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[v5,00/23] tcg: Better handling of constants

Message ID 20201217145215.534637-1-richard.henderson@linaro.org
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Series tcg: Better handling of constants | expand

Message

Richard Henderson Dec. 17, 2020, 2:51 p.m. UTC 
Changes for v5:

Moved the clearing of the hash table from the end of compilation
to the beginning of compilation.  We skip the former when we long
jump out of the translator loop, e.g. touching a code page that
is unmapped.

Version 4 was back in May:
https://lists.gnu.org/archive/html/qemu-devel/2020-05/msg02152.html

Version 1 blurb:

This promotes constants to full-fledged temporaries, which are then
hashed so we have only a single copy across the TB.  If an opcode
requires forcing one into a register, then we will only do this
once -- at least until the register is killed, e.g. by a function call.

While this is probably an modest improvement for integer code, it is
significant for SVE vector code.  In particular, where a generator function
loads a constant for the operation, and then the generator function is
called N times for the N x 128-bit vector.  Previously we'd be loading
up the same constant N times and now we do so only once.

The existing tcg_const_{type}() functions are unchanged, allocating
a new temporary and initializing it.  The constant propagation pass
of the optimizer will generally remove the temporary when it turns
out not to be modified further.

This adds new tcg_constant_{type}() functions which produce a read-only
temporary containing the constant which need not be freed.  I have
updated the generic expanders to take advantage of this, but have not
touched the target front ends.

This also, in the end, allows the complete removal of the tcg opcodes
that create a constant: INDEX_op_movi_{i32,i64} and INDEX_op_dupi_vec.
Loading of constants into hard registers is completely controlled by
the register allocator.


r~


Richard Henderson (23):
  tcg: Use tcg_out_dupi_vec from temp_load
  tcg: Increase tcg_out_dupi_vec immediate to int64_t
  tcg: Consolidate 3 bits into enum TCGTempKind
  tcg: Add temp_readonly
  tcg: Expand TCGTemp.val to 64-bits
  tcg: Rename struct tcg_temp_info to TempOptInfo
  tcg: Expand TempOptInfo to 64-bits
  tcg: Introduce TYPE_CONST temporaries
  tcg/optimize: Improve find_better_copy
  tcg/optimize: Adjust TempOptInfo allocation
  tcg/optimize: Use tcg_constant_internal with constant folding
  tcg: Convert tcg_gen_dupi_vec to TCG_CONST
  tcg: Use tcg_constant_i32 with icount expander
  tcg: Use tcg_constant_{i32,i64} with tcg int expanders
  tcg: Use tcg_constant_{i32,i64} with tcg plugins
  tcg: Use tcg_constant_{i32,i64,vec} with gvec expanders
  tcg/tci: Add special tci_movi_{i32,i64} opcodes
  tcg: Remove movi and dupi opcodes
  tcg: Add tcg_reg_alloc_dup2
  tcg/i386: Use tcg_constant_vec with tcg vec expanders
  tcg: Remove tcg_gen_dup{8,16,32,64}i_vec
  tcg/ppc: Use tcg_constant_vec with tcg vec expanders
  tcg/aarch64: Use tcg_constant_vec with tcg vec expanders

 include/exec/gen-icount.h    |  25 +-
 include/tcg/tcg-op.h         |  17 +-
 include/tcg/tcg-opc.h        |  11 +-
 include/tcg/tcg.h            |  50 +++-
 accel/tcg/plugin-gen.c       |  49 ++--
 tcg/optimize.c               | 249 +++++++++---------
 tcg/tcg-op-gvec.c            | 125 ++++-----
 tcg/tcg-op-vec.c             |  52 +---
 tcg/tcg-op.c                 | 227 ++++++++--------
 tcg/tcg.c                    | 488 +++++++++++++++++++++++++++--------
 tcg/tci.c                    |   4 +-
 tcg/aarch64/tcg-target.c.inc |  32 +--
 tcg/arm/tcg-target.c.inc     |   1 -
 tcg/i386/tcg-target.c.inc    | 112 ++++----
 tcg/mips/tcg-target.c.inc    |   2 -
 tcg/ppc/tcg-target.c.inc     |  90 ++++---
 tcg/riscv/tcg-target.c.inc   |   2 -
 tcg/s390/tcg-target.c.inc    |   2 -
 tcg/sparc/tcg-target.c.inc   |   2 -
 tcg/tci/tcg-target.c.inc     |   6 +-
 20 files changed, 882 insertions(+), 664 deletions(-)

-- 
2.25.1