diff options
author | Miod Vallat <miod@cvs.openbsd.org> | 2012-12-01 22:54:03 +0000 |
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committer | Miod Vallat <miod@cvs.openbsd.org> | 2012-12-01 22:54:03 +0000 |
commit | b02dfe0ab7aae6700f0c15419373891118eab134 (patch) | |
tree | 535b6d29222cbe7e3bb3fe3d6f9637f31e93face /bin/kill/kill.1 | |
parent | a06516e47e752c824b8c4c1a049b5e408d3ba696 (diff) |
reload_cse_noop_set_p(): invoking rtx_equal_for_cselib_p() is not enough; if
it reports the dest and source parts of the set insn are identical, we need
to check whether they are volatile memory references, and return 0 (not a
noop) in that case.
This allows `*volatile_ptr = *volatile_ptr;' constructs to no longer be
incorrectly optimized away on platforms which can perform memory to memory
transfers in a single instruction (i.e. m68k and vax).
Found the hard way on vax, where some systems need to frob the interrupt
stack early, before being able to handle faults, and a gcc3-built kernel
would have this operation optimized away, leading to a quick system reset.
Diffstat (limited to 'bin/kill/kill.1')
0 files changed, 0 insertions, 0 deletions