llvm-6502/unittests/Transforms/IPO/LowerBitSets.cpp
Peter Collingbourne 5a81e14385 Introduce bitset metadata format and bitset lowering pass.
This patch introduces a new mechanism that allows IR modules to co-operatively
build pointer sets corresponding to addresses within a given set of
globals. One particular use case for this is to allow a C++ program to
efficiently verify (at each call site) that a vtable pointer is in the set
of valid vtable pointers for the class or its derived classes. One way of
doing this is for a toolchain component to build, for each class, a bit set
that maps to the memory region allocated for the vtables, such that each 1
bit in the bit set maps to a valid vtable for that class, and lay out the
vtables next to each other, to minimize the total size of the bit sets.

The patch introduces a metadata format for representing pointer sets, an
'@llvm.bitset.test' intrinsic and an LTO lowering pass that lays out the globals
and builds the bitsets, and documents the new feature.

Differential Revision: http://reviews.llvm.org/D7288

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@230054 91177308-0d34-0410-b5e6-96231b3b80d8
2015-02-20 20:30:47 +00:00

65 lines
1.8 KiB
C++

//===- LowerBitSets.cpp - Unit tests for bitset lowering ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/IPO/LowerBitSets.h"
#include "gtest/gtest.h"
using namespace llvm;
TEST(LowerBitSets, BitSetBuilder) {
struct {
std::vector<uint64_t> Offsets;
std::vector<uint8_t> Bits;
uint64_t ByteOffset;
uint64_t BitSize;
unsigned AlignLog2;
bool IsSingleOffset;
} BSBTests[] = {
{{}, {0}, 0, 1, 0, false},
{{0}, {1}, 0, 1, 0, true},
{{4}, {1}, 4, 1, 0, true},
{{37}, {1}, 37, 1, 0, true},
{{0, 1}, {3}, 0, 2, 0, false},
{{0, 4}, {3}, 0, 2, 2, false},
{{0, uint64_t(1) << 33}, {3}, 0, 2, 33, false},
{{3, 7}, {3}, 3, 2, 2, false},
{{0, 1, 7}, {131}, 0, 8, 0, false},
{{0, 2, 14}, {131}, 0, 8, 1, false},
{{0, 1, 8}, {3, 1}, 0, 9, 0, false},
{{0, 2, 16}, {3, 1}, 0, 9, 1, false},
};
for (auto &&T : BSBTests) {
BitSetBuilder BSB;
for (auto Offset : T.Offsets)
BSB.addOffset(Offset);
BitSetInfo BSI = BSB.build();
EXPECT_EQ(T.Bits, BSI.Bits);
EXPECT_EQ(T.ByteOffset, BSI.ByteOffset);
EXPECT_EQ(T.BitSize, BSI.BitSize);
EXPECT_EQ(T.AlignLog2, BSI.AlignLog2);
EXPECT_EQ(T.IsSingleOffset, BSI.isSingleOffset());
for (auto Offset : T.Offsets)
EXPECT_TRUE(BSI.containsGlobalOffset(Offset));
auto I = T.Offsets.begin();
for (uint64_t NonOffset = 0; NonOffset != 256; ++NonOffset) {
if (I != T.Offsets.end() && *I == NonOffset) {
++I;
continue;
}
EXPECT_FALSE(BSI.containsGlobalOffset(NonOffset));
}
}
}