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 <pbonz...@redhat.com>