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[clang] constexpr built-in reduce add function. #116243

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Merged
merged 4 commits into from
Nov 18, 2024
Merged

[clang] constexpr built-in reduce add function. #116243

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b2f4d35
constexpr reduce_add
c8ef Nov 14, 2024
e02f443
address review comments
c8ef Nov 15, 2024
a7d242b
add more test
c8ef Nov 15, 2024
9763439
Update clang/lib/AST/ExprConstant.cpp
c8ef Nov 18, 2024
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2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -353,6 +353,8 @@ Non-comprehensive list of changes in this release
The flexible array member (FAM) can now be accessed immediately without causing
issues with the sanitizer because the counter is automatically set.

- ``__builtin_reduce_add`` function can now be used in constant expressions.

New Compiler Flags
------------------

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2 changes: 1 addition & 1 deletion clang/include/clang/Basic/Builtins.td
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Expand Up @@ -1504,7 +1504,7 @@ def ReduceAnd : Builtin {

def ReduceAdd : Builtin {
let Spellings = ["__builtin_reduce_add"];
let Attributes = [NoThrow, Const, CustomTypeChecking];
let Attributes = [NoThrow, Const, CustomTypeChecking, Constexpr];
let Prototype = "void(...)";
}

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17 changes: 17 additions & 0 deletions clang/lib/AST/ExprConstant.cpp
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Expand Up @@ -13528,6 +13528,23 @@ bool IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
return Success(DidOverflow, E);
}

case Builtin::BI__builtin_reduce_add: {
APValue Source;
if (!EvaluateAsRValue(Info, E->getArg(0), Source))
return false;

unsigned SourceLen = Source.getVectorLength();
APSInt Reduced = Source.getVectorElt(0).getInt();
for (unsigned EltNum = 1; EltNum < SourceLen; ++EltNum) {
if (!CheckedIntArithmetic(
Info, E, Reduced, Source.getVectorElt(EltNum).getInt(),
Reduced.getBitWidth() + 1, std::plus<APSInt>(), Reduced))
return false;
}

return Success(Reduced, E);
}

case clang::X86::BI__builtin_ia32_addcarryx_u32:
case clang::X86::BI__builtin_ia32_addcarryx_u64:
case clang::X86::BI__builtin_ia32_subborrow_u32:
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22 changes: 22 additions & 0 deletions clang/test/Sema/constant_builtins_vector.cpp
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Expand Up @@ -19,6 +19,8 @@ typedef double vector4double __attribute__((__vector_size__(32)));
typedef float vector4float __attribute__((__vector_size__(16)));
typedef long long vector4long __attribute__((__vector_size__(32)));
typedef int vector4int __attribute__((__vector_size__(16)));
typedef unsigned long long vector4ulong __attribute__((__vector_size__(32)));
typedef unsigned int vector4uint __attribute__((__vector_size__(16)));
typedef short vector4short __attribute__((__vector_size__(8)));
typedef char vector4char __attribute__((__vector_size__(4)));
typedef BitInt8 vector4BitInt8 __attribute__((__vector_size__(4)));
Expand Down Expand Up @@ -723,3 +725,23 @@ not within the bounds of the input vectors; index of -1 found at position 0 is n
permitted in a constexpr context}}
vector4charConst1,
vector4charConst2, -1, -1, -1, -1);

static_assert(__builtin_reduce_add((vector4char){}) == 0);
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How is this handled? I'd have expected Source.getVectorElt(0).getInt() to have failed?

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I believe this is similar to zero initializing a vector with 4 char elements.

static_assert(__builtin_reduce_add((vector4char){1, 2, 3, 4}) == 10);
static_assert(__builtin_reduce_add((vector4short){10, 20, 30, 40}) == 100);
static_assert(__builtin_reduce_add((vector4int){100, 200, 300, 400}) == 1000);
static_assert(__builtin_reduce_add((vector4long){1000, 2000, 3000, 4000}) == 10000);
constexpr int reduceAddInt1 = __builtin_reduce_add((vector4int){~(1 << 31), 0, 0, 1});
// expected-error@-1 {{must be initialized by a constant expression}} \
// expected-note@-1 {{outside the range of representable values of type 'int'}}
constexpr long long reduceAddLong1 = __builtin_reduce_add((vector4long){~(1LL << 63), 0, 0, 1});
// expected-error@-1 {{must be initialized by a constant expression}} \
// expected-note@-1 {{outside the range of representable values of type 'long long'}}
constexpr int reduceAddInt2 = __builtin_reduce_add((vector4int){(1 << 31), 0, 0, -1});
// expected-error@-1 {{must be initialized by a constant expression}} \
// expected-note@-1 {{outside the range of representable values of type 'int'}}
constexpr long long reduceAddLong2 = __builtin_reduce_add((vector4long){(1LL << 63), 0, 0, -1});
// expected-error@-1 {{must be initialized by a constant expression}} \
// expected-note@-1 {{outside the range of representable values of type 'long long'}}
static_assert(__builtin_reduce_add((vector4uint){~0U, 0, 0, 1}) == 0);
static_assert(__builtin_reduce_add((vector4ulong){~0ULL, 0, 0, 1}) == 0);
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