constraint: fix relaxed memory and repeated constraint handling
Commit Message
The function `constrain_operands' lacked the logic to consider relaxed
memory constraints when "traditional" memory constraints were not
satisfied, creating potential issues as observed during the reload
compilation pass.
In addition, it was observed that while `constrain_operands' chooses
to disregard constraints when more than one alternative is provided,
e.g. "m,r" using CONSTRAINT__UNKNOWN, it has no checks in place to
determine whether the multiple constraints in a given string are in
fact repetitions of the same constraint and should thus in fact be
treated as a single constraint, as ought to be the case for something
like "m,m".
Both of these issues are dealt with here, thus ensuring that we get
appropriate pattern matching.
Tested on aarch64-linux-gnu & x86_64-linux-gnu. OK to install?
Victor
gcc/
* lra-constraints.cc (constraint_unique): New.
(process_address_1): Apply constraint_unique test.
* recog.cc (constrain_operands): Allow relaxed memory
constaints.
---
gcc/lra-constraints.cc | 40 +++++++++++++++++++++++++++++++++++++---
gcc/recog.cc | 3 ++-
2 files changed, 39 insertions(+), 4 deletions(-)
Comments
"Victor L. Do Nascimento" <victor.donascimento@arm.com> writes:
> The function `constrain_operands' lacked the logic to consider relaxed
> memory constraints when "traditional" memory constraints were not
> satisfied, creating potential issues as observed during the reload
> compilation pass.
>
> In addition, it was observed that while `constrain_operands' chooses
> to disregard constraints when more than one alternative is provided,
> e.g. "m,r" using CONSTRAINT__UNKNOWN, it has no checks in place to
> determine whether the multiple constraints in a given string are in
> fact repetitions of the same constraint and should thus in fact be
> treated as a single constraint, as ought to be the case for something
> like "m,m".
>
> Both of these issues are dealt with here, thus ensuring that we get
> appropriate pattern matching.
>
> Tested on aarch64-linux-gnu & x86_64-linux-gnu. OK to install?
>
> Victor
>
> gcc/
> * lra-constraints.cc (constraint_unique): New.
> (process_address_1): Apply constraint_unique test.
> * recog.cc (constrain_operands): Allow relaxed memory
> constaints.
> ---
> gcc/lra-constraints.cc | 40 +++++++++++++++++++++++++++++++++++++---
> gcc/recog.cc | 3 ++-
> 2 files changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
> index dd4f68bbfc0..6a13e64d7e1 100644
> --- a/gcc/lra-constraints.cc
> +++ b/gcc/lra-constraints.cc
> @@ -3448,6 +3448,42 @@ skip_constraint_modifiers (const char *str)
> }
> }
>
> +/* Takes a string of 0 or more comma-separated constraints and the
> + constraint_num correspondig to the first constraint. When more
corresponding
> + than one constraint present, evaluate whether they all correspond
is present
> + to a single, repeated constraint (e.g. "r,r") or whether we have
> + more than one distinct constraints (e.g. "r,m"). */
> +static bool
> +constraint_unique (const char *cstr)
> +{
> + enum constraint_num ca, cb;
> + ca = CONSTRAINT__UNKNOWN;
> + for (;;)
> + {
> + cstr = skip_constraint_modifiers (cstr);
> + if (*cstr == '\0' || *cstr == ',')
> + cb = CONSTRAINT_X;
> + else
> + {
> + cb = lookup_constraint (cstr);
> + if (cb == CONSTRAINT__UNKNOWN)
> + return false;
> + cstr += CONSTRAINT_LEN (cstr[0], cstr);
> + }
> + /* Treat the special case of an uninitialized ca. */
Maybe: /* Handle the first iteration of the loop. */
> + if (ca == CONSTRAINT__UNKNOWN)
> + ca = cb;
> + /* Treat the general case of comparing ca with subsequent
> + constraints. */
s/Treat/Handle/
OK with those changes, thanks.
Richard
> + else if (ca != cb)
> + return false;
> + if (*cstr == '\0')
> + return true;
> + if (*cstr == ',')
> + cstr += 1;
> + }
> +}
> +
> /* Major function to make reloads for an address in operand NOP or
> check its correctness (If CHECK_ONLY_P is true). The supported
> cases are:
> @@ -3507,9 +3543,7 @@ process_address_1 (int nop, bool check_only_p,
> operand has one address constraint, probably all others constraints are
> address ones. */
> if (constraint[0] != '\0' && get_constraint_type (cn) != CT_ADDRESS
> - && *skip_constraint_modifiers (constraint
> - + CONSTRAINT_LEN (constraint[0],
> - constraint)) != '\0')
> + && !constraint_unique (constraint))
> cn = CONSTRAINT__UNKNOWN;
> if (insn_extra_address_constraint (cn)
> /* When we find an asm operand with an address constraint that
> diff --git a/gcc/recog.cc b/gcc/recog.cc
> index 200cf4214f1..3ddeab59d92 100644
> --- a/gcc/recog.cc
> +++ b/gcc/recog.cc
> @@ -3234,7 +3234,8 @@ constrain_operands (int strict, alternative_mask alternatives)
> else if (constraint_satisfied_p (op, cn))
> win = 1;
>
> - else if (insn_extra_memory_constraint (cn)
> + else if ((insn_extra_memory_constraint (cn)
> + || insn_extra_relaxed_memory_constraint (cn))
> /* Every memory operand can be reloaded to fit. */
> && ((strict < 0 && MEM_P (op))
> /* Before reload, accept what reload can turn
@@ -3448,6 +3448,42 @@ skip_constraint_modifiers (const char *str)
}
}
+/* Takes a string of 0 or more comma-separated constraints and the
+ constraint_num correspondig to the first constraint. When more
+ than one constraint present, evaluate whether they all correspond
+ to a single, repeated constraint (e.g. "r,r") or whether we have
+ more than one distinct constraints (e.g. "r,m"). */
+static bool
+constraint_unique (const char *cstr)
+{
+ enum constraint_num ca, cb;
+ ca = CONSTRAINT__UNKNOWN;
+ for (;;)
+ {
+ cstr = skip_constraint_modifiers (cstr);
+ if (*cstr == '\0' || *cstr == ',')
+ cb = CONSTRAINT_X;
+ else
+ {
+ cb = lookup_constraint (cstr);
+ if (cb == CONSTRAINT__UNKNOWN)
+ return false;
+ cstr += CONSTRAINT_LEN (cstr[0], cstr);
+ }
+ /* Treat the special case of an uninitialized ca. */
+ if (ca == CONSTRAINT__UNKNOWN)
+ ca = cb;
+ /* Treat the general case of comparing ca with subsequent
+ constraints. */
+ else if (ca != cb)
+ return false;
+ if (*cstr == '\0')
+ return true;
+ if (*cstr == ',')
+ cstr += 1;
+ }
+}
+
/* Major function to make reloads for an address in operand NOP or
check its correctness (If CHECK_ONLY_P is true). The supported
cases are:
@@ -3507,9 +3543,7 @@ process_address_1 (int nop, bool check_only_p,
operand has one address constraint, probably all others constraints are
address ones. */
if (constraint[0] != '\0' && get_constraint_type (cn) != CT_ADDRESS
- && *skip_constraint_modifiers (constraint
- + CONSTRAINT_LEN (constraint[0],
- constraint)) != '\0')
+ && !constraint_unique (constraint))
cn = CONSTRAINT__UNKNOWN;
if (insn_extra_address_constraint (cn)
/* When we find an asm operand with an address constraint that
@@ -3234,7 +3234,8 @@ constrain_operands (int strict, alternative_mask alternatives)
else if (constraint_satisfied_p (op, cn))
win = 1;
- else if (insn_extra_memory_constraint (cn)
+ else if ((insn_extra_memory_constraint (cn)
+ || insn_extra_relaxed_memory_constraint (cn))
/* Every memory operand can be reloaded to fit. */
&& ((strict < 0 && MEM_P (op))
/* Before reload, accept what reload can turn