Return the value of the named CPU register, as it was saved when the current probe point was hit. If the register is 32 bits, it is sign-extended to 64 bits.
For the i386 architecture, the following names are recognized. (name1/name2 indicates that name1 and name2 are alternative names for the same register.) eax/ax, ebp/bp, ebx/bx, ecx/cx, edi/di, edx/dx, eflags/flags, eip/ip, esi/si, esp/sp, orig_eax/orig_ax, xcs/cs, xds/ds, xes/es, xfs/fs, xss/ss.
For the x86_64 architecture, the following names are recognized: 64-bit registers: r8, r9, r10, r11, r12, r13, r14, r15, rax/ax, rbp/bp, rbx/bx, rcx/cx, rdi/di, rdx/dx, rip/ip, rsi/si, rsp/sp; 32-bit registers: eax, ebp, ebx, ecx, edx, edi, edx, eip, esi, esp, flags/eflags, orig_eax; segment registers: xcs/cs, xss/ss.
For powerpc, the following names are recognized: r0, r1, ... r31, nip, msr, orig_gpr3, ctr, link, xer, ccr, softe, trap, dar, dsisr, result.
For s390x, the following names are recognized: r0, r1, ... r15, args, psw.mask, psw.addr, orig_gpr2, ilc, trap.
For AArch64, the following names are recognized: x0, x1, ... x30, fp, lr, sp, pc, and orig_x0.