ARM: improved assembler diagnostics for missing CPU features.

When an instruction match is found, but the subtarget features it
requires are not available (missing floating point unit, or thumb vs arm
mode, for example), issue a diagnostic that identifies what the feature
mismatch is.

rdar://11257547

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@155499 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 42 insertions, 23 deletions

diff --git a/lib/Target/ARM/ARMInstrInfo.td b/lib/Target/ARM/ARMInstrInfo.td
index 6b874b2..633b53f 100644
--- a/lib/Target/ARM/ARMInstrInfo.td
+++ b/lib/Target/ARM/ARMInstrInfo.td
@@ -161,53 +161,59 @@ def ARMbfi           : SDNode<"ARMISD::BFI", SDT_ARMBFI>;
 // ARM Instruction Predicate Definitions.
 //
 def HasV4T           : Predicate<"Subtarget->hasV4TOps()">,
-                                 AssemblerPredicate<"HasV4TOps">;
+                                 AssemblerPredicate<"HasV4TOps", "armv4t">;
 def NoV4T            : Predicate<"!Subtarget->hasV4TOps()">;
 def HasV5T           : Predicate<"Subtarget->hasV5TOps()">;
 def HasV5TE          : Predicate<"Subtarget->hasV5TEOps()">,
-                                 AssemblerPredicate<"HasV5TEOps">;
+                                 AssemblerPredicate<"HasV5TEOps", "armv5te">;
 def HasV6            : Predicate<"Subtarget->hasV6Ops()">,
-                                 AssemblerPredicate<"HasV6Ops">;
+                                 AssemblerPredicate<"HasV6Ops", "armv6">;
 def NoV6             : Predicate<"!Subtarget->hasV6Ops()">;
 def HasV6T2          : Predicate<"Subtarget->hasV6T2Ops()">,
-                                 AssemblerPredicate<"HasV6T2Ops">;
+                                 AssemblerPredicate<"HasV6T2Ops", "armv6t2">;
 def NoV6T2           : Predicate<"!Subtarget->hasV6T2Ops()">;
 def HasV7            : Predicate<"Subtarget->hasV7Ops()">,
-                                 AssemblerPredicate<"HasV7Ops">;
+                                 AssemblerPredicate<"HasV7Ops", "armv7">;
 def NoVFP            : Predicate<"!Subtarget->hasVFP2()">;
 def HasVFP2          : Predicate<"Subtarget->hasVFP2()">,
-                                 AssemblerPredicate<"FeatureVFP2">;
+                                 AssemblerPredicate<"FeatureVFP2", "VFP2">;
 def HasVFP3          : Predicate<"Subtarget->hasVFP3()">,
-                                 AssemblerPredicate<"FeatureVFP3">;
+                                 AssemblerPredicate<"FeatureVFP3", "VFP3">;
 def HasVFP4          : Predicate<"Subtarget->hasVFP4()">,
-                                 AssemblerPredicate<"FeatureVFP4">;
+                                 AssemblerPredicate<"FeatureVFP4", "VFP4">;
 def HasNEON          : Predicate<"Subtarget->hasNEON()">,
-                                 AssemblerPredicate<"FeatureNEON">;
+                                 AssemblerPredicate<"FeatureNEON", "NEON">;
 def HasFP16          : Predicate<"Subtarget->hasFP16()">,
-                                 AssemblerPredicate<"FeatureFP16">;
+                                 AssemblerPredicate<"FeatureFP16","half-float">;
 def HasDivide        : Predicate<"Subtarget->hasDivide()">,
-                                 AssemblerPredicate<"FeatureHWDiv">;
+                                 AssemblerPredicate<"FeatureHWDiv", "divide">;
 def HasT2ExtractPack : Predicate<"Subtarget->hasT2ExtractPack()">,
-                                 AssemblerPredicate<"FeatureT2XtPk">;
+                                 AssemblerPredicate<"FeatureT2XtPk",
+                                                     "pack/extract">;
 def HasThumb2DSP     : Predicate<"Subtarget->hasThumb2DSP()">,
-                                 AssemblerPredicate<"FeatureDSPThumb2">;
+                                 AssemblerPredicate<"FeatureDSPThumb2",
+                                                    "thumb2-dsp">;
 def HasDB            : Predicate<"Subtarget->hasDataBarrier()">,
-                                 AssemblerPredicate<"FeatureDB">;
+                                 AssemblerPredicate<"FeatureDB",
+                                                    "data-barriers">;
 def HasMP            : Predicate<"Subtarget->hasMPExtension()">,
-                                 AssemblerPredicate<"FeatureMP">;
+                                 AssemblerPredicate<"FeatureMP",
+                                                    "mp-extensions">;
 def UseNEONForFP     : Predicate<"Subtarget->useNEONForSinglePrecisionFP()">;
 def DontUseNEONForFP : Predicate<"!Subtarget->useNEONForSinglePrecisionFP()">;
 def IsThumb          : Predicate<"Subtarget->isThumb()">,
-                                 AssemblerPredicate<"ModeThumb">;
+                                 AssemblerPredicate<"ModeThumb", "thumb">;
 def IsThumb1Only     : Predicate<"Subtarget->isThumb1Only()">;
 def IsThumb2         : Predicate<"Subtarget->isThumb2()">,
-                                 AssemblerPredicate<"ModeThumb,FeatureThumb2">;
+                                 AssemblerPredicate<"ModeThumb,FeatureThumb2",
+                                                    "thumb2">;
 def IsMClass         : Predicate<"Subtarget->isMClass()">,
-                                 AssemblerPredicate<"FeatureMClass">;
+                                 AssemblerPredicate<"FeatureMClass", "armv7m">;
 def IsARClass        : Predicate<"!Subtarget->isMClass()">,
-                                 AssemblerPredicate<"!FeatureMClass">;
+                                 AssemblerPredicate<"!FeatureMClass",
+                                                    "armv7a/r">;
 def IsARM            : Predicate<"!Subtarget->isThumb()">,
-                                 AssemblerPredicate<"!ModeThumb">;
+                                 AssemblerPredicate<"!ModeThumb", "arm-mode">;
 def IsIOS            : Predicate<"Subtarget->isTargetIOS()">;
 def IsNotIOS         : Predicate<"!Subtarget->isTargetIOS()">;
 def IsNaCl           : Predicate<"Subtarget->isTargetNaCl()">;
diff --git a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
index 2c53e3f..cbd9bdb 100644
--- a/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
+++ b/lib/Target/ARM/AsmParser/ARMAsmParser.cpp
@@ -7277,6 +7277,7 @@ unsigned ARMAsmParser::checkTargetMatchPredicate(MCInst &Inst) {
   return Match_Success;
 }
 
+static const char *getSubtargetFeatureName(unsigned Val);
 bool ARMAsmParser::
 MatchAndEmitInstruction(SMLoc IDLoc,
                         SmallVectorImpl<MCParsedAsmOperand*> &Operands,
@@ -7317,9 +7318,21 @@ MatchAndEmitInstruction(SMLoc IDLoc,
     Inst.setLoc(IDLoc);
     Out.EmitInstruction(Inst);
     return false;
-  case Match_MissingFeature:
-    Error(IDLoc, "instruction requires a CPU feature not currently enabled");
-    return true;
+  case Match_MissingFeature: {
+    assert(ErrorInfo && "Unknown missing feature!");
+    // Special case the error message for the very common case where only
+    // a single subtarget feature is missing (Thumb vs. ARM, e.g.).
+    std::string Msg = "instruction requires:";
+    unsigned Mask = 1;
+    for (unsigned i = 0; i < (sizeof(ErrorInfo)*8-1); ++i) {
+      if (ErrorInfo & Mask) {
+        Msg += " ";
+        Msg += getSubtargetFeatureName(ErrorInfo & Mask);
+      }
+      Mask <<= 1;
+    }
+    return Error(IDLoc, Msg);
+  }
   case Match_InvalidOperand: {
     SMLoc ErrorLoc = IDLoc;
     if (ErrorInfo != ~0U) {