Eric Botcazou <ebotca...@adacore.com> writes:
> > The condition would look like this, What do you think?
> >
> > if (!(GET_MODE_PRECISION (mode) != GET_MODE_PRECISION (innermode)
> > && GET_MODE_SIZE (mode) <= UNITS_PER_WORD
> > && GET_MODE_SIZE (innermode) <= UNITS_PER_WORD
> > && WORD_REGISTER_OPERATIONS)
> > && (!(MEM_ALIGN (subst) < GET_MODE_ALIGNMENT (mode)
> > && SLOW_UNALIGNED_ACCESS (mode, MEM_ALIGN (subst)))
> >
> > || (MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (innermode)
> >
> > && SLOW_UNALIGNED_ACCESS (innermode, MEM_ALIGN
> > (reg))))) return true;
>
> No regressions on SPARC.
I have committed this change now. The final patch is below. I will respond
promptly if there is some further unexpected fallout from this. I built the
arm-none-eabi target successfully as an additional check and bootstrapped
mips64el-linux-gnu as well. I'll have to rely on the various auto-builders
people have to cover all the testsuite variations as I'm not set up to cover
them all myself.
Thanks,
Matthew
gcc/
PR target/78660
* lra-constraints.c (simplify_operand_subreg): Handle
WORD_REGISTER_OPERATIONS targets.
diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index 35539a9..224a956 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -1541,11 +1541,22 @@ simplify_operand_subreg (int nop, machine_mode reg_mode)
subregs as we don't substitute such equiv memory (see processing
equivalences in function lra_constraints) and because for spilled
pseudos we allocate stack memory enough for the biggest
- corresponding paradoxical subreg. */
- if (!(MEM_ALIGN (subst) < GET_MODE_ALIGNMENT (mode)
- && SLOW_UNALIGNED_ACCESS (mode, MEM_ALIGN (subst)))
- || (MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (innermode)
- && SLOW_UNALIGNED_ACCESS (innermode, MEM_ALIGN (reg))))
+ corresponding paradoxical subreg.
+
+ However, do not blindly simplify a (subreg (mem ...)) for
+ WORD_REGISTER_OPERATIONS targets as this may lead to loading junk
+ data into a register when the inner is narrower than outer or
+ missing important data from memory when the inner is wider than
+ outer. This rule only applies to modes that are no wider than
+ a word. */
+ if (!(GET_MODE_PRECISION (mode) != GET_MODE_PRECISION (innermode)
+ && GET_MODE_SIZE (mode) <= UNITS_PER_WORD
+ && GET_MODE_SIZE (innermode) <= UNITS_PER_WORD
+ && WORD_REGISTER_OPERATIONS)
+ && (!(MEM_ALIGN (subst) < GET_MODE_ALIGNMENT (mode)
+ && SLOW_UNALIGNED_ACCESS (mode, MEM_ALIGN (subst)))
+ || (MEM_ALIGN (reg) < GET_MODE_ALIGNMENT (innermode)
+ && SLOW_UNALIGNED_ACCESS (innermode, MEM_ALIGN (reg)))))
return true;
*curr_id->operand_loc[nop] = operand;
--
2.2.1
