Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com>, Timm =?utf-8?q?Bäder?= <tbae...@redhat.com> Message-ID: In-Reply-To: <llvm.org/llvm/llvm-project/pull/68...@github.com>
================ @@ -0,0 +1,452 @@ +//===--- InterpBitcast.cpp - Interpreter for the constexpr VM ---*- C++ -*-===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +#include "Boolean.h" +#include "Interp.h" +#include "PrimType.h" +#include "clang/AST/ASTContext.h" +#include "clang/AST/RecordLayout.h" +#include "clang/Basic/Builtins.h" +#include "clang/Basic/TargetInfo.h" +#include "llvm/ADT/BitVector.h" + +namespace clang { +namespace interp { + +/// Used to iterate over pointer fields. +using DataFunc = + llvm::function_ref<bool(const Pointer &P, PrimType Ty, size_t BitOffset)>; + +#define BITCAST_TYPE_SWITCH(Expr, B) \ + do { \ + switch (Expr) { \ + TYPE_SWITCH_CASE(PT_Sint8, B) \ + TYPE_SWITCH_CASE(PT_Uint8, B) \ + TYPE_SWITCH_CASE(PT_Sint16, B) \ + TYPE_SWITCH_CASE(PT_Uint16, B) \ + TYPE_SWITCH_CASE(PT_Sint32, B) \ + TYPE_SWITCH_CASE(PT_Uint32, B) \ + TYPE_SWITCH_CASE(PT_Sint64, B) \ + TYPE_SWITCH_CASE(PT_Uint64, B) \ + TYPE_SWITCH_CASE(PT_IntAP, B) \ + TYPE_SWITCH_CASE(PT_IntAPS, B) \ + TYPE_SWITCH_CASE(PT_Bool, B) \ + default: \ + llvm_unreachable("Unhandled bitcast type"); \ + } \ + } while (0) + +/// Float is a special case that sometimes needs the floating point semantics +/// to be available. +#define BITCAST_TYPE_SWITCH_WITH_FLOAT(Expr, B) \ + do { \ + switch (Expr) { \ + TYPE_SWITCH_CASE(PT_Sint8, B) \ + TYPE_SWITCH_CASE(PT_Uint8, B) \ + TYPE_SWITCH_CASE(PT_Sint16, B) \ + TYPE_SWITCH_CASE(PT_Uint16, B) \ + TYPE_SWITCH_CASE(PT_Sint32, B) \ + TYPE_SWITCH_CASE(PT_Uint32, B) \ + TYPE_SWITCH_CASE(PT_Sint64, B) \ + TYPE_SWITCH_CASE(PT_Uint64, B) \ + TYPE_SWITCH_CASE(PT_IntAP, B) \ + TYPE_SWITCH_CASE(PT_IntAPS, B) \ + TYPE_SWITCH_CASE(PT_Bool, B) \ + TYPE_SWITCH_CASE(PT_Float, B) \ + default: \ + llvm_unreachable("Unhandled bitcast type"); \ + } \ + } while (0) + +/// Rotate things around for big endian targets. +static void swapBytes(std::byte *M, size_t N) { + for (size_t I = 0; I != (N / 2); ++I) + std::swap(M[I], M[N - 1 - I]); +} + +/// Track what bits have been initialized to known values and which ones +/// have indeterminate value. +/// All offsets are in bits. +struct BitTracker { + llvm::BitVector Initialized; + llvm::BitVector Data; + + BitTracker() = default; + + size_t size() const { + assert(Initialized.size() == Data.size()); + return Initialized.size(); + } + + const std::byte *getBytes(size_t BitOffset, int a) { + assert(BitOffset % 8 == 0); + return reinterpret_cast<const std::byte *>(Data.getData().data()) + + (BitOffset / 8); + } + + bool allInitialized(size_t Offset, size_t Size) const { + return Initialized.find_first_unset_in(Offset, Offset + Size) == -1; + } + + bool allInitialized() const { return Initialized.all(); } + + void pushData(const std::byte *data, size_t BitOffset, size_t BitWidth) { + assert(BitOffset >= Data.size()); + Data.reserve(BitOffset + BitWidth); + Initialized.reserve(BitOffset + BitWidth); + + // First, fill up the bit vector until BitOffset. The bits are all 0 + // but we record them as indeterminate. + { + Data.resize(BitOffset, false); + Initialized.resize(BitOffset, false); + } + + size_t BitsHandled = 0; + // Read all full bytes first + for (size_t I = 0; I != BitWidth / 8; ++I) { + for (unsigned X = 0; X != 8; ++X) { + Data.push_back((data[I] & std::byte(1 << X)) != std::byte{0}); + Initialized.push_back(true); + ++BitsHandled; + } + } ---------------- sethp wrote: I'll defer to your expertise as to whether this is appropriate, here, but it does seem a little unfortunate to do a bit-by-bit copy. I think the in-band type information means we're more or less stuck doing things field-by-field (because `Interp` will lay out a `struct { char c[3]; };` very differently from a `struct { char c; short s; }`?), as with the existing ExprConstant interpreter, but my intuition says that I ought to expect a `uint64_t` field to take roughly 8x as long to copy as a `char` with this implementation, despite both of them fitting within a machine word on my 64-bit system. Does my thinking match yours, here? https://github.com/llvm/llvm-project/pull/68288 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
