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    Implement Read/Write constraints on system registers on AArch64 · f9830ec1
    Tamar Christina authored
    This patch adds constraints for read and write only system registers with the
    msr and mrs instructions.  The code will treat having both flags set and none
    set as the same.  These flags add constraints that must be matched up. e.g. a
    system register with a READ only flag set, can only be used with mrs.  If The
    constraint fails a warning is emitted.
    
    Examples of the warnings generated:
    
    test.s: Assembler messages:
    test.s:5: Warning: specified register cannot be written to at operand 1 -- `msr dbgdtrrx_el0,x3'
    test.s:7: Warning: specified register cannot be read from at operand 2 -- `mrs x3,dbgdtrtx_el0'
    test.s:8: Warning: specified register cannot be written to at operand 1 -- `msr midr_el1,x3'
    
    and disassembly notes:
    
    0000000000000000 <main>:
       0:	d5130503 	msr	dbgdtrtx_el0, x3
       4:	d5130503 	msr	dbgdtrtx_el0, x3
       8:	d5330503 	mrs	x3, dbgdtrrx_el0
       c:	d5330503 	mrs	x3, dbgdtrrx_el0
      10:	d5180003 	msr	midr_el1, x3	; note: writing to a read-only register.
    
    Note that because dbgdtrrx_el0 and dbgdtrtx_el0 have the same encoding, during
    disassembly the constraints are use to disambiguate between the two.  An exact
    constraint match is always prefered over partial ones if available.
    
    As always the warnings can be suppressed with -w and also be made errors using
    warnings as errors.
    
    binutils/
    
    	PR binutils/21446
    	* doc/binutils.texi (-M): Document AArch64 options.
    
    gas/
    
    	PR binutils/21446
    	* testsuite/gas/aarch64/illegal-sysreg-2.s: Fix pmbidr_el1 test.
    	* testsuite/gas/aarch64/illegal-sysreg-2.l: Likewise.
    	* testsuite/gas/aarch64/illegal-sysreg-2.d: Likewise.
    	* testsuite/gas/aarch64/sysreg-diagnostic.s: New.
    	* testsuite/gas/aarch64/sysreg-diagnostic.l: New.
    	* testsuite/gas/aarch64/sysreg-diagnostic.d: New.
    
    include/
    
    	PR binutils/21446
    	* opcode/aarch64.h (F_SYS_READ, F_SYS_WRITE): New.
    
    opcodes/
    
    	PR binutils/21446
    	* aarch64-asm.c (opintl.h): Include.
    	(aarch64_ins_sysreg): Enforce read/write constraints.
    	* aarch64-dis.c (aarch64_ext_sysreg): Likewise.
    	* aarch64-opc.h (F_DEPRECATED, F_ARCHEXT, F_HASXT): Moved here.
    	(F_REG_READ, F_REG_WRITE): New.
    	* aarch64-opc.c (aarch64_print_operand): Generate notes for
    	AARCH64_OPND_SYSREG.
    	(F_DEPRECATED, F_ARCHEXT, F_HASXT): Move to aarch64-opc.h.
    	(aarch64_sys_regs): Add constraints to currentel, midr_el1, ctr_el0,
    	mpidr_el1, revidr_el1, aidr_el1, dczid_el0, id_dfr0_el1, id_pfr0_el1,
    	id_pfr1_el1, id_afr0_el1, id_mmfr0_el1, id_mmfr1_el1, id_mmfr2_el1,
    	id_mmfr3_el1, id_mmfr4_el1, id_isar0_el1, id_isar1_el1, id_isar2_el1,
    	id_isar3_el1, id_isar4_el1, id_isar5_el1, mvfr0_el1, mvfr1_el1,
    	mvfr2_el1, ccsidr_el1, id_aa64pfr0_el1, id_aa64pfr1_el1,
    	id_aa64dfr0_el1, id_aa64dfr1_el1, id_aa64isar0_el1, id_aa64isar1_el1,
    	id_aa64mmfr0_el1, id_aa64mmfr1_el1, id_aa64mmfr2_el1, id_aa64afr0_el1,
    	id_aa64afr0_el1, id_aa64afr1_el1, id_aa64zfr0_el1, clidr_el1,
    	csselr_el1, vsesr_el2, erridr_el1, erxfr_el1, rvbar_el1, rvbar_el2,
    	rvbar_el3, isr_el1, tpidrro_el0, cntfrq_el0, cntpct_el0, cntvct_el0,
    	mdccsr_el0, dbgdtrrx_el0, dbgdtrtx_el0, osdtrrx_el1, osdtrtx_el1,
    	mdrar_el1, oslar_el1, oslsr_el1, dbgauthstatus_el1, pmbidr_el1,
    	pmsidr_el1, pmswinc_el0, pmceid0_el0, pmceid1_el0.
    	* aarch64-tbl.h (aarch64_opcode_table): Add constraints to
    	msr (F_SYS_WRITE), mrs (F_SYS_READ).
    f9830ec1
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