Memory operands store a base alignment that does not factor in
the effect of the offset on the alignment.
Previously the printing code only printed the base alignment if
it was different than the size. If there is an offset, the reader
would need to figure out the effective alignment themselves. This
has confused me before and someone else was recently confused on
IRC.
This patch prints the possibly offset adjusted alignment if it is
different than the size. And prints the base alignment if it is
different than the alignment. The MIR parser has been updated to
read basealign in addition to align.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D94344
This rewrites big parts of the fast register allocator. The basic
strategy of doing block-local allocation hasn't changed but I tweaked
several details:
Track register state on register units instead of physical
registers. This simplifies and speeds up handling of register aliases.
Process basic blocks in reverse order: Definitions are known to end
register livetimes when walking backwards (contrary when walking
forward then uses may or may not be a kill so we need heuristics).
Check register mask operands (calls) instead of conservatively
assuming everything is clobbered. Enhance heuristics to detect
killing uses: In case of a small number of defs/uses check if they are
all in the same basic block and if so the last one is a killing use.
Enhance heuristic for copy-coalescing through hinting: We check the
first k defs of a register for COPYs rather than relying on there just
being a single definition. When testing this on the full llvm
test-suite including SPEC externals I measured:
average 5.1% reduction in code size for X86, 4.9% reduction in code on
aarch64. (ranging between 0% and 20% depending on the test) 0.5%
faster compiletime (some analysis suggests the pass is slightly slower
than before, but we more than make up for it because later passes are
faster with the reduced instruction count)
Also adds a few testcases that were broken without this patch, in
particular bug 47278.
Patch mostly by Matthias Braun
