[PowerPC] Improve error message on MASSV pass

[masoud.ataei]

Summary

Problem:
If user add -mno-altivec along with -mllvm -vector-library=MASSV regardless of compiling P8 or P9 (or other targets), they will get confusing message.

Solution:
Updated the error message to mention vectorization is needed be enable when using MASSV pass.

[bmahjour]

llvm/lib/Target/PowerPC/PPCLowerMASSVEntries.cpp

86

what about Power 10? should it say "Power8 and above" or "Power8 or later"?

[masoud.ataei]

llvm/lib/Target/PowerPC/PPCLowerMASSVEntries.cpp

86

Currently there is no Power10 specific entry on Linux MASS library (there are on AIX). So, if you use -mcpu=pwr10 you are actually getting P9 specific functions (like __xl_expd2_P9).

Do you still think the message should say "Power8 and above"?

[bmahjour]

llvm/lib/Target/PowerPC/PPCLowerMASSVEntries.cpp

86

Sure, but MASSV is still supported on P10. The fact that we resolve to p9 entries in some cases is an implementation detail that is not relevant to the purpose of this message. I'd prefer "Power8 and later".

[xgupta]

Seems patch is committed in https://reviews.llvm.org/rGee2068b30ecf297c004c06eedd7e1063c67a279c, revision should be close now?

[masoud.ataei]

In D106091#2896031, @xgupta wrote:

Seems patch is committed in https://reviews.llvm.org/rGee2068b30ecf297c004c06eedd7e1063c67a279c, revision should be close now?

Yes, thanks for closing it.

[bmahjour]

In D106091#2896723, @masoud.ataei wrote:

In D106091#2896031, @xgupta wrote:

Seems patch is committed in https://reviews.llvm.org/rGee2068b30ecf297c004c06eedd7e1063c67a279c, revision should be close now?

Yes, thanks for closing it.

The tools that automatically close reviews are very particular about the format of the commit message. In this case, there is an extra space at the beginning of the line that's meant to start with Differential Revision:, that's probably why auto-close didn't work.

llvm/lib/Target/PowerPC/PPCLowerMASSVEntries.cpp

   // Assume Power8 when Subtarget is unavailable.
   if (!Subtarget)
     return "P8";
   if (Subtarget->hasP9Vector())
     return "P9";
   if (Subtarget->hasP8Vector())
     return "P8";
 
-  report_fatal_error("Unsupported Subtarget: MASSV is supported only on "
-                     "Power8 and Power9 subtargets.");
+  report_fatal_error(
+      "-vector-library=MASSV option is supported only on Power8 and later "
+      "subtargets when vectorization is not disabled.");
 }
 
 /// Creates PowerPC subtarget-specific name corresponding to the specified
 /// generic MASSV function, and the PowerPC subtarget.
 std::string
 PPCLowerMASSVEntries::createMASSVFuncName(Function &Func,
                                           const PPCSubtarget *Subtarget) {
   StringRef Suffix = getCPUSuffix(Subtarget);