[Hexagon] Disallow using the same register for Vy/Vx in vdeal/vshuff

[quic-akaryaki]

Summary

Non-assignment forms of vshuff and vdeal use the first two registers
(Vy, Vx) as both inputs and outputs. It is not valid to use the same
register for both Vy and Vx. The double-write error was not detected
previously because of a special case, which is not actually necessary.

llvm/lib/Target/Hexagon/MCTargetDesc/HexagonMCChecker.cpp

         // TODO: relies on the impossibility of a current and a temporary loads
         // in the same packet.
         TmpDefs.insert(*SRI);
-      else if (i <= 1 && HexagonMCInstrInfo::hasNewValue2(MCII, MCI))
-        // vshuff(Vx, Vy, Rx) <- Vx(0) and Vy(1) are both source and
-        // destination registers with this instruction. same for vdeal(Vx,Vy,Rx)
-        Uses.insert(*SRI);
       else if (!IgnoreTmpDst)
         Defs[*SRI].insert(PredSense(PredReg, isTrue));
     }

llvm/test/MC/Hexagon/PacketRules/hvx_vshuff_vdeal.s

+# RUN: not llvm-mc -arch=hexagon -mv65 -mhvx -filetype=obj -o 1.o %s 2>&1 | FileCheck --implicit-check-not=error %s
+
+{ v1 = v2; vshuff(v1,v3,r0) }
+# CHECK: error: register `V1' modified more than once
+
+{ v4 = v3; vdeal(v6,v4,r0) }
+# CHECK: error: register `V4' modified more than once

llvm/test/MC/Hexagon/PacketRules/hvx_vshuff_vdeal_dup.s

+# RUN: not llvm-mc -arch=hexagon -mv65 -mhvx -filetype=obj %s 2>&1 | FileCheck %s
+
+{ vshuff(v0,v0,r0) }
+# CHECK: error: register `V0' modified more than once
+
+{ vdeal(v1,v1,r0) }
+# CHECK: error: register `V1' modified more than once

llvm/test/MC/Hexagon/extensions/v67_hvx.s

 
 //  V6_vdeal
 //  vdeal(Vy32,Vx32,Rt32)
-    vdeal(v0,v0,r0)
-# CHECK-NEXT: 19e0e040 { vdeal(v0,v0,r0) }
+    vdeal(v0,v1,r0)
+# CHECK-NEXT: 19e0e041 { vdeal(v0,v1,r0) }
 
 //  V6_vdealb
 //  Vd32.b=vdeal(Vu32.b)

 
 //  V6_vshuff
 //  vshuff(Vy32,Vx32,Rt32)
-    vshuff(v0,v0,r0)
-# CHECK-NEXT: 19e0e020 { vshuff(v0,v0,r0) }
+    vshuff(v0,v1,r0)
+# CHECK-NEXT: 19e0e021 { vshuff(v0,v1,r0) }
 
 //  V6_vshuffb
 //  Vd32.b=vshuff(Vu32.b)