[ARM] Don't print "Requires NEON" error message for M-profile

[avieira]

Summary

Hi,

This patch makes the disassembler not print the "instruction requires:
NEON" message when compiling for M-profile as there are no NEON
extensions for M-profile.

Regards,
Andre

[samparker]

I would of thought it more useful to give a detailed error message, but it seems that is not the practise, so LGTM, thanks.

[rengolin]

For M-class, "invalid instruction" is indeed more accurate than requires NEON. We don't want people to think they can add "-mfpu=neon" or ".fpu neon" to an M-class to force assembling that code.

To have a better handling than this, we'd have to error out earlier saying M-class doesn't have NEON, which probably needs more knowledge than that piece of code has... LGTM too, for now.

[olista01]

To have a better handling than this, we'd have to error out earlier saying M-class doesn't have NEON, which probably needs more knowledge than that piece of code has...

We actually could do that here, the code immediately following the change is building the string to be printed, so we could just return a special "M-class doesn't have NEON" string. However, that would probably be a special-case too far, so I think this is fine as it is.

[rengolin]

In D43125#1004879, @olista01 wrote:

We actually could do that here, the code immediately following the change is building the string to be printed, so we could just return a special "M-class doesn't have NEON" string. However, that would probably be a special-case too far, so I think this is fine as it is.

Yeah, this would have to be a table-gen driven kind of change to cover all cases. For another patch.

llvm/trunk/lib/Target/ARM/AsmParser/ARMAsmParser.cpp

case NearMissInfo::NearMissFeature: {
           (MissingFeatures & ~Feature_IsARM))
         break;
       if (!isThumb() && (MissingFeatures & Feature_IsThumb) &&
           (MissingFeatures & ~Feature_IsThumb))
         break;
       if (!isThumb() && (MissingFeatures & Feature_IsThumb2) &&
           (MissingFeatures & ~(Feature_IsThumb2 | Feature_IsThumb)))
         break;
+      if (isMClass() && (MissingFeatures & Feature_HasNEON))
+        break;
 
       NearMissMessage Message;
       Message.Loc = IDLoc;
       raw_svector_ostream OS(Message.Message);
 
       OS << "instruction requires:";
       uint64_t Mask = 1;
       for (unsigned MaskPos = 0; MaskPos < (sizeof(MissingFeatures) * 8 - 1);

llvm/trunk/test/MC/ARM/vfp4.s

 @ ARM: vfma.f32 d16, d18, d17 @ encoding: [0xb1,0x0c,0x42,0xf2]
 @ THUMB: vfma.f32 d16, d18, d17 @ encoding: [0x42,0xef,0xb1,0x0c]
 @ THUMB_V7EM-ERRORS: error: invalid instruction
 @ THUMB_V7EM-ERRORS-NEXT: vfma.f32 d16, d18, d17
 vfma.f32 d16, d18, d17
 
 @ ARM: vfma.f32 q2, q4, q0 @ encoding: [0x50,0x4c,0x08,0xf2]
 @ THUMB: vfma.f32  q2, q4, q0 @ encoding: [0x08,0xef,0x50,0x4c]
-@ THUMB_V7EM-ERRORS: error: instruction requires: NEON
+@ THUMB_V7EM-ERRORS: error: invalid instruction
 @ THUMB_V7EM-ERRORS-NEXT: vfma.f32 q2, q4, q0
 vfma.f32 q2, q4, q0
 
 @ ARM: vfnma.f64 d16, d18, d17 @ encoding: [0xe1,0x0b,0xd2,0xee]
 @ THUMB: vfnma.f64 d16, d18, d17 @ encoding: [0xd2,0xee,0xe1,0x0b]
 @ THUMB_V7EM-ERRORS: error: invalid instruction
 @ THUMB_V7EM-ERRORS-NEXT: vfnma.f64 d16, d18, d17
 vfnma.f64 d16, d18, d17

 @ ARM: vfms.f32 d16, d18, d17 @ encoding: [0xb1,0x0c,0x62,0xf2]
 @ THUMB: vfms.f32 d16, d18, d17 @ encoding: [0x62,0xef,0xb1,0x0c]
 @ THUMB_V7EM-ERRORS: error: invalid instruction
 @ THUMB_V7EM-ERRORS-NEXT: vfms.f32 d16, d18, d17
 vfms.f32 d16, d18, d17
 
 @ ARM: vfms.f32 q2, q4, q0 @ encoding: [0x50,0x4c,0x28,0xf2]
 @ THUMB: vfms.f32  q2, q4, q0 @ encoding: [0x28,0xef,0x50,0x4c]
-@ THUMB_V7EM-ERRORS: error: instruction requires: NEON
+@ THUMB_V7EM-ERRORS: error: invalid instruction
 @ THUMB_V7EM-ERRORS-NEXT: vfms.f32 q2, q4, q0
 vfms.f32 q2, q4, q0
 
 @ ARM: vfnms.f64 d16, d18, d17 @ encoding: [0xa1,0x0b,0xd2,0xee]
 @ THUMB: vfnms.f64 d16, d18, d17 @ encoding: [0xd2,0xee,0xa1,0x0b]
 @ THUMB_V7EM-ERRORS: error: invalid instruction
 @ THUMB_V7EM-ERRORS-NEXT: vfnms.f64 d16, d18, d17
 vfnms.f64 d16, d18, d17
 
 @ ARM: vfnms.f32 s2, s4, s0 @ encoding: [0x00,0x1a,0x92,0xee]
 @ THUMB: vfnms.f32 s2, s4, s0 @ encoding: [0x92,0xee,0x00,0x1a]
 @ THUMB_V7EM: vfnms.f32 s2, s4, s0 @ encoding: [0x92,0xee,0x00,0x1a]
 vfnms.f32 s2, s4, s0