[libc++abi][AIX] Add 2 LIT tests for the AIX unwinder

[xingxue]

Summary

This patch creates sub-directory libcxxabi/test/vendor/ibm and adds 2 LIT test cases for the AIX EH under the directory. One tests the restoration of the condition register and the other tests the restoration of vector registers. Both are saved on the stack by the function prologue.

[compnerd]

libcxxabi/test/vendor/ibm/cond_reg_restore.pass.cpp

22

The comment is a bit difficult to parse for me. AIUI, it means to state that the inline assembly forces the prologue/epilogue to save/restore the condition register. That makes sense since the cr2 register is marked as a clobber.

23

Nit: could you use ::: or : : : for the inline assembly parameters please.

libcxxabi/test/vendor/ibm/vec_reg_restore.pass.cpp

40

Why registers 29, 30 and v62, v63? A comment about that would be nice. All four of those are non-volatile registers, which should be restored during the unwinding.

[xingxue]

Hi @compnerd, Thanks very much for your comments! I've made changes accordingly. Please let me know if you have further comments!

libcxxabi/test/vendor/ibm/cond_reg_restore.pass.cpp

22

Sorry about that. Reworded as suggested, thanks!

23

Changed to : : :, thanks!

libcxxabi/test/vendor/ibm/vec_reg_restore.pass.cpp

40

Sorry, will add comments to better describe the code. Thanks!

libcxxabi/test/vendor/ibm/cond_reg_restore.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Check that the condition register is restored properly during unwinding
+// on AIX. Option -O3 is required so that the compiler will re-use the value 
+// in the condition register instead of re-evaluating the condition expression.
+
+// REQUIRES: target=powerpc{{(64)?}}-ibm-aix
+// ADDITIONAL_COMPILE_FLAGS: -O3
+// UNSUPPORTED: no-exceptions
+
+#include <cstdlib>
+#include <cassert>
+
+int __attribute__((noinline)) test2(int i) {
+  // This asm code makes the prologue/epilogue to save/restore the condition
+  // register to/from the stack. The unwinder restores from the stack too.
+  asm volatile("nop" : ::"cr2");
+  if (i > 3) {
+    throw i;
+  }
+  srand(i);
+  return rand() + i;
+}
+
+void __attribute__((noinline)) test(int argc, const char **argv) {
+  int a = atoi(argv[1]);
+  int b = atoi(argv[2]);
+  try {
+    test2(a < b ? argc : b);
+  } catch (int num) {
+    assert(!(a < b));
+  }
+}
+int main(int, char**) {
+  const char *av[]={"a.out", "12", "10"};
+  test(4, av);
+  return 0;
+} 

libcxxabi/test/vendor/ibm/vec_reg_restore.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// Check that the PowerPC vector registers are restored properly during
+// unwinding. Option -mabi=vec-extabi is required to compile the test case.
+
+// REQUIRES: target=powerpc{{(64)?}}-ibm-aix
+// ADDITIONAL_COMPILE_FLAGS: -mabi=vec-extabi
+// UNSUPPORTED: no-exceptions
+
+#include <cstdlib>
+#include <cassert>
+
+int __attribute__((noinline)) test2(int i)
+{
+  if (i > 3)
+    throw i;
+  srand(i);
+  return rand();
+}
+
+int __attribute__((noinline)) test(int i) {
+  // Set vr63=100.
+  asm volatile("li 30, 100\n\t"
+               "mtvsrd 63, 30\n\t"
+               :
+               :
+               :  "v31", "r30");
+  // Set vr62=200.
+  asm volatile("li 29, 200\n\t"
+               "mtvsrd 62, 29\n\t"
+               :
+               :
+               :  "v30", "r29");
+  return test2(i);
+}
+
+// Return the value of vr63 in 'output'.
+#define getFirstValue(output) \
+   asm volatile( "mfvsrd 4, 63\n\t" \
+                 "std 4, %[d]" \
+          : [d] "=rm"(output) \
+          : \
+          : )
+// Return the value of vr62 in 'output'.
+#define getSecondValue(output) \
+   asm volatile( "mfvsrd 4, 62\n\t" \
+                 "std 4, %[d]" \
+          : [d] "=rm"(output) \
+          : \
+          : )
+
+int main(int, char**) {
+  // Set vr63=1.
+  asm volatile("li 30, 1\n\t"
+               "mtvsrd 63, 30\n\t"
+               :
+               :
+               :  "v31", "r30");
+  // Set vr62=1.
+  asm volatile("li 29, 2\n\t"
+               "mtvsrd 62, 29\n\t"
+               :
+               :
+               :  "v30", "r29");
+  long long old;
+  long long old2;
+  getFirstValue(old);
+  getSecondValue(old2);
+  try {
+    test(4);
+  } catch (int num) {
+    long long new_value;
+    long long new_value2;
+    getFirstValue(new_value);
+    getSecondValue(new_value2);
+    assert(old == new_value && old2 == new_value2);
+  }
+  return 0;
+}