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| author | Wilco <wdijkstr@arm.com> | 2014-06-24 13:53:04 +0000 |
|---|---|---|
| committer | Wilco <wdijkstr@arm.com> | 2014-06-24 13:53:04 +0000 |
| commit | db59bad394ef61bf6d6ef7916012f2a09d0b3d11 (patch) | |
| tree | 9605e6411433339e020a53841702db0171efaf81 | |
| parent | 001f7b773c637560ecfa686452a5e68d60d07db3 (diff) | |
| download | glibc-db59bad394ef61bf6d6ef7916012f2a09d0b3d11.tar.gz glibc-db59bad394ef61bf6d6ef7916012f2a09d0b3d11.tar.xz glibc-db59bad394ef61bf6d6ef7916012f2a09d0b3d11.zip | |
Rewrite feupdateenv
This patch rewrites feupdateenv to improve performance by avoiding unnecessary FPSCR reads/writes. It fixes bug 16918 by passing the correct return value. 2014-06-24 Wilco <wdijkstr@arm.com> [BZ #16918] * sysdeps/arm/feupdateenv.c (feupdateenv): Rewrite to reduce FPSCR accesses and fix return value.
| -rw-r--r-- | ChangeLog | 6 | ||||
| -rw-r--r-- | sysdeps/arm/feupdateenv.c | 44 |
2 files changed, 44 insertions, 6 deletions
diff --git a/ChangeLog b/ChangeLog index 0b0f61affa..3330b0b98b 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,11 @@ 2014-06-24 Wilco <wdijkstr@arm.com> + [BZ #16918] + * sysdeps/arm/feupdateenv.c (feupdateenv): + Rewrite to reduce FPSCR accesses and fix return value. + +2014-06-24 Wilco <wdijkstr@arm.com> + * sysdeps/arm/fclrexcpt.c (feclearexcept): Optimize to avoid unnecessary FPSCR writes. * sysdeps/arm/fedisblxcpt.c (fedisableexcept): Likewise. diff --git a/sysdeps/arm/feupdateenv.c b/sysdeps/arm/feupdateenv.c index 55a15025c6..d8116789d0 100644 --- a/sysdeps/arm/feupdateenv.c +++ b/sysdeps/arm/feupdateenv.c @@ -18,26 +18,58 @@ <http://www.gnu.org/licenses/>. */ #include <fenv.h> -#include <fpu_control.h> #include <arm-features.h> int feupdateenv (const fenv_t *envp) { - fpu_control_t fpscr; + fpu_control_t fpscr, new_fpscr, updated_fpscr; + int excepts; /* Fail if a VFP unit isn't present. */ if (!ARM_HAVE_VFP) return 1; _FPU_GETCW (fpscr); + excepts = fpscr & FE_ALL_EXCEPT; - /* Install new environment. */ - fesetenv (envp); + if ((envp != FE_DFL_ENV) && (envp != FE_NOMASK_ENV)) + { + /* Merge current exception flags with the saved fenv. */ + new_fpscr = envp->__cw | excepts; + + /* Write new FPSCR if different (ignoring NZCV flags). */ + if (((fpscr ^ new_fpscr) & ~_FPU_MASK_NZCV) != 0) + _FPU_SETCW (new_fpscr); + + /* Raise the exceptions if enabled in the new FP state. */ + if (excepts & (new_fpscr >> FE_EXCEPT_SHIFT)) + return feraiseexcept (excepts); + + return 0; + } + + /* Preserve the reserved FPSCR flags. */ + new_fpscr = fpscr & (_FPU_RESERVED | FE_ALL_EXCEPT); + new_fpscr |= (envp == FE_DFL_ENV) ? _FPU_DEFAULT : _FPU_IEEE; + + if (((new_fpscr ^ fpscr) & ~_FPU_MASK_NZCV) != 0) + { + _FPU_SETCW (new_fpscr); + + /* Not all VFP architectures support trapping exceptions, so + test whether the relevant bits were set and fail if not. */ + _FPU_GETCW (updated_fpscr); + + if (new_fpscr & ~updated_fpscr) + return 1; + } + + /* Raise the exceptions if enabled in the new FP state. */ + if (excepts & (new_fpscr >> FE_EXCEPT_SHIFT)) + return feraiseexcept (excepts); - /* Raise the saved exceptions. */ - feraiseexcept (fpscr & FE_ALL_EXCEPT); return 0; } libm_hidden_def (feupdateenv) |