Kernel+LibC: Modify aarch64's __mcontext to store registers in an array

This commit also removes the unnecessary ifdefs from
sys/arch/aarch64/regs.h. Contributed by konrad, thanks for that.

Kernel/Arch/aarch64/mcontext.h

@@ -13,37 +13,7 @@ extern "C" {
 #endif
 
 struct __attribute__((packed)) __mcontext {
-    uint64_t r0;
-    uint64_t r1;
-    uint64_t r2;
-    uint64_t r3;
-    uint64_t r4;
-    uint64_t r5;
-    uint64_t r6;
-    uint64_t r7;
-    uint64_t r8;
-    uint64_t r9;
-    uint64_t r10;
-    uint64_t r11;
-    uint64_t r12;
-    uint64_t r13;
-    uint64_t r14;
-    uint64_t r15;
-    uint64_t r16;
-    uint64_t r17;
-    uint64_t r18;
-    uint64_t r19;
-    uint64_t r20;
-    uint64_t r21;
-    uint64_t r22;
-    uint64_t r23;
-    uint64_t r24;
-    uint64_t r25;
-    uint64_t r26;
-    uint64_t r27;
-    uint64_t r28;
-    uint64_t r29;
-    uint64_t r30;
+    uint64_t x[31];
     uint64_t sp;
     uint64_t pc;
 };

Userland/Libraries/LibC/sys/arch/aarch64/regs.h

@@ -21,46 +21,22 @@ struct [[gnu::packed]] PtraceRegisters : public __mcontext {
 #    if defined(__cplusplus) && defined(__cpp_concepts)
     FlatPtr ip() const
     {
-#        if ARCH(X86_64)
-        return rip;
-#        elif ARCH(AARCH64)
         return pc;
-#        else
-#            error Unknown architecture
-#        endif
     }
 
     void set_ip(FlatPtr ip)
     {
-#        if ARCH(X86_64)
-        rip = ip;
-#        elif ARCH(AARCH64)
         pc = ip;
-#        else
-#            error Unknown architecture
-#        endif
     }
 
     FlatPtr bp() const
     {
-#        if ARCH(X86_64)
-        return rbp;
-#        elif ARCH(AARCH64)
-        return r29;
-#        else
-#            error Unknown architecture
-#        endif
+        return x[29];
     }
 
     void set_bp(FlatPtr bp)
     {
-#        if ARCH(X86_64)
-        rbp = bp;
-#        elif ARCH(AARCH64)
-        r29 = bp;
-#        else
-#            error Unknown architecture
-#        endif
+        x[29] = bp;
     }
 #    endif
 };