On 20/09/19 01:29, Richard Henderson wrote:
> 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
>
Reviewed-by: Paolo Bonzini <[email protected]>
