[ASan] Really fix zero_page_pc test for PowerPC

[foad]

Summary

As a follow-up to D6167, this patch fixes the test to account for
another difference between PowerPC and x86 systems.

On x86 if you branch to an invalid address, you get a SIGSEGV with PC
set to the invalid address (and si_addr in the siginfo struct also set
to the same address).

On PowerPC, you get a SIGSEGV with PC pointing at the branch
instruction, but si_addr set to the invalid address.

You can see this difference if you run the test case under gdb.

[samsonov]

test/asan/TestCases/zero_page_pc.cc

11–13

Why not

(address|pc) 0x0*4

Also, it would be nice to add a comment with your discovery here.

[foad]

Tweak the regular expression. Add comments.

[samsonov]

LGTM

test/asan/TestCases/zero_page_pc.cc

 // Check that ASan correctly detects SEGV on the zero page.
 // RUN: %clangxx_asan %s -o %t && not %run %t 2>&1 | FileCheck %s
 
 // https://code.google.com/p/address-sanitizer/issues/detail?id=336
 // XFAIL: android
 
 typedef void void_f();
 int main() {
   void_f *func = (void_f *)0x4;
   func();
-  // CHECK: {{AddressSanitizer: SEGV.*(pc.*0004)}}
+  // x86 reports the SEGV with both address=4 and pc=4.
+  // PowerPC64 reports it with address=4 but pc still in main().
+  // CHECK: {{AddressSanitizer: SEGV.*(address|pc) 0x0*4}}
   return 0;
 }