gcse: Fix handling of partial clobbers [PR97497]

This patch fixes an internal disagreement in gcse about how to
handle partial clobbers.  Like many passes, gcse doesn't track
the modes of live values, so if a call clobbers only part of
a register, the pass has to make conservative assumptions.
As the comment in the patch says, this means:

(1) ignoring partial clobbers when computing liveness and reaching
    definitions

(2) treating partial clobbers as full clobbers when computing
    availability

DF is mostly concerned with (1), so ignores partial clobbers.

compute_hash_table_work did (2) when calculating kill sets,
but compute_transp didn't do (2) when computing transparency.
This led to a nonsensical situation of a register being in both
the transparency and kill sets.

gcc/
	PR rtl-optimization/97497
	* function-abi.h (predefined_function_abi::only_partial_reg_clobbers)
	(function_abi::only_partial_reg_clobbers): New member functions.
	* gcse-common.cc: Include regs.h and function-abi.h.
	(compute_transp): Check for partially call-clobbered registers
	and treat them as not being transparent in blocks with calls.

0 files changed, 0 insertions, 0 deletions