Add compat compiler to enable VDSO

(with the patch decon0 takes a lot of CPU so needs investigation)

This patch adds a compat compiler that enables
the VDSO generation for 32bit

VDSO improves the time functions by up to 30x

Pre patch performance:

130|r11:/data/local # ./bionic-benchmarks --benchmark_filter=BM_time_clock*
2021-05-04 18:34:37
Running ./bionic-benchmarks
Run on (2 X 1144 MHz CPU s)
***WARNING*** CPU scaling is enabled, the benchmark real time measurements may be noisy and will incur extra overhead.
---------------------------------------------------------------------------------
Benchmark                                       Time             CPU   Iterations
---------------------------------------------------------------------------------
BM_time_clock_getres                         1434 ns         1433 ns       488235
BM_time_clock_getres_BOOTTIME                1435 ns         1434 ns       487981
BM_time_clock_getres_MONOTONIC_COARSE        1459 ns         1458 ns       480207
BM_time_clock_getres_MONOTONIC_RAW           1448 ns         1441 ns       488421
BM_time_clock_getres_REALTIME                1436 ns         1434 ns       488180
BM_time_clock_getres_REALTIME_COARSE         1458 ns         1458 ns       480123
BM_time_clock_getres_syscall                 1413 ns         1413 ns       495407
BM_time_clock_gettime                        1736 ns         1736 ns       403663
BM_time_clock_gettime_BOOTTIME               1746 ns         1745 ns       401205
BM_time_clock_gettime_MONOTONIC_COARSE       1485 ns         1484 ns       471822
BM_time_clock_gettime_MONOTONIC_RAW          1715 ns         1714 ns       408407
BM_time_clock_gettime_REALTIME               1715 ns         1714 ns       408397
BM_time_clock_gettime_REALTIME_COARSE        1459 ns         1459 ns       479789
BM_time_clock_gettime_syscall                1711 ns         1711 ns       407826

post patch:

---------------------------------------------------------------------------------
Benchmark                                       Time             CPU   Iterations
---------------------------------------------------------------------------------
BM_time_clock_getres                         41.4 ns         39.9 ns     17566596
BM_time_clock_getres_BOOTTIME                39.9 ns         39.8 ns     17665970
BM_time_clock_getres_MONOTONIC_COARSE        40.6 ns         40.6 ns     17216056
BM_time_clock_getres_MONOTONIC_RAW           40.3 ns         39.8 ns     17607225
BM_time_clock_getres_REALTIME                39.7 ns         39.6 ns     17548755
BM_time_clock_getres_REALTIME_COARSE         40.5 ns         40.5 ns     17288572
BM_time_clock_getres_syscall                 1417 ns         1415 ns       495227
BM_time_clock_gettime                        1765 ns         1763 ns       395992
BM_time_clock_gettime_BOOTTIME               1775 ns         1774 ns       393764
BM_time_clock_gettime_MONOTONIC_COARSE       75.7 ns         75.6 ns      9251004
BM_time_clock_gettime_MONOTONIC_RAW          1802 ns         1801 ns       388419
BM_time_clock_gettime_REALTIME               1744 ns         1744 ns       401373
BM_time_clock_gettime_REALTIME_COARSE        75.6 ns         75.6 ns      9254838
BM_time_clock_gettime_syscall                1705 ns         1705 ns       409374

Still need to investigate the gettime_BOOTTIME/REALTIME/MONOTONIC_RAW to
see if it's expected to not gain performance

Bug: 187240443
Test: local on device
Change-Id: I11b6b1be0ccc02a5d3b34fd0904b8367858cf43f

1 files changed, 2 insertions, 0 deletions

diff --git a/build.config b/build.config
index 6ece051..35a9d77 100644
--- a/build.config
+++ b/build.config
@@ -30,6 +30,8 @@ KMI_GENERATION=0
 LLVM=1
 DEPMOD=depmod
 
+CROSS_COMPILE_COMPAT=arm-linux-androidkernel-
+
 ARCH=arm64
 BRANCH=android-exynos-r11-4.19
 CROSS_COMPILE=aarch64-linux-android-