[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

23

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.

24

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

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

41

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

23

Sorry about that. Reworded as suggested, thanks!

24

Changed to : : :, thanks!

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

41

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) {
+  // The inline assembly forces the prologue/epilogue to save/restore the
+  // condition register.
+  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
+
+// AIX does not support the eh_frame section. Instead, the traceback table
+// located at the end of each function provides the information for stack
+// unwinding. Non-volatile GRs, FRs, and VRs clobbered by the function are
+// saved on the stack and the numbers of saved registers are available in the
+// traceback table. Registers are saved from high number to low consecutively,
+// e.g., if n VRs are saved, the order on the stack will be VR63, VR62, ...,
+// VR63-n+1. This test cases checks the unwinder gets to the location of saved
+// VRs which should be 16-byte aligned and restores them correctly based on
+// the number specified in the traceback table. To simplify, only the 2 high
+// numbered VRs are checked. Because PowerPC CPUs do not have instructions to
+// assign a literal value to a VR directly until Power10, the value is
+// assigned to a GR and then from the GR to a VR in the code.
+//
+
+#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) {
+  // Clobber VR63 and VR62 in the function body.
+  // 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);
+    // If the unwinder restores VR63 and VR62 correctly, they should contain
+    // 1 and 2 respectively instead of 100 and 200.
+    assert(old == new_value && old2 == new_value2);
+  }
+  return 0;
+}