270b1bc...
by
Alexandre Oliva <email address hidden>
[PR67355] drop dummy zero from reverse VTA ops, fix infinite recursion
VTA's cselib expression hashing compares expressions with the same
hash before adding them to the hash table. When there is a collision
involving a self-referencing expression, we could get infinite
recursion, in spite of the cycle breakers already in place. The
problem is currently latent in the trunk, because by chance we don't
get a collision.
Such value cycles are often introduced by reverse_op; most often,
they're indirect, and then value canonicalization takes care of the
cycle, but if the reverse operation simplifies to the original value,
we used to issue a (plus V (const_int 0)), because at some point
adding a plain value V to a location list as a reverse_op equivalence
caused other problems.
This dummy zero, in turn, caused the value canonicalizer to not fully
realize the equivalence, leading to more complex graphs and,
occasionally, to infinite recursion when comparing such
value-plus-zero expressions recursively.
Simply using V solves the infinite recursion from the PR testcase,
since the extra equivalence and the preexisting value canonicalization
together prevent recursion while the unrecognized equivalence
wouldn't, but it exposed another infinite recursion in
memrefs_conflict_p: get_addr had a cycle breaker in place, to skip RTL
referencing values introduced after the one we're examining, but it
wouldn't break the cycle if the value itself appeared in the
expression being examined.
After removing the dummy zero above, this kind of cycle in the
equivalence graph is no longer introduced by VTA itself, but dummy
zeros are also present in generated code, such as in the 32-bit x86's
pro_epilogue_adjust_stack_si_add epilogue insn generated as part of
the builtin longjmp in _Unwind_RaiseException building libgcc's
unwind-dw2.o. So, break the recursion cycle for them too.
for gcc/ChangeLog
PR debug/67355
* var-tracking.c (reverse_op): Don't add dummy zero to reverse
ops that simplify back to the original value.
* alias.c (refs_newer_value_p): Cut off recursion for
expressions containing the original value.
4b8026f...
by
aoliva <aoliva@138bc75d-0d04-0410-961f-82ee72b054a4>
[PR67753] adjust for padding when bypassing memory in assign_parm_setup_block
Storing a register in memory as a full word and then accessing the
same memory address under a smaller-than-word mode amounts to
right-shifting of the register word on big endian machines. So, if
BLOCK_REG_PADDING chooses upward padding for BYTES_BIG_ENDIAN, and
we're copying from the entry_parm REG directly to a pseudo, bypassing
any stack slot, perform the shifting explicitly.
This fixes the miscompile of function_return_val_10 in
gcc.target/aarch64/aapcs64/func-ret-4.c for target aarch64_be-elf
introduced in the first patch for 67753.
for gcc/ChangeLog
PR rtl-optimization/67753
PR rtl-optimization/64164
* function.c (assign_parm_setup_block): Right-shift
upward-padded big-endian args when bypassing the stack slot.
db5ba70...
by
macro <macro@138bc75d-0d04-0410-961f-82ee72b054a4>
MIPS/GCC/doc: Reorder `-mcompact-branches='
Move the `-mcompact-branches=' option out of the middle of a block of
floating-point options. The option is not related to FP in any way.
Place it immediately below other branch instruction selection options.
