XenonAnalyse: add synthetic PPC fixtures for switch-aware walker

Three test scenarios hand-crafted in-source from big-endian PPC
instruction words, no proprietary bytecode. Each exercises a
different path through Function::Analyze's new switchMap handling:

  1. Happy path: switchMap populated with an entry for the synthetic
     function's bctr. Walker pushes all 4 case labels + default as
     successor blocks; fn.size covers through the default block.

  2. Null-map safety: switchMap = nullptr. Walker uses legacy pre-
     patch behavior; discontinuity pass erases label blocks; fn.size
     covers only the pre-bctr head. Guards against the default-null
     behavior regressing.

  3. Wrong-map miss: switchMap populated but with an entry for an
     unrelated bctr VA. switchMap->find(our_bctr) misses; walker
     falls through to legacy. Guards against the switchMap handling
     spuriously firing on wrong entries.

Assertions use fprintf + return-1 rather than a test framework, to
keep the test self-contained. If the repository later adopts a
standard test runner (Catch2 / doctest / gtest), porting is
straightforward.

See tests/README.md for the manual build command until CMake
integration is decided.

Author: Uproared

XenonAnalyse/tests/README.md

@@ -0,0 +1,68 @@
+# XenonAnalyse tests
+
+Synthetic hand-crafted PPC bytecode fixtures for `Function::Analyze`'s
+switch-aware block walker.
+
+## Fixtures
+
+`switch_aware_walker_test.cpp` exercises three scenarios against a
+synthetic 4-case absolute-form switch function built in-source from
+hand-emitted big-endian instruction words:
+
+1. **Happy path** — `switchMap` populated. Walker pushes all 4 labels
+   + default as successor blocks, `fn.size` extends to cover through
+   the default block.
+2. **Null-map safety** — `switchMap = nullptr`. Walker uses legacy
+   pre-patch behavior; discontinuity pass erases the label blocks;
+   `fn.size` covers only the pre-bctr head.
+3. **Wrong-map miss** — `switchMap` populated, but with an entry for
+   an unrelated bctr VA. `switchMap->find(our_bctr)` returns `end()`;
+   walker falls through to legacy behavior.
+
+All three assert on `fn.size` landing in the expected range. The
+tests use `assert`-style `fprintf(stderr, "[FAIL ...]" ...) + return 1`
+rather than a framework, to keep the test self-contained (no new
+dependencies).
+
+## Running
+
+Compile against a built `LibXenonAnalyse` + `XenonUtils` + `disasm` +
+`fmt`. Example (from a VS 2022 Developer Command Prompt with LLVM in
+PATH, after building the rest of the tree):
+
+```
+cd XenonAnalyse/tests
+clang-cl /std:c++20 /EHsc /nologo ^
+  /I"..\" /I"..\..\XenonUtils" ^
+  switch_aware_walker_test.cpp ^
+  "..\..\build\XenonAnalyse\LibXenonAnalyse.lib" ^
+  "..\..\build\XenonUtils\XenonUtils.lib" ^
+  "..\..\build\thirdparty\disasm\disasm.lib" ^
+  "..\..\build\thirdparty\fmt\fmt.lib" ^
+  /link /OUT:walker_test.exe
+walker_test.exe
+```
+
+Expected:
+
+```
+[ok   happy-path] fn.base=0x10000, fn.size=0x38, blocks=7
+[ok   null-map ] fn.base=0x10000, fn.size=0x1C (pre-patch truncation preserved)
+[ok   wrong-map] fn.base=0x10000, fn.size=0x1C (unrelated map entry correctly ignored)
+
+All 3 tests PASSED
+```
+
+## CMake integration
+
+Not included in this commit. If the repository adopts a test-runner
+pattern, a minimal CMake shape would be:
+
+```cmake
+add_executable(xenonanalyse_switch_walker_test switch_aware_walker_test.cpp)
+target_link_libraries(xenonanalyse_switch_walker_test PRIVATE LibXenonAnalyse)
+add_test(NAME switch_walker COMMAND xenonanalyse_switch_walker_test)
+```
+
+Or as an opt-in build behind `-DXENONANALYSE_TESTS=ON`. Whatever
+convention the repository prefers.

XenonAnalyse/tests/switch_aware_walker_test.cpp

@@ -0,0 +1,219 @@
+// Tests for Function::Analyze's switch-aware block walker.
+//
+// Hand-crafted synthetic PPC bytecode; self-contained; no dependency
+// on any particular test corpus.
+//
+// Three scenarios:
+//   (1) happy path:      switchMap populated, walker pushes switch labels
+//   (2) null-map safety: switchMap == nullptr, walker uses legacy path
+//   (3) wrong-map miss:  switchMap populated but no entry for this bctr;
+//                        walker uses legacy path
+//
+// See tests/README.md for the build command and expected output.
+
+#include "function.h"
+#include <array>
+#include <cassert>
+#include <cstdint>
+#include <cstdio>
+#include <cstring>
+#include <vector>
+
+namespace {
+
+// Little helper to emit a big-endian 32-bit insn word into a byte vector.
+// Xenon is big-endian PPC; our synthetic blobs must match for the walker
+// to decode them correctly.
+void emitBE(std::vector<uint8_t>& out, uint32_t insn)
+{
+    out.push_back((insn >> 24) & 0xFF);
+    out.push_back((insn >> 16) & 0xFF);
+    out.push_back((insn >>  8) & 0xFF);
+    out.push_back((insn >>  0) & 0xFF);
+}
+
+// Encode a handful of PPC instructions we need for the synthetic
+// fixtures. These are standard encodings; values are cross-checked
+// against capstone decoding as a sanity step.
+constexpr uint32_t PPC_BLR  = 0x4E800020; // blr
+constexpr uint32_t PPC_BCTR = 0x4E800420; // bctr
+constexpr uint32_t PPC_NOP  = 0x60000000; // ori r0, r0, 0 == nop
+
+// cmplwi cr6, rA, imm16 — primary opcode 10, field cr=6, rA, imm.
+// Encoding: 001010 (6) | 110 (cr=6) | 0 | rA(5) | imm(16)
+// = 0x2B | (rA<<16) | imm
+uint32_t cmplwi_cr6(uint32_t rA, uint32_t imm)
+{
+    return 0x2B000000u | (rA << 16) | (imm & 0xFFFF);
+}
+
+// bgt cr6, BD — primary opcode 16, BO=12 (branch if true), BI=25 (cr6 gt).
+// BD is a signed 14-bit displacement in bytes (we pass the displacement).
+uint32_t bgt_cr6(int32_t displacement)
+{
+    // Encoding: 010000 | 01100 | 11001 | BD(14) | 00
+    return 0x41990000u | (uint32_t(displacement) & 0xFFFC);
+}
+
+// Build a minimal "switch function" synthetic fixture:
+//
+//   0x00: cmplwi cr6, r3, 3     ; 4 cases
+//   0x04: bgt cr6, +0x30        ; default @ 0x34
+//   0x08: (would be LIS/ADDI/RLWINM/LWZX/MTCTR — stubbed as nops here
+//          because our walker treats mtctr/bctr by opcode; the prior
+//          instructions only matter to XenonAnalyse's SCAN side, not
+//          to Function::Analyze's block walker)
+//   0x08: nop
+//   0x0C: nop
+//   0x10: nop
+//   0x14: nop
+//   0x18: mtctr r0 (synthesized as nop — Function::Analyze doesn't
+//         check mtctr specifically)
+//   0x18: bctr                  ; <-- switch-dispatch site
+//   0x1C: label[0] target @ 0x1C: blr
+//   0x20: label[1] target @ 0x20: blr
+//   0x24: label[2] target @ 0x24: blr
+//   0x28: label[3] target @ 0x28: blr
+//   0x2C: (padding)
+//   0x34: default target: blr
+//
+// The walker starts at offset 0, walks to the bctr at 0x18, consults
+// switchMap, and (if populated) pushes all 5 successor blocks (4 labels
+// + default). The walker then reaches each block, processes its `blr`,
+// and terminates. fn.size should cover through 0x34 (the default block's
+// blr).
+//
+// Base address: we use 0x10000 as a synthetic "guest VA" for these
+// tests. Anything > 0 works; 0x10000 is arbitrary.
+
+struct SyntheticSwitch
+{
+    std::vector<uint8_t> bytes;
+    uint32_t baseVa;
+    uint32_t bctrVa;
+    std::vector<uint32_t> labelVas;
+    uint32_t defaultVa;
+};
+
+SyntheticSwitch buildFourCaseSwitch()
+{
+    SyntheticSwitch s;
+    s.baseVa = 0x10000;
+    s.bctrVa = s.baseVa + 0x18;
+    s.defaultVa = s.baseVa + 0x34;
+    s.labelVas = { s.baseVa + 0x1C, s.baseVa + 0x20, s.baseVa + 0x24, s.baseVa + 0x28 };
+
+    // Pre-switch head
+    emitBE(s.bytes, cmplwi_cr6(3, 3));  // cmplwi cr6, r3, 3
+    emitBE(s.bytes, bgt_cr6(0x30));     // bgt cr6, +0x30 (→ 0x34 default)
+    for (int i = 0; i < 4; ++i) emitBE(s.bytes, PPC_NOP);  // filler
+    emitBE(s.bytes, PPC_BCTR);          // 0x18: the bctr
+
+    // Label blocks — each a single blr
+    for (int i = 0; i < 4; ++i) emitBE(s.bytes, PPC_BLR);
+
+    // Padding between the 4 labels (at 0x2C) and default (at 0x34)
+    emitBE(s.bytes, PPC_NOP);
+    emitBE(s.bytes, PPC_NOP);
+
+    // Default block
+    emitBE(s.bytes, PPC_BLR);           // 0x34: default blr
+
+    return s;
+}
+
+// Helper to populate a switchMap entry from a SyntheticSwitch.
+AnalyzerSwitchTableMap buildMap(const SyntheticSwitch& s)
+{
+    AnalyzerSwitchTableMap m;
+    AnalyzerSwitchTable entry;
+    entry.defaultLabel = s.defaultVa;
+    entry.labels = s.labelVas;
+    m.emplace(s.bctrVa, std::move(entry));
+    return m;
+}
+
+int testHappyPath()
+{
+    auto s = buildFourCaseSwitch();
+    auto m = buildMap(s);
+    Function fn = Function::Analyze(s.bytes.data(), s.bytes.size(), s.baseVa, &m);
+
+    // Expected: walker reaches every label + default, all their blocks
+    // get size = 4 (single-blr). fn.size should extend to cover the
+    // default block (0x34 + 4 = 0x38).
+    if (fn.base != s.baseVa) {
+        fprintf(stderr, "[FAIL happy-path] fn.base = 0x%zX, expected 0x%X\n",
+                fn.base, s.baseVa);
+        return 1;
+    }
+    if (fn.size < 0x38) {
+        fprintf(stderr, "[FAIL happy-path] fn.size = 0x%zX, expected >= 0x38 "
+                "(switch labels + default)\n", fn.size);
+        return 1;
+    }
+    fprintf(stderr, "[ok   happy-path] fn.base=0x%zX, fn.size=0x%zX, blocks=%zu\n",
+            fn.base, fn.size, fn.blocks.size());
+    return 0;
+}
+
+int testNullMapSafety()
+{
+    auto s = buildFourCaseSwitch();
+    Function fn = Function::Analyze(s.bytes.data(), s.bytes.size(), s.baseVa,
+                                    /* switchMap = */ nullptr);
+
+    // Expected: walker terminates at bctr without pushing successors,
+    // discontinuity pass erases any blocks past the bctr, fn.size covers
+    // only the pre-switch head (up to and including the bctr at 0x18,
+    // so fn.size >= 0x1C, ≤ 0x20 or so).
+    if (fn.size >= 0x38) {
+        fprintf(stderr, "[FAIL null-map ] fn.size = 0x%zX, expected < 0x38 "
+                "(switchMap=nullptr should use legacy walker)\n", fn.size);
+        return 1;
+    }
+    fprintf(stderr, "[ok   null-map ] fn.base=0x%zX, fn.size=0x%zX "
+            "(legacy walker truncation preserved)\n", fn.base, fn.size);
+    return 0;
+}
+
+int testWrongMapMiss()
+{
+    auto s = buildFourCaseSwitch();
+    // Build a map, but with an entry for a DIFFERENT bctr address.
+    AnalyzerSwitchTableMap m;
+    AnalyzerSwitchTable bogus;
+    bogus.defaultLabel = 0x99999;
+    bogus.labels = { 0xABCDEF };
+    m.emplace(/* bctr VA */ 0xDEADBEEF, std::move(bogus));  // not our bctr
+
+    Function fn = Function::Analyze(s.bytes.data(), s.bytes.size(), s.baseVa, &m);
+
+    // Expected: walker looks up our bctr (0x10018), finds nothing in the
+    // map, falls through to legacy behavior. Same result as null-map.
+    if (fn.size >= 0x38) {
+        fprintf(stderr, "[FAIL wrong-map] fn.size = 0x%zX, expected < 0x38 "
+                "(unrelated switchMap entry should fall through to legacy)\n", fn.size);
+        return 1;
+    }
+    fprintf(stderr, "[ok   wrong-map] fn.base=0x%zX, fn.size=0x%zX "
+            "(unrelated map entry correctly ignored)\n", fn.base, fn.size);
+    return 0;
+}
+
+} // anonymous
+
+int main()
+{
+    int failures = 0;
+    failures += testHappyPath();
+    failures += testNullMapSafety();
+    failures += testWrongMapMiss();
+
+    if (failures) {
+        fprintf(stderr, "\n%d test(s) FAILED\n", failures);
+        return 1;
+    }
+    fprintf(stderr, "\nAll 3 tests PASSED\n");
+    return 0;
+}