reload and constrain_operands had some old code to look through unary
operators. E.g. an operand could be (sign_extend (reg X)), and the
constraints would match the reg rather than the sign_extend.
This was previously used by the MIPS port. But relying on it was a
recurring source of problems, so Eric and I removed it in the MIPS
rewrite from ~20 years back. I don't know of any other port that used it.
Also, the constraints processing in LRA and IRA do not have direct
support for these embedded operators, so I think it was only ever a
reload-specific feature (and probably only a global/local+reload-specific
feature, rather than IRA+reload).
Keeping the checks caused problems for special memory constraints,
leading to:
/* A unary operator may be accepted by the predicate, but it
is irrelevant for matching constraints. */
/* For special_memory_operand, there could be a memory operand inside,
and it would cause a mismatch for constraint_satisfied_p. */
if (UNARY_P (op) && op == extract_mem_from_operand (op))
op = XEXP (op, 0);
But inline asms are another source of problems. Asms don't have
predicates, and so we can't use recog to decide whether a given change
to an asm gives a valid match. We instead rely on constrain_operands as
something of a recog stand-in. For an example like:
void
foo (int *ptr)
{
asm volatile ("%0" :: "r" (-*ptr));
}
any attempt to propagate the negation into the asm would be allowed,
because it's the negated register that would be checked against the
"r" constraint. This would later lead to:
error: invalid 'asm': invalid operand
The same thing happened in gcc.target/aarch64/vneg_s.c with the
upcoming late-combine pass.
Rather than add more workarounds, it seemed better just to delete
this code.
Tested on aarch64-linux-gnu & x86_64-linux-gnu. OK to install?
Richard
gcc/
* recog.cc (constrain_operands): Remove UNARY_P handling.
* reload.cc (find_reloads): Likewise.
---
gcc/recog.cc | 15 ---------------
gcc/reload.cc | 6 ------
2 files changed, 21 deletions(-)
diff --git a/gcc/recog.cc b/gcc/recog.cc
index 92f151248a6..e12b4c9500e 100644
--- a/gcc/recog.cc
+++ b/gcc/recog.cc
@@ -3080,13 +3080,6 @@ constrain_operands (int strict, alternative_mask
alternatives)
earlyclobber[opno] = 0;
- /* A unary operator may be accepted by the predicate, but it
- is irrelevant for matching constraints. */
- /* For special_memory_operand, there could be a memory operand inside,
- and it would cause a mismatch for constraint_satisfied_p. */
- if (UNARY_P (op) && op == extract_mem_from_operand (op))
- op = XEXP (op, 0);
-
if (GET_CODE (op) == SUBREG)
{
if (REG_P (SUBREG_REG (op))
@@ -3152,14 +3145,6 @@ constrain_operands (int strict, alternative_mask
alternatives)
{
rtx op1 = recog_data.operand[match];
rtx op2 = recog_data.operand[opno];
-
- /* A unary operator may be accepted by the predicate,
- but it is irrelevant for matching constraints. */
- if (UNARY_P (op1))
- op1 = XEXP (op1, 0);
- if (UNARY_P (op2))
- op2 = XEXP (op2, 0);
-
val = operands_match_p (op1, op2);
}
diff --git a/gcc/reload.cc b/gcc/reload.cc
index 2e57ebb3cac..07256b6cf2f 100644
--- a/gcc/reload.cc
+++ b/gcc/reload.cc
@@ -3077,12 +3077,6 @@ find_reloads (rtx_insn *insn, int replace, int
ind_levels, int live_known,
enum constraint_num cn;
enum reg_class cl;
- /* If the predicate accepts a unary operator, it means that
- we need to reload the operand, but do not do this for
- match_operator and friends. */
- if (UNARY_P (operand) && *p != 0)
- operand = XEXP (operand, 0);
-
/* If the operand is a SUBREG, extract
the REG or MEM (or maybe even a constant) within.
(Constants can occur as a result of reg_equiv_constant.) */
--
2.25.1
