[clang] [clang] Implement constexpr bit_cast for vectors (PR #66894)
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Sun Sep 24 04:53:38 PDT 2023
https://github.com/DaMatrix updated https://github.com/llvm/llvm-project/pull/66894
>From 8768741800aae37a825864e2ee782484ed073ce9 Mon Sep 17 00:00:00 2001
From: DaPorkchop_ <daporkchop at daporkchop.net>
Date: Sun, 13 Aug 2023 22:39:12 +0200
Subject: [PATCH] [clang] Implement constexpr bit_cast for vectors
---
clang/lib/AST/ExprConstant.cpp | 181 ++++++++++++------
.../SemaCXX/constexpr-builtin-bit-cast.cpp | 38 ++++
2 files changed, 162 insertions(+), 57 deletions(-)
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index fea06b97259fe31..8cd6a0e390ee0f8 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -2732,6 +2732,92 @@ static bool truncateBitfieldValue(EvalInfo &Info, const Expr *E,
return true;
}
+static bool BitcastAPIntToVector(EvalInfo &Info, const VectorType *VTy,
+ const llvm::APInt &SValInt,
+ SmallVectorImpl<APValue> &Elts) {
+ QualType EltTy = VTy->getElementType();
+ unsigned NElts = VTy->getNumElements();
+ unsigned EltSize =
+ VTy->isExtVectorBoolType() ? 1 : Info.Ctx.getTypeSize(EltTy);
+
+ if ((NElts * EltSize) % Info.Ctx.getCharWidth() != 0) {
+ // The vector's size in bits is not a multiple of the target's byte size,
+ // so its layout is unspecified. For now, we'll simply treat these cases as
+ // unsupported (this should only be possible with OpenCL bool vectors whose
+ // element count isn't a multiple of the byte size).
+ return false;
+ }
+
+ Elts.reserve(NElts);
+ bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
+ if (EltTy->isRealFloatingType()) {
+ const llvm::fltSemantics &Sem = Info.Ctx.getFloatTypeSemantics(EltTy);
+ unsigned FloatEltSize = EltSize;
+ if (&Sem == &APFloat::x87DoubleExtended())
+ FloatEltSize = 80;
+ for (unsigned i = 0; i < NElts; i++) {
+ llvm::APInt Elt;
+ if (BigEndian)
+ Elt = SValInt.rotl(i * EltSize + FloatEltSize).trunc(FloatEltSize);
+ else
+ Elt = SValInt.rotr(i * EltSize).trunc(FloatEltSize);
+ Elts.push_back(APValue(APFloat(Sem, Elt)));
+ }
+ } else if (EltTy->isIntegerType()) {
+ for (unsigned i = 0; i < NElts; i++) {
+ llvm::APInt Elt;
+ if (BigEndian)
+ Elt = SValInt.rotl(i * EltSize + EltSize).zextOrTrunc(EltSize);
+ else
+ Elt = SValInt.rotr(i * EltSize).zextOrTrunc(EltSize);
+ Elts.push_back(APValue(APSInt(Elt, !EltTy->isSignedIntegerType())));
+ }
+ } else {
+ return false;
+ }
+ return true;
+}
+
+static bool BitcastVectorToAPInt(EvalInfo &Info, const VectorType *VTy,
+ const APValue &SVal, llvm::APInt &Res) {
+ QualType EltTy = VTy->getElementType();
+ unsigned NElts = VTy->getNumElements();
+ unsigned EltSize =
+ VTy->isExtVectorBoolType() ? 1 : Info.Ctx.getTypeSize(EltTy);
+ unsigned VecSize = Info.Ctx.getTypeSize(VTy);
+
+ if ((NElts * EltSize) % Info.Ctx.getCharWidth() != 0) {
+ // The vector's size in bits is not a multiple of the target's byte size,
+ // so its layout is unspecified. For now, we'll simply treat these cases as
+ // unsupported (this should only be possible with OpenCL bool vectors whose
+ // element count isn't a multiple of the byte size).
+ return false;
+ }
+
+ bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
+ Res = llvm::APInt::getZero(VecSize);
+ for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
+ const APValue &Elt = SVal.getVectorElt(i);
+ llvm::APInt EltAsInt;
+ if (Elt.isInt()) {
+ EltAsInt = Elt.getInt();
+ } else if (Elt.isFloat()) {
+ EltAsInt = Elt.getFloat().bitcastToAPInt();
+ } else {
+ // Don't try to handle vectors of anything other than int or float
+ // (not sure if it's possible to hit this case).
+ return false;
+ }
+ unsigned BaseEltSize = EltAsInt.getBitWidth();
+ if (BigEndian)
+ Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i * EltSize + BaseEltSize);
+ else
+ Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i * EltSize);
+ }
+
+ return true;
+}
+
static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
llvm::APInt &Res) {
APValue SVal;
@@ -2745,34 +2831,9 @@ static bool EvalAndBitcastToAPInt(EvalInfo &Info, const Expr *E,
Res = SVal.getFloat().bitcastToAPInt();
return true;
}
- if (SVal.isVector()) {
- QualType VecTy = E->getType();
- unsigned VecSize = Info.Ctx.getTypeSize(VecTy);
- QualType EltTy = VecTy->castAs<VectorType>()->getElementType();
- unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
- bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
- Res = llvm::APInt::getZero(VecSize);
- for (unsigned i = 0; i < SVal.getVectorLength(); i++) {
- APValue &Elt = SVal.getVectorElt(i);
- llvm::APInt EltAsInt;
- if (Elt.isInt()) {
- EltAsInt = Elt.getInt();
- } else if (Elt.isFloat()) {
- EltAsInt = Elt.getFloat().bitcastToAPInt();
- } else {
- // Don't try to handle vectors of anything other than int or float
- // (not sure if it's possible to hit this case).
- Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
- return false;
- }
- unsigned BaseEltSize = EltAsInt.getBitWidth();
- if (BigEndian)
- Res |= EltAsInt.zextOrTrunc(VecSize).rotr(i*EltSize+BaseEltSize);
- else
- Res |= EltAsInt.zextOrTrunc(VecSize).rotl(i*EltSize);
- }
+ if (SVal.isVector() &&
+ BitcastVectorToAPInt(Info, E->getType()->castAs<VectorType>(), SVal, Res))
return true;
- }
// Give up if the input isn't an int, float, or vector. For example, we
// reject "(v4i16)(intptr_t)&a".
Info.FFDiag(E, diag::note_invalid_subexpr_in_const_expr);
@@ -7005,10 +7066,11 @@ class APValueToBufferConverter {
return visitArray(Val, Ty, Offset);
case APValue::Struct:
return visitRecord(Val, Ty, Offset);
+ case APValue::Vector:
+ return visitVector(Val, Ty, Offset);
case APValue::ComplexInt:
case APValue::ComplexFloat:
- case APValue::Vector:
case APValue::FixedPoint:
// FIXME: We should support these.
@@ -7095,6 +7157,22 @@ class APValueToBufferConverter {
return true;
}
+ bool visitVector(const APValue &Val, QualType Ty, CharUnits Offset) {
+ const VectorType *VTy = Ty->castAs<VectorType>();
+
+ APInt Bits;
+ if (!BitcastVectorToAPInt(Info, VTy, Val, Bits))
+ return false;
+
+ assert(Bits.getBitWidth() == Info.Ctx.getTypeSize(Ty));
+
+ unsigned Width = Bits.getBitWidth();
+ SmallVector<uint8_t, 8> Bytes(Width / 8);
+ llvm::StoreIntToMemory(Bits, &*Bytes.begin(), Width / 8);
+ Buffer.writeObject(Offset, Bytes);
+ return true;
+ }
+
bool visitInt(const APSInt &Val, QualType Ty, CharUnits Offset) {
APSInt AdjustedVal = Val;
unsigned Width = AdjustedVal.getBitWidth();
@@ -7103,7 +7181,7 @@ class APValueToBufferConverter {
AdjustedVal = AdjustedVal.extend(Width);
}
- SmallVector<unsigned char, 8> Bytes(Width / 8);
+ SmallVector<uint8_t, 8> Bytes(Width / 8);
llvm::StoreIntToMemory(AdjustedVal, &*Bytes.begin(), Width / 8);
Buffer.writeObject(Offset, Bytes);
return true;
@@ -7304,6 +7382,21 @@ class BufferToAPValueConverter {
return ArrayValue;
}
+ std::optional<APValue> visit(const VectorType *Ty, CharUnits Offset) {
+ SmallVector<uint8_t, 8> Bytes;
+ if (!Buffer.readObject(Offset, Info.Ctx.getTypeSizeInChars(Ty), Bytes))
+ return std::nullopt;
+
+ APInt SValInt = APInt::getZero(Info.Ctx.getTypeSize(Ty));
+ llvm::LoadIntFromMemory(SValInt, &*Bytes.begin(), Bytes.size());
+
+ SmallVector<APValue, 4> Elts;
+ if (!BitcastAPIntToVector(Info, Ty, SValInt, Elts))
+ return std::nullopt;
+
+ return APValue(Elts.data(), Elts.size());
+ }
+
std::optional<APValue> visit(const Type *Ty, CharUnits Offset) {
return unsupportedType(QualType(Ty, 0));
}
@@ -10515,36 +10608,10 @@ bool VectorExprEvaluator::VisitCastExpr(const CastExpr *E) {
llvm::APInt SValInt;
if (!EvalAndBitcastToAPInt(Info, SE, SValInt))
return false;
- // Extract the elements
- QualType EltTy = VTy->getElementType();
- unsigned EltSize = Info.Ctx.getTypeSize(EltTy);
- bool BigEndian = Info.Ctx.getTargetInfo().isBigEndian();
+
SmallVector<APValue, 4> Elts;
- if (EltTy->isRealFloatingType()) {
- const llvm::fltSemantics &Sem = Info.Ctx.getFloatTypeSemantics(EltTy);
- unsigned FloatEltSize = EltSize;
- if (&Sem == &APFloat::x87DoubleExtended())
- FloatEltSize = 80;
- for (unsigned i = 0; i < NElts; i++) {
- llvm::APInt Elt;
- if (BigEndian)
- Elt = SValInt.rotl(i * EltSize + FloatEltSize).trunc(FloatEltSize);
- else
- Elt = SValInt.rotr(i * EltSize).trunc(FloatEltSize);
- Elts.push_back(APValue(APFloat(Sem, Elt)));
- }
- } else if (EltTy->isIntegerType()) {
- for (unsigned i = 0; i < NElts; i++) {
- llvm::APInt Elt;
- if (BigEndian)
- Elt = SValInt.rotl(i*EltSize+EltSize).zextOrTrunc(EltSize);
- else
- Elt = SValInt.rotr(i*EltSize).zextOrTrunc(EltSize);
- Elts.push_back(APValue(APSInt(Elt, !EltTy->isSignedIntegerType())));
- }
- } else {
+ if (!BitcastAPIntToVector(Info, VTy, SValInt, Elts))
return Error(E);
- }
return Success(Elts, E);
}
default:
diff --git a/clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp b/clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
index a6ebe0572d063bb..2b1c9a5d3ea8a7a 100644
--- a/clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
+++ b/clang/test/SemaCXX/constexpr-builtin-bit-cast.cpp
@@ -463,3 +463,41 @@ static_assert(bit_cast<long double>(ld539) == fivehundredandthirtynine, "");
static_assert(round_trip<__int128_t>(34.0L));
#endif
}
+
+namespace test_vector {
+
+typedef unsigned uint2 __attribute__((vector_size(2 * sizeof(unsigned))));
+typedef char byte8 __attribute__((vector_size(sizeof(unsigned long long))));
+
+constexpr uint2 test_vector = { 0x0C05FEFE, 0xCAFEBABE };
+
+static_assert(bit_cast<unsigned long long>(test_vector) == (LITTLE_END
+ ? 0xCAFEBABE0C05FEFE
+ : 0x0C05FEFECAFEBABE), "");
+
+static_assert(round_trip<uint2>(0xCAFEBABE0C05FEFEULL), "");
+static_assert(round_trip<byte8>(0xCAFEBABE0C05FEFEULL), "");
+
+typedef bool bool8 __attribute__((ext_vector_type(8)));
+typedef bool bool9 __attribute__((ext_vector_type(9)));
+typedef bool bool16 __attribute__((ext_vector_type(16)));
+typedef bool bool17 __attribute__((ext_vector_type(17)));
+typedef bool bool32 __attribute__((ext_vector_type(32)));
+typedef bool bool128 __attribute__((ext_vector_type(128)));
+
+static_assert(bit_cast<unsigned char>(bool8{1,0,1,0,1,0,1,0}) == (LITTLE_END ? 0x55 : 0xAA), "");
+static_assert(round_trip<bool8>(static_cast<unsigned char>(0)), "");
+static_assert(round_trip<bool8>(static_cast<unsigned char>(1)), "");
+static_assert(round_trip<bool8>(static_cast<unsigned char>(0x55)), "");
+
+static_assert(bit_cast<unsigned short>(bool16{1,1,1,1,1,0,0,0, 1,1,1,1,0,1,0,0}) == (LITTLE_END ? 0x2F1F : 0xF8F4), "");
+
+static_assert(round_trip<bool16>(static_cast<short>(0xCAFE)), "");
+static_assert(round_trip<bool32>(static_cast<int>(0xCAFEBABE)), "");
+static_assert(round_trip<bool128>(static_cast<__int128_t>(0xCAFEBABE0C05FEFEULL)), "");
+
+static_assert(bit_cast<unsigned short>(bool9{1,1,0,1,0,1,0,1,0}) == (LITTLE_END ? 0xAB : 0x1AA), ""); // expected-error{{static assertion expression is not an integral constant expression}}
+static_assert(round_trip<bool9>(static_cast<unsigned short>(0)), ""); // expected-error{{static assertion expression is not an integral constant expression}}
+static_assert(round_trip<bool17>(static_cast<unsigned int>(0x0001CAFE)), ""); // expected-error{{static assertion expression is not an integral constant expression}}
+
+}
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