719,6 +9719,7 @@ public:
>  
>  private:
>    bool SemaBuiltinPrefetch(CallExpr *TheCall);
> +  bool SemaBuiltinAllocaWithAlign(CallExpr *TheCall);
>    bool SemaBuiltinAssume(CallExpr *TheCall);
>    bool SemaBuiltinAssumeAligned(CallExpr *TheCall);
>    bool SemaBuiltinLongjmp(CallExpr *TheCall);
> 
> Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Mon Oct 31 00:37:48 2016
> @@ -1147,6 +1147,19 @@ RValue CodeGenFunction::EmitBuiltinExpr(
>      AI->setAlignment(SuitableAlignmentInBytes);
>      return RValue::get(AI);
>    }
> +
> +  case Builtin::BI__builtin_alloca_with_align: {
> +    Value *Size = EmitScalarExpr(E->getArg(0));
> +    Value *AlignmentValue = EmitScalarExpr(E->getArg(1));
> +    auto *AlignmentCI = cast<ConstantInt>(AlignmentValue);
> +    unsigned Alignment = AlignmentCI->getZExtValue();
> +    const TargetInfo &TI = getContext().getTargetInfo();
> +    unsigned AlignmentInBytes = Alignment / TI.getCharWidth();
> +    AllocaInst *AI = Builder.CreateAlloca(Builder.getInt8Ty(),
> Size);
> +    AI->setAlignment(AlignmentInBytes);
> +    return RValue::get(AI);
> +  }
> +
>    case Builtin::BIbzero:
>    case Builtin::BI__builtin_bzero: {
>      Address Dest = EmitPointerWithAlignment(E->getArg(0));
> 
> Modified: cfe/trunk/lib/Sema/SemaChecking.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaChecking.cpp Mon Oct 31 00:37:48 2016
> @@ -791,6 +791,10 @@ Sema::CheckBuiltinFunctionCall(FunctionD
>      if (SemaBuiltinPrefetch(TheCall))
>        return ExprError();
>      break;
> +  case Builtin::BI__builtin_alloca_with_align:
> +    if (SemaBuiltinAllocaWithAlign(TheCall))
> +      return ExprError();
> +    break;
>    case Builtin::BI__assume:
>    case Builtin::BI__builtin_assume:
>      if (SemaBuiltinAssume(TheCall))
> @@ -3902,6 +3906,36 @@ bool Sema::SemaBuiltinAssume(CallExpr *T
>  
>    return false;
>  }
> +
> +/// Handle __builtin_assume_aligned. This is declared
> +/// as (size_t, size_t) where the second size_t must be a power of 2
> greater
> +/// than 8.
> +bool Sema::SemaBuiltinAllocaWithAlign(CallExpr *TheCall) {
> +  // The alignment must be a constant integer.
> +  Expr *Arg = TheCall->getArg(1);
> +
> +  // We can't check the value of a dependent argument.
> +  if (!Arg->isTypeDependent() && !Arg->isValueDependent()) {
> +    llvm::APSInt Result = Arg->EvaluateKnownConstInt(Context);
> +
> +    if (!Result.isPowerOf2())
> +      return Diag(TheCall->getLocStart(),
> +                  diag::err_alignment_not_power_of_two)
> +           << Arg->getSourceRange();
> +
> +    if (Result < Context.getCharWidth())
> +      return Diag(TheCall->getLocStart(),
> diag::err_alignment_too_small)
> +           << (unsigned)Context.getCharWidth()
> +           << Arg->getSourceRange();
> +
> +    if (Result > INT32_MAX)
> +      return Diag(TheCall->getLocStart(),
> diag::err_alignment_too_big)
> +           << INT32_MAX
> +           << Arg->getSourceRange();
> +  }
> +
> +  return false;
> +}
>  
>  /// Handle __builtin_assume_aligned. This is declared
>  /// as (const void*, size_t, ...) and can take one optional constant
>  int arg.
> 
> Modified:
> cfe/trunk/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
> (original)
> +++ cfe/trunk/lib/StaticAnalyzer/Checkers/BuiltinFunctionChecker.cpp
> Mon Oct 31 00:37:48 2016
> @@ -55,6 +55,7 @@ bool BuiltinFunctionChecker::evalCall(co
>      return true;
>    }
>  
> +  case Builtin::BI__builtin_alloca_with_align:
>    case Builtin::BI__builtin_alloca: {
>      // FIXME: Refactor into StoreManager itself?
>      MemRegionManager& RM = C.getStoreManager().getRegionManager();
> 
> Modified: cfe/trunk/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp
> (original)
> +++ cfe/trunk/lib/StaticAnalyzer/Checkers/UnixAPIChecker.cpp Mon Oct
> 31 00:37:48 2016
> @@ -43,6 +43,7 @@ public:
>    void CheckReallocZero(CheckerContext &C, const CallExpr *CE)
>    const;
>    void CheckReallocfZero(CheckerContext &C, const CallExpr *CE)
>    const;
>    void CheckAllocaZero(CheckerContext &C, const CallExpr *CE) const;
> +  void CheckAllocaWithAlignZero(CheckerContext &C, const CallExpr
> *CE) const;
>    void CheckVallocZero(CheckerContext &C, const CallExpr *CE) const;
>  
>    typedef void (UnixAPIChecker::*SubChecker)(CheckerContext &,
> @@ -337,6 +338,11 @@ void UnixAPIChecker::CheckAllocaZero(Che
>    BasicAllocationCheck(C, CE, 1, 0, "alloca");
>  }
>  
> +void UnixAPIChecker::CheckAllocaWithAlignZero(CheckerContext &C,
> +                                              const CallExpr *CE)
> const {
> +  BasicAllocationCheck(C, CE, 2, 0, "__builtin_alloca_with_align");
> +}
> +
>  void UnixAPIChecker::CheckVallocZero(CheckerContext &C,
>                                       const CallExpr *CE) const {
>    BasicAllocationCheck(C, CE, 1, 0, "valloc");
> @@ -366,6 +372,8 @@ void UnixAPIChecker::checkPreStmt(const
>        .Case("realloc", &UnixAPIChecker::CheckReallocZero)
>        .Case("reallocf", &UnixAPIChecker::CheckReallocfZero)
>        .Cases("alloca", "__builtin_alloca",
>        &UnixAPIChecker::CheckAllocaZero)
> +      .Case("__builtin_alloca_with_align",
> +            &UnixAPIChecker::CheckAllocaWithAlignZero)
>        .Case("valloc", &UnixAPIChecker::CheckVallocZero)
>        .Default(nullptr);
>  
> 
> Modified: cfe/trunk/test/CodeGen/builtins-ms.c
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/builtins-ms.c?rev=285544&r1=285543&r2=285544&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGen/builtins-ms.c (original)
> +++ cfe/trunk/test/CodeGen/builtins-ms.c Mon Oct 31 00:37:48 2016
> @@ -1,9 +1,16 @@
>  // RUN: %clang_cc1 %s -emit-llvm -o - -fms-extensions -triple
>  i686-pc-win32 | FileCheck %s
>  
> -// CHECK-LABEL: define void @test_alloca
> +// CHECK-LABEL: define void @test_alloca(
>  void capture(void *);
>  void test_alloca(int n) {
>    capture(_alloca(n));
>    // CHECK: %[[arg:.*]] = alloca i8, i32 %{{.*}}, align 16
>    // CHECK: call void @capture(i8* %[[arg]])
>  }
> +
> +// CHECK-LABEL: define void @test_alloca_with_align(
> +void test_alloca_with_align(int n) {
> +  capture(__builtin_alloca_with_align(n, 64));
> +  // CHECK: %[[arg:.*]] = alloca i8, i32 %{{.*}}, align 8
> +  // CHECK: call void @capture(i8* %[[arg]])
> +}
> 
> Added: cfe/trunk/test/Sema/builtin-alloca-with-align.c
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Sema/builtin-alloca-with-align.c?rev=285544&view=auto
> ==============================================================================
> --- cfe/trunk/test/Sema/builtin-alloca-with-align.c (added)
> +++ cfe/trunk/test/Sema/builtin-alloca-with-align.c Mon Oct 31
> 00:37:48 2016
> @@ -0,0 +1,29 @@
> +// RUN: %clang_cc1 -fsyntax-only -verify %s
> +
> +void test1(int a) {
> +  __builtin_alloca_with_align(a, 32);
> +}
> +
> +void test2(int a) {
> +  __builtin_alloca_with_align(a, -32); // expected-error {{requested
> alignment is not a power of 2}}
> +}
> +
> +void test3(unsigned *b) {
> +  __builtin_alloca_with_align(b, 32); // expected-warning
> {{incompatible pointer to integer conversion passing 'unsigned int
> *' to parameter of type}}
> +}
> +
> +void test4(int a) {
> +  __builtin_alloca_with_align(a, 32, 0); // expected-error {{too
> many arguments to function call, expected 2, have 3}}
> +}
> +
> +void test5(int a) {
> +  __builtin_alloca_with_align(a, 31); // expected-error {{requested
> alignment is not a power of 2}}
> +}
> +
> +void test6(int a, int j) {
> +  __builtin_alloca_with_align(a, j); // expected-error {{must be a
> constant integer}}
> +}
> +
> +void test7(int a) {
> +  __builtin_alloca_with_align(a, 2); // expected-error {{requested
> alignment must be 8 or greater}}
> +}
> 
> 
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory