[PATCH 0/7] exec: Improve code for TARGET_PAGE_BITS_VARY

[Richard Henderson]

There's currently a fair amount of overhead in the way we currently
treat TARGET_PAGE_{BITS,SIZE,MASK} with TARGET_PAGE_BITS_VARY.

We have assertions that TARGET_PAGE_BITS has been finalized.  Which
is fine, but the variable that controls the assertion may be assumed
to be modified by any function call, which means that we have lots
of duplicate assertions.

This re-arranges things using a const symbol, which allows the compiler
to assume that the variable is not modified across calls.  In order to
allow initialization of the variable during startup, use an alias that
is non-const and controls the allocation into a read-write section.

Remove the assertion for release builds.

Precompute TARGET_PAGE_MASK.  This removes a runtime shift and allows
the variable to be used as a direct memory operand on x86.

Size reductions vs master for qemu-system-aarch64 for various hosts:

PPC64LE:
  debug-tcg:  -32264
  release:    -44360
AARCH64:
  debug-tcg:  -33304
  relase:     -77080
X86_64:
  debug-tcg:   -6685
  relase:     -15597


r~


Richard Henderson (7):
  exec: Use TARGET_PAGE_BITS_MIN for TLB flags
  exec: Split out variable page size support to exec-vary.c
  exec: Use const alias for TARGET_PAGE_BITS_VARY
  exec: Restrict TARGET_PAGE_BITS_VARY assert to CONFIG_DEBUG_TCG
  exec: Promote TARGET_PAGE_MASK to target_long
  exec: Tidy TARGET_PAGE_ALIGN
  exec: Cache TARGET_PAGE_MASK for TARGET_PAGE_BITS_VARY

 Makefile.target        |  2 +-
 include/exec/cpu-all.h | 41 +++++++++++++-------
 include/qemu-common.h  |  6 +++
 exec-vary.c            | 88 ++++++++++++++++++++++++++++++++++++++++++
 exec.c                 | 34 ----------------
 5 files changed, 123 insertions(+), 48 deletions(-)
 create mode 100644 exec-vary.c

-- 
2.17.1