[clang] [clang] Constexpr for __builtin_shufflevector and __builtin_convertvector (PR #76615)
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Sat Dec 30 05:15:47 PST 2023
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Pol M (Destroyerrrocket)
<details>
<summary>Changes</summary>
Summary:
This patch adds constexpr support for __builtin_shufflevector and __builtin_convertvector.
A small oddity encountered was that the arg to the intrinsics may be an lvalue without any sort of implicit cast of any kind. I solved this through the EvaluateVectorOrLValue function, which treats the lvalue as if it was in an rvalue cast, which gets me the desired vector.
---
Full diff: https://github.com/llvm/llvm-project/pull/76615.diff
4 Files Affected:
- (modified) clang/docs/LanguageExtensions.rst (+3-2)
- (modified) clang/docs/ReleaseNotes.rst (+2)
- (modified) clang/lib/AST/ExprConstant.cpp (+137-1)
- (modified) clang/test/Sema/constant-builtins-2.c (+61)
``````````diff
diff --git a/clang/docs/LanguageExtensions.rst b/clang/docs/LanguageExtensions.rst
index 23a7f4f5d5b926..5f06c3d4b86f94 100644
--- a/clang/docs/LanguageExtensions.rst
+++ b/clang/docs/LanguageExtensions.rst
@@ -2853,7 +2853,7 @@ Query for this feature with ``__has_builtin(__builtin_dump_struct)``
``__builtin_shufflevector`` is used to express generic vector
permutation/shuffle/swizzle operations. This builtin is also very important
for the implementation of various target-specific header files like
-``<xmmintrin.h>``.
+``<xmmintrin.h>``. This builtin can be used within constant expressions.
**Syntax**:
@@ -2907,7 +2907,8 @@ Query for this feature with ``__has_builtin(__builtin_shufflevector)``.
``__builtin_convertvector`` is used to express generic vector
type-conversion operations. The input vector and the output vector
-type must have the same number of elements.
+type must have the same number of elements. This builtin can be used within
+constant expressions.
**Syntax**:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 0c8fec691bf3c9..b6f1407436ed4f 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -237,6 +237,8 @@ Non-comprehensive list of changes in this release
* Since MSVC 19.33 added undocumented attribute ``[[msvc::constexpr]]``, this release adds the attribute as well.
* Added ``#pragma clang fp reciprocal``.
+* Builtins ``__builtin_shufflevector()`` and ``__builtin_convertvector()`` may now be used within constant
+ expressions.
New Compiler Flags
------------------
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index f6aeee1a4e935d..e8afa10fe7aaac 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2702,7 +2702,8 @@ static bool checkFloatingPointResult(EvalInfo &Info, const Expr *E,
static bool HandleFloatToFloatCast(EvalInfo &Info, const Expr *E,
QualType SrcType, QualType DestType,
APFloat &Result) {
- assert(isa<CastExpr>(E) || isa<CompoundAssignOperator>(E));
+ assert(isa<CastExpr>(E) || isa<CompoundAssignOperator>(E) ||
+ isa<ConvertVectorExpr>(E));
llvm::RoundingMode RM = getActiveRoundingMode(Info, E);
APFloat::opStatus St;
APFloat Value = Result;
@@ -10643,6 +10644,9 @@ namespace {
bool VisitUnaryImag(const UnaryOperator *E);
bool VisitBinaryOperator(const BinaryOperator *E);
bool VisitUnaryOperator(const UnaryOperator *E);
+ bool VisitConvertVectorExpr(const ConvertVectorExpr *E);
+ bool VisitShuffleVectorExpr(const ShuffleVectorExpr *E);
+
// FIXME: Missing: conditional operator (for GNU
// conditional select), shufflevector, ExtVectorElementExpr
};
@@ -10895,6 +10899,138 @@ bool VectorExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
return Success(APValue(ResultElements.data(), ResultElements.size()), E);
}
+static bool EvaluateVectorOrLValue(APValue &Result, EvalInfo &Info,
+ const Expr *E, const QualType &Type) {
+ if (!Evaluate(Result, Info, E))
+ return false;
+
+ if (Result.isLValue()) {
+ // Source of the data is an lvalue; Manually handle the lvalue as if
+ // it was an rvalue to get the current APValue.
+ LValue LValueFound;
+ LValueFound.setFrom(Info.Ctx, Result);
+ if (!handleLValueToRValueConversion(Info, E, Type, LValueFound, Result)) {
+ return false;
+ }
+ }
+
+ if (!Result.isVector()) {
+ return false;
+ }
+ return true;
+}
+
+static bool handleVectorConversion(EvalInfo &Info, const FPOptions FPO,
+ const Expr *E, QualType SourceTy,
+ QualType DestTy, APValue const &Original,
+ APValue &Result) {
+ if (SourceTy->isIntegerType()) {
+ if (DestTy->isRealFloatingType()) {
+ Result = APValue(APFloat(0.0));
+ return HandleIntToFloatCast(Info, E, FPO, SourceTy, Original.getInt(),
+ DestTy, Result.getFloat());
+ }
+ if (DestTy->isIntegerType()) {
+ Result = APValue(
+ HandleIntToIntCast(Info, E, DestTy, SourceTy, Original.getInt()));
+ return true;
+ }
+ } else if (SourceTy->isRealFloatingType()) {
+ if (DestTy->isRealFloatingType()) {
+ Result = Original;
+ return HandleFloatToFloatCast(Info, E, SourceTy, DestTy,
+ Result.getFloat());
+ }
+ if (DestTy->isIntegerType()) {
+ Result = APValue(APSInt());
+ return HandleFloatToIntCast(Info, E, SourceTy, Original.getFloat(),
+ DestTy, Result.getInt());
+ }
+ }
+ return false;
+}
+
+bool VectorExprEvaluator::VisitConvertVectorExpr(const ConvertVectorExpr *E) {
+ APValue Source;
+ QualType SourceVecType = E->getSrcExpr()->getType();
+ if (!EvaluateVectorOrLValue(Source, Info, E->getSrcExpr(), SourceVecType))
+ return false;
+
+ QualType DestTy = E->getType()->castAs<VectorType>()->getElementType();
+ QualType SourceTy = SourceVecType->castAs<VectorType>()->getElementType();
+
+ const FPOptions FPO = E->getFPFeaturesInEffect(Info.Ctx.getLangOpts());
+
+ SmallVector<APValue, 4> ResultElements;
+ ResultElements.reserve(Source.getVectorLength());
+ for (unsigned EltNum = 0; EltNum < Source.getVectorLength(); ++EltNum) {
+ APValue Elt;
+ if (!handleVectorConversion(Info, FPO, E, SourceTy, DestTy,
+ Source.getVectorElt(EltNum), Elt))
+ return false;
+ ResultElements.push_back(std::move(Elt));
+ }
+
+ return Success(APValue(ResultElements.data(), ResultElements.size()), E);
+}
+
+static bool handleVectorShuffle(EvalInfo &Info, const ShuffleVectorExpr *E,
+ QualType ElemType, APValue const &VecVal1,
+ APValue const &VecVal2, unsigned EltNum,
+ APValue &Result) {
+ unsigned const TotalElementsInAVector = VecVal1.getVectorLength();
+
+ Expr const *IndexExpr = E->getExpr(2 + EltNum);
+ APSInt IndexVal;
+ if (!EvaluateInteger(IndexExpr, IndexVal, Info)) {
+ return false;
+ }
+
+ uint32_t index = IndexVal.getZExtValue();
+ // The spec says that -1 should be treated as undef for optimizations,
+ // but in constexpr we need to choose a value. We'll choose 0.
+ if (index >= TotalElementsInAVector * 2) {
+ index = 0;
+ }
+
+ if (index >= TotalElementsInAVector) {
+ Result = VecVal2.getVectorElt(index - TotalElementsInAVector);
+ } else {
+ Result = VecVal1.getVectorElt(index);
+ }
+ return true;
+}
+
+bool VectorExprEvaluator::VisitShuffleVectorExpr(const ShuffleVectorExpr *E) {
+ APValue VecVal1;
+ const Expr *Vec1 = E->getExpr(0);
+ if (!EvaluateVectorOrLValue(VecVal1, Info, Vec1, Vec1->getType()))
+ return false;
+ APValue VecVal2;
+ const Expr *Vec2 = E->getExpr(1);
+ if (!EvaluateVectorOrLValue(VecVal2, Info, Vec2, Vec2->getType()))
+ return false;
+
+ VectorType const *DestVecTy = E->getType()->castAs<VectorType>();
+ if (!DestVecTy) {
+ return false;
+ }
+ QualType DestElTy = DestVecTy->getElementType();
+
+ auto TotalElementsInOutputVector = DestVecTy->getNumElements();
+
+ SmallVector<APValue, 4> ResultElements;
+ ResultElements.reserve(TotalElementsInOutputVector);
+ for (unsigned EltNum = 0; EltNum < TotalElementsInOutputVector; ++EltNum) {
+ APValue Elt;
+ if (!handleVectorShuffle(Info, E, DestElTy, VecVal1, VecVal2, EltNum, Elt))
+ return false;
+ ResultElements.push_back(std::move(Elt));
+ }
+
+ return Success(APValue(ResultElements.data(), ResultElements.size()), E);
+}
+
//===----------------------------------------------------------------------===//
// Array Evaluation
//===----------------------------------------------------------------------===//
diff --git a/clang/test/Sema/constant-builtins-2.c b/clang/test/Sema/constant-builtins-2.c
index 2bdd7b06daabfe..c6bb602149e193 100644
--- a/clang/test/Sema/constant-builtins-2.c
+++ b/clang/test/Sema/constant-builtins-2.c
@@ -302,3 +302,64 @@ extern __typeof__(__builtin_expect(0, 0)) bi0;
// Strings
int array1[__builtin_strlen("ab\0cd")];
int array2[(sizeof(array1)/sizeof(int)) == 2? 1 : -1];
+
+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 short vector4short __attribute__((__vector_size__(8)));
+typedef char vector4char __attribute__((__vector_size__(4)));
+typedef double vector8double __attribute__((__vector_size__(64)));
+typedef float vector8float __attribute__((__vector_size__(32)));
+typedef long long vector8long __attribute__((__vector_size__(64)));
+typedef int vector8int __attribute__((__vector_size__(32)));
+typedef short vector8short __attribute__((__vector_size__(16)));
+typedef char vector8char __attribute__((__vector_size__(8)));
+
+// Convert vector
+#define CHECK_NUM(__size, __typeFrom, __typeTo, ...) \
+ vector##__size##__typeTo \
+ from_##vector##__size##__typeFrom##_to_##vector##__size##__typeTo##_var = \
+ __builtin_convertvector((vector##__size##__typeFrom){__VA_ARGS__}, \
+ vector##__size##__typeTo);
+#define CHECK_TO_ALL_TYPES(__size, __typeFrom, ...) \
+ CHECK_NUM(__size, __typeFrom, double, __VA_ARGS__) \
+ CHECK_NUM(__size, __typeFrom, float, __VA_ARGS__) \
+ CHECK_NUM(__size, __typeFrom, long, __VA_ARGS__) \
+ CHECK_NUM(__size, __typeFrom, int, __VA_ARGS__) \
+ CHECK_NUM(__size, __typeFrom, short, __VA_ARGS__) \
+ CHECK_NUM(__size, __typeFrom, char, __VA_ARGS__)
+
+#define CHECK_ALL_COMBINATIONS(__size, ...) \
+ CHECK_TO_ALL_TYPES(__size, double, __VA_ARGS__) \
+ CHECK_TO_ALL_TYPES(__size, float, __VA_ARGS__) \
+ CHECK_TO_ALL_TYPES(__size, long, __VA_ARGS__) \
+ CHECK_TO_ALL_TYPES(__size, int, __VA_ARGS__) \
+ CHECK_TO_ALL_TYPES(__size, short, __VA_ARGS__) \
+ CHECK_TO_ALL_TYPES(__size, char, __VA_ARGS__)
+
+CHECK_ALL_COMBINATIONS(4, 0, 1, 2, 3);
+CHECK_ALL_COMBINATIONS(8, 0, 1, 2, 3, 4, 5, 6, 7);
+#undef CHECK_ALL_COMBINATIONS
+#undef CHECK_TO_ALL_TYPES
+#undef CHECK_NUM
+
+// Shuffle vector
+vector4int const vector4intConst1 = {0, 1, 2, 3};
+vector4int const vector4intConst2 = {4, 5, 6, 7};
+vector8int const vector8intConst = {};
+
+vector4int vectorShuffle1 =
+ __builtin_shufflevector(vector4intConst1, vector4intConst2, 0, 1, 2, 3);
+vector4int vectorShuffle2 =
+ __builtin_shufflevector(vector4intConst1, vector4intConst2, 4, 5, 6, 7);
+vector4int vectorShuffle3 =
+ __builtin_shufflevector(vector4intConst1, vector4intConst2, -1, -1, -1, -1);
+vector4int vectorShuffle4 =
+ __builtin_shufflevector(vector4intConst1, vector4intConst2, 0, 2, 4, 6);
+vector8int vectorShuffle5 = __builtin_shufflevector(
+ vector8intConst, vector8intConst, 0, 2, 4, 6, 8, 10, 12, 14);
+vector4int vectorShuffle6 = __builtin_shufflevector(
+ vector8intConst, vector8intConst, 0, 2, 4, 6);
+vector8int vectorShuffle7 =
+ __builtin_shufflevector(vector4intConst1, vector4intConst2, 0, 2, 4, 6, 1, 3, 5, 7);
``````````
</details>
https://github.com/llvm/llvm-project/pull/76615
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