AArch64: libm: Fix ARM64 fenv_t and refactor ARM64 libm implementation.

This patch fixes the ARM64 ABI for libm. fenv_t is now split in 32bit status
and 32bit control. This mirrors the AArch64 FPU control and status
registers (FPCR, FPSR).

The patch also refactors the libm implementation for ARM64 into a finer
grained control over the FPU registers.

Bionic-benchmarks has been expanded with 3 more benchmarks for floating
point operations. The new libm implementation for ARM64 performs better
over all the math benchmarks available.

Change-Id: I2a7f81d6b4e55c91f8a63a4c69614fc8b1bcf2db
Signed-off-by: Serban Constantinescu <serban.constantinescu@arm.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/benchmarks/math_benchmark.cpp b/benchmarks/math_benchmark.cpp
index 3602de4..a9748cd 100644
--- a/benchmarks/math_benchmark.cpp
+++ b/benchmarks/math_benchmark.cpp
@@ -16,6 +16,7 @@
 
 #include "benchmark.h"
 
+#include <fenv.h>
 #include <math.h>
 
 // Avoid optimization.
@@ -113,10 +114,49 @@ static void BM_math_isinf_ZERO(int iters) {
 }
 BENCHMARK(BM_math_isinf_ZERO);
 
+static void BM_math_sin_fast(int iters) {
+  StartBenchmarkTiming();
 
+  d = 1.0;
+  for (int i = 0; i < iters; ++i) {
+    d += sin(d);
+  }
+
+  StopBenchmarkTiming();
+}
+BENCHMARK(BM_math_sin_fast);
 
+static void BM_math_sin_feupdateenv(int iters) {
+  StartBenchmarkTiming();
 
+  d = 1.0;
+  for (int i = 0; i < iters; ++i) {
+    fenv_t __libc_save_rm;
+    feholdexcept(&__libc_save_rm);
+    fesetround(FE_TONEAREST);
+    d += sin(d);
+    feupdateenv(&__libc_save_rm);
+  }
 
+  StopBenchmarkTiming();
+}
+BENCHMARK(BM_math_sin_feupdateenv);
+
+static void BM_math_sin_fesetenv(int iters) {
+  StartBenchmarkTiming();
+
+  d = 1.0;
+  for (int i = 0; i < iters; ++i) {
+    fenv_t __libc_save_rm;
+    feholdexcept(&__libc_save_rm);
+    fesetround(FE_TONEAREST);
+    d += sin(d);
+    fesetenv(&__libc_save_rm);
+  }
+
+  StopBenchmarkTiming();
+}
+BENCHMARK(BM_math_sin_fesetenv);
 
 static void BM_math_fpclassify_NORMAL(int iters) {
   StartBenchmarkTiming();