[LLDB][NFC] Fix suspicious bitwise expression in PrintBTEntry()

[fixathon]

Summary

Current application of bitwise-OR to a binary mask always results in True, which seems
inconsistent with the intent of the statement, a likely typo.

[hawkinsw]

lldb/tools/intel-features/intel-mpx/cli-wrapper-mpxtable.cpp

66

According to https://en.cppreference.com/w/cpp/language/operator_precedence, I would read the left operand of the && as

1. The == has higher precedence than || so, b = (lbound == one_compl64)
2. b || one_cmpl32

which does not seem like what the original author intended. I absolutely think that the fix is correct, but I just wanted to get everyone's feedback on whether this seems like more than just a "suspicious bitwise expression" (and more like a "mistaken bitwise expression").

All that said, I could be completely, 100% wrong. And, if I am, feel free to ignore me!

[DavidSpickett]

The original change was https://reviews.llvm.org/D29078. Are you able to run the tests with this applied?

lldb/tools/intel-features/intel-mpx/cli-wrapper-mpxtable.cpp

66

The corrected code also makes sense given that MPX is some kind of memory protection across ranges.

If ((lbound == one_cmpl64 || lbound == one_cmpl32) && ubound == 0) is true then upper bound < lower bound making an invalid range. Which is what I'd expect for some default/uninitialised state (especially if zero size ranges are allowed, so upper == 0 and lower == 0 couldn't be used).

[hawkinsw]

lldb/tools/intel-features/intel-mpx/cli-wrapper-mpxtable.cpp

66

@DavidSpickett I think that you and I are saying the same thing, right? We are both saying that the corrected code looks much "better" than the original?

Will

[DavidSpickett]

lldb/tools/intel-features/intel-mpx/cli-wrapper-mpxtable.cpp

66

We are both saying that the corrected code looks much "better" than the original?

Yes.

whether this seems like more than just a "suspicious bitwise expression" (and more like a "mistaken bitwise expression").

Definitely a mistake that needs correcting.

[DavidSpickett]

lldb/tools/intel-features/intel-mpx/cli-wrapper-mpxtable.cpp

66

(I think "suspicious bitwise expression" is what the static analyser would call it just because it can't be 100% sure it is wrong)

lldb/tools/intel-features/intel-mpx/cli-wrapper-mpxtable.cpp

 };
 
 static void PrintBTEntry(lldb::addr_t lbound, lldb::addr_t ubound,
                          uint64_t value, uint64_t meta,
                          lldb::SBCommandReturnObject &result) {
   const lldb::addr_t one_cmpl64 = ~((lldb::addr_t)0);
   const lldb::addr_t one_cmpl32 = ~((uint32_t)0);
 
-  if ((lbound == one_cmpl64 || one_cmpl32) && ubound == 0) {
+  if ((lbound == one_cmpl64 || lbound == one_cmpl32) && ubound == 0) {
     result.Printf("Null bounds on map: pointer value = 0x%" PRIu64 "\n", value);
   } else {
     result.Printf("    lbound = 0x%" PRIu64 ",", lbound);
     result.Printf(" ubound = 0x%" PRIu64 , ubound);
     result.Printf(" (pointer value = 0x%" PRIu64 ",", value);
     result.Printf(" metadata = 0x%" PRIu64 ")\n", meta);
   }
 }