[mips] Report correct location when "erroring" about the use of $at when it's not available.

[matheusalmeida]

Summary

This removes the FIXMEs from test/MC/Mips/mips-noat.s.

[dsanders]

LGTM

lib/Target/Mips/AsmParser/MipsAsmParser.cpp

#include "MipsGenAsmMatcher.inc"
   int matchMSA128RegisterName(StringRef Name);
 
   int matchMSA128CtrlRegisterName(StringRef Name);
 
   unsigned getReg(int RC, int RegNo);
 
   unsigned getGPR(int RegNo);
 
-  int getATReg();
+  int getATReg(SMLoc Loc);
 
   bool processInstruction(MCInst &Inst, SMLoc IDLoc,
                           SmallVectorImpl<MCInst> &Instructions);
 
   // Helper function that checks if the value of a vector index is within the
   // boundaries of accepted values for each RegisterKind
   // Example: INSERT.B $w0[n], $1 => 16 > n >= 0
   bool validateMSAIndex(int Val, int RegKind);
if (isImmOpnd) {
     ExprOffset = Inst.getOperand(2).getExpr();
   // All instructions will have the same location.
   TempInst.setLoc(IDLoc);
   // 1st instruction in expansion is LUi. For load instruction we can use
   // the dst register as a temporary if base and dst are different,
   // but for stores we must use $at.
   if (isLoad && (BaseRegNum != RegOpNum))
     TmpRegNum = RegOpNum;
-  else
-    TmpRegNum = getReg(
-      (isGP64()) ? Mips::GPR64RegClassID : Mips::GPR32RegClassID, getATReg());
+  else {
+    int AT = getATReg(IDLoc);
+    // At this point we need AT to perform the expansions and we exit if it is
+    // not available.
+    if (!AT)
+      return;
+    TmpRegNum =
+        getReg((isGP64()) ? Mips::GPR64RegClassID : Mips::GPR32RegClassID, AT);
+  }
 
   TempInst.setOpcode(Mips::LUi);
   TempInst.addOperand(MCOperand::CreateReg(TmpRegNum));
   if (isImmOpnd)
     TempInst.addOperand(MCOperand::CreateImm(HiOffset));
   else {
     if (ExprOffset->getKind() == MCExpr::SymbolRef) {
       SR = static_cast<const MCSymbolRefExpr *>(ExprOffset);

 bool MipsAssemblerOptions::setATReg(unsigned Reg) {
   if (Reg > 31)
     return false;
 
   aTReg = Reg;
   return true;
 }
 
-int MipsAsmParser::getATReg() {
+int MipsAsmParser::getATReg(SMLoc Loc) {
   int AT = Options.getATRegNum();
   if (AT == 0)
-    TokError("Pseudo instruction requires $at, which is not available");
+    reportParseError(Loc,
+                     "Pseudo instruction requires $at, which is not available");
   return AT;
 }
 
 unsigned MipsAsmParser::getReg(int RC, int RegNo) {
   return *(getContext().getRegisterInfo()->getRegClass(RC).begin() + RegNo);
 }
 
 unsigned MipsAsmParser::getGPR(int RegNo) {

test/MC/Mips/mips-noat.s

 # RUN: not llvm-mc %s -triple=mips-unknown-linux 2>%t0 | FileCheck %s
 # RUN: FileCheck -check-prefix=ERROR %s < %t0
 # Check that using the assembler temporary when .set noat is in effect is an error.
 
 # We start with the assembler temporary enabled
 # CHECK-LABEL: test1:
 # CHECK:  lui   $1, 1
 # CHECK:  addu  $1, $1, $2
 # CHECK:  lw    $2, 0($1)
 test1:
         lw      $2, 65536($2)
 
-# FIXME: It would be better if the error pointed at the mnemonic instead of the newline
-# ERROR: mips-noat.s:[[@LINE+4]]:1: error: Pseudo instruction requires $at, which is not available
 test2:
         .set noat
-        lw      $2, 65536($2)
+        lw      $2, 65536($2) # ERROR: mips-noat.s:[[@LINE]]:9: error: Pseudo instruction requires $at, which is not available
+
 
 # Can we switch it back on successfully?
 # CHECK-LABEL: test3:
 # CHECK:  lui   $1, 1
 # CHECK:  addu  $1, $1, $2
 # CHECK:  lw    $2, 0($1)
 test3:
         .set at
         lw      $2, 65536($2)
 
-# FIXME: It would be better if the error pointed at the mnemonic instead of the newline
-# ERROR: mips-noat.s:[[@LINE+4]]:1: error: Pseudo instruction requires $at, which is not available
 test4:
         .set at=$0
-        lw      $2, 65536($2)
-
-# ERROR-NOT: error
+        lw      $2, 65536($2) # ERROR: mips-noat.s:[[@LINE]]:9: error: Pseudo instruction requires $at, which is not available