[LoongArch] Report error in AsmParser when rd == rk or rd == rj for AM* instructions

[SixWeining]

Summary

Do this check because the ISA manual says (edited from the original translation):

If the AM* instruction has its rd == rj, an Instruction Non-defined Exception will be triggered when the instruction is executed.

If the AM* instruction has its rd == rk, the execution result is unpredictable. It is software's responsibility to avoid this situation.

Note that binutils does the same check except when rd == r0 but this
is undocumented.

[xen0n]

The changes look good but unfortunately the manual (!) is poorly translated in this case. Quoting verbatim, while still comprehensible, is an eyesore that is better fixed.

Here's my take:

Do this check because the ISA manual says (edited from the original translation):

> If the AM* instruction has its rd == rj, an Instruction Non-defined Exception will be triggered when the instruction is executed.
>
> If the AM* instruction has its rd == rk, the execution result is unpredictable. It is software's responsibility to avoid this situation.

What do you think?

[SixWeining]

In D136076#3863830, @xen0n wrote:

The changes look good but unfortunately the manual (!) is poorly translated in this case. Quoting verbatim, while still comprehensible, is an eyesore that is better fixed.

Here's my take:

Do this check because the ISA manual says (edited from the original translation):

> If the AM* instruction has its rd == rj, an Instruction Non-defined Exception will be triggered when the instruction is executed.
>
> If the AM* instruction has its rd == rk, the execution result is unpredictable. It is software's responsibility to avoid this situation.

What do you think?

That sounds good. I will take. Thanks.

llvm/lib/Target/LoongArch/AsmParser/LoongArchAsmParser.cpp

#include "LoongArchGenAsmMatcher.inc"
 
   bool parseOperand(OperandVector &Operands, StringRef Mnemonic);
 
 public:
   enum LoongArchMatchResultTy {
     Match_Dummy = FIRST_TARGET_MATCH_RESULT_TY,
     Match_RequiresMsbNotLessThanLsb,
     Match_RequiresOpnd2NotR0R1,
+    Match_RequiresAMORdDifferRkRj,
 #define GET_OPERAND_DIAGNOSTIC_TYPES
 #include "LoongArchGenAsmMatcher.inc"
 #undef GET_OPERAND_DIAGNOSTIC_TYPES
   };
 
   static bool classifySymbolRef(const MCExpr *Expr,
                                 LoongArchMCExpr::VariantKind &Kind);
 
bool LoongArchAsmParser::processInstruction(MCInst &Inst, SMLoc IDLoc,
                                             OperandVector &Operands,
                                             MCStreamer &Out) {
   Inst.setLoc(IDLoc);
   Out.emitInstruction(Inst, getSTI());
   return false;
 }
 
 unsigned LoongArchAsmParser::checkTargetMatchPredicate(MCInst &Inst) {
-  switch (Inst.getOpcode()) {
+  unsigned Opc = Inst.getOpcode();
+  switch (Opc) {
   default:
+    if (Opc >= LoongArch::AMADD_D && Opc <= LoongArch::AMXOR_W) {
+      unsigned Rd = Inst.getOperand(0).getReg();
+      unsigned Rk = Inst.getOperand(1).getReg();
+      unsigned Rj = Inst.getOperand(2).getReg();
+      if (Rd == Rk || Rd == Rj)
+        return Match_RequiresAMORdDifferRkRj;
+    }
     break;
   case LoongArch::CSRXCHG: {
     unsigned Rj = Inst.getOperand(2).getReg();
     if (Rj == LoongArch::R0 || Rj == LoongArch::R1)
       return Match_RequiresOpnd2NotR0R1;
     return Match_Success;
   }
   case LoongArch::BSTRINS_W:
default:
     break;
   case Match_RequiresMsbNotLessThanLsb: {
     SMLoc ErrorStart = Operands[3]->getStartLoc();
     return Error(ErrorStart, "msb is less than lsb",
                  SMRange(ErrorStart, Operands[4]->getEndLoc()));
   }
   case Match_RequiresOpnd2NotR0R1:
     return Error(Operands[2]->getStartLoc(), "must not be $r0 or $r1");
+  case Match_RequiresAMORdDifferRkRj:
+    return Error(Operands[1]->getStartLoc(),
+                 "$rd must be different from both $rk and $rj");
   case Match_InvalidUImm2:
     return generateImmOutOfRangeError(Operands, ErrorInfo, /*Lower=*/0,
                                       /*Upper=*/(1 << 2) - 1);
   case Match_InvalidUImm2plus1:
     return generateImmOutOfRangeError(Operands, ErrorInfo, /*Lower=*/1,
                                       /*Upper=*/(1 << 2));
   case Match_InvalidUImm3:
     return generateImmOutOfRangeError(Operands, ErrorInfo, /*Lower=*/0,

llvm/test/MC/LoongArch/Basic/Integer/invalid64.s

 ## msbd < lsbd
 # CHECK: :[[#@LINE+1]]:21: error: msb is less than lsb
 bstrins.d $a0, $a0, 1, 2
 # CHECK:            ^~~~
 
 # CHECK: :[[#@LINE+1]]:22: error: msb is less than lsb
 bstrpick.d $a0, $a0, 32, 63
 # CHECK:             ^~~~~~
+
+# CHECK: :[[#@LINE+1]]:10: error: $rd must be different from both $rk and $rj
+amadd.d $zero, $zero, $zero
+# CHECK: :[[#@LINE+1]]:10: error: $rd must be different from both $rk and $rj
+ammin.w $zero, $zero, $a0
+# CHECK: :[[#@LINE+1]]:10: error: $rd must be different from both $rk and $rj
+amxor.w $zero, $a0, $zero
+
+# CHECK: :[[#@LINE+1]]:10: error: $rd must be different from both $rk and $rj
+amadd.d $a0, $a0, $a0
+# CHECK: :[[#@LINE+1]]:10: error: $rd must be different from both $rk and $rj
+ammin.w $a0, $a0, $a1
+# CHECK: :[[#@LINE+1]]:10: error: $rd must be different from both $rk and $rj
+amxor.w $a0, $a1, $a0