On 31/03/17 09:34, Richard Sandiford wrote:
> The movsi and movdi constraints allowed the source to be any
> absolute symbolic expression ("S"). That's OK for operands that
> have already been vetted by the aarch64_mov_operand predicate but
> causes problems if the register allocator substitutes an equivalence
> (the usual "the constraints can't accept more than the predicates"
> restriction).
>
> Although all other uses of "S" in the backend are redundant and could
> in principle be removed, "S" itself is a publicly-documented constraint
> and so we'd have to keep its definition. This patch therefore adds a
> new "Usa" constraint for legitimate absolute address operands.
>
> I saw this for a large testcase in which an equivalence was used
> for a label_ref jump table. It's not something that can be cut
> down easily or that would give a robust regression test.
>
> I don't think this is a regression, so maybe we don't want it for GCC 7.
>
> Tested on aarch64-linux-gnu. OK to install?
>
OK.
R.
> Thanks,
> Richard
>
>
> gcc/
> * config/aarch64/constraints.md (Usa): New constraint.
> * config/aarch64/aarch64.md (*movsi_aarch64, *movdi_aarch64): Use it.
>
> diff --git a/gcc/config/aarch64/aarch64.md b/gcc/config/aarch64/aarch64.md
> index 3717edf..260bd64 100644
> --- a/gcc/config/aarch64/aarch64.md
> +++ b/gcc/config/aarch64/aarch64.md
> @@ -1074,7 +1074,7 @@
>
> (define_insn_and_split "*movsi_aarch64"
> [(set (match_operand:SI 0 "nonimmediate_operand" "=r,k,r,r,r,r ,r,*w,m,
> m,r,r ,*w, r,*w")
> - (match_operand:SI 1 "aarch64_mov_operand" " r,r,k,M,n,Dv,m,
> m,rZ,*w,S,Ush,rZ,*w,*w"))]
> + (match_operand:SI 1 "aarch64_mov_operand" " r,r,k,M,n,Dv,m,
> m,rZ,*w,Usa,Ush,rZ,*w,*w"))]
> "(register_operand (operands[0], SImode)
> || aarch64_reg_or_zero (operands[1], SImode))"
> "@
> @@ -1108,7 +1108,7 @@
>
> (define_insn_and_split "*movdi_aarch64"
> [(set (match_operand:DI 0 "nonimmediate_operand" "=r,k,r,r,r,r ,r,*w,m,
> m,r,r, *w, r,*w,w")
> - (match_operand:DI 1 "aarch64_mov_operand" " r,r,k,N,n,Dv,m,
> m,rZ,*w,S,Ush,rZ,*w,*w,Dd"))]
> + (match_operand:DI 1 "aarch64_mov_operand" " r,r,k,N,n,Dv,m,
> m,rZ,*w,Usa,Ush,rZ,*w,*w,Dd"))]
> "(register_operand (operands[0], DImode)
> || aarch64_reg_or_zero (operands[1], DImode))"
> "@
> diff --git a/gcc/config/aarch64/constraints.md
> b/gcc/config/aarch64/constraints.md
> index b77e096..5852a42 100644
> --- a/gcc/config/aarch64/constraints.md
> +++ b/gcc/config/aarch64/constraints.md
> @@ -104,6 +104,14 @@
> (and (match_code "high")
> (match_test "aarch64_valid_symref (XEXP (op, 0), GET_MODE (XEXP (op,
> 0)))")))
>
> +(define_constraint "Usa"
> + "@internal
> + A constraint that matches an absolute symbolic address that can be
> + loaded by a single ADR."
> + (and (match_code "const,symbol_ref,label_ref")
> + (match_test "aarch64_symbolic_address_p (op)")
> + (match_test "aarch64_mov_operand_p (op, GET_MODE (op))")))
> +
> (define_constraint "Uss"
> "@internal
> A constraint that matches an immediate shift constant in SImode."
>
