[llvm] [llubi] Implements common library functions (PR #190147)

[Nikita Popov via llvm-commits]

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@@ -0,0 +1,319 @@
+//===- Library.cpp - Library calls for llubi ------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements common libcalls for llubi.
+//
+//===----------------------------------------------------------------------===//
+
+#include "Library.h"
+#include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/InstrTypes.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/raw_ostream.h"
+
+namespace llvm::ubi {
+
+static uint64_t getMaxAlign(const DataLayout &DL) {
+  // Return an alignment of 16 for 64-bit platforms, and 8 for 32-bit ones.
+  return DL.getPointerABIAlignment(0).value() >= 8 ? 16 : 8;
+}
+
+Library::Library(Context &Ctx, EventHandler &Handler, const DataLayout &DL,
+                 ExecutorBase &Executor)
+    : Ctx(Ctx), Handler(Handler), DL(DL), Executor(Executor) {}
+
+std::optional<std::string> Library::readStringFromMemory(const Pointer &Ptr) {
+  auto *MO = Ptr.getMemoryObject();
+  if (!MO) {
+    Executor.reportImmediateUB(
+        "Invalid memory access via a pointer with nullary "
+        "provenance.");
+    return std::nullopt;
+  }
+
+  std::string Result;
+  const uint64_t Address = Ptr.address().getZExtValue();
+  uint64_t Offset = 0;
+
+  while (true) {
+    auto ValidOffset = Executor.verifyMemAccess(
+        *MO, APInt(DL.getPointerSizeInBits(0), Address + Offset), 1, Align(1),
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nikic wrote:

Why is the converting the address APInt to uint64_t first and then recreating the APInt here? Can stay in APInt?

https://github.com/llvm/llvm-project/pull/190147