powerpc: Cleanup fenv_private.h

Some of the masks are wrong, and the naming is confusing.

There are two basic cases we really care about:

1. Stacking a new rounding mode when running certain
   sections of code, and pausing exception handling.

2. Likewise, but discarding any exceptions which occur
   while running under the new rounding mode.

libc_feholdexcept_setround_ppc_ctx has been removed as it basically
does the same thing as libc_feholdsetround_ppc_ctx but also clearing
any sticky bits.  The restore behavior is what differentiates these
two cases as the SET_RESTORE_ROUND{,_NOEX} macros will either merge
or discard all exceptions occurring during scope of their usage.

Likewise, there are a number of routines to swap, replace,
or merge FP environments.  This change reduces much of
the common and sometimes wrong code.

Tested on ppc64le, with results before and after.

1 files changed, 42 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index 742aa8cdaf..d2b0b76578 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,45 @@
+2016-10-21  Paul E. Murphy  <murphyp@linux.vnet.ibm.com>
+
+	* sysdeps/powerpc/fpu/fenv_private.h:
+	(_FPU_MASK_ALL): Rename to...
+	(_FPU_ALL_TRAPS): New macro representing ISA VE OE UE ZE and
+	XE FPSCR bits.
+
+	(_FPU_MASK_RN): New macro to mask out ISA RN bits in FPSCR.
+
+	(_FPU_MASK_ROUNDING): Rename to...
+	(_FPU_MASK_NOT_RN_NI): New macro to mask out all but ISA RN and
+	NI bits.
+
+	(_FPU_MASK_EXCEPT_ROUND): Rename to...
+	(_FPU_MASK_TRAPS_RN): New macro to mask out exception enable
+	bits and rounding bits.
+
+	(__libc_feholdbits_ppc): New inline function to mask, set,
+	and pontentially clear FSPCR bits, and change MSR[FE] bits.
+	(libc_feholdexcept_ppc): Redefine using __libc_feholdbits_ppc.
+	(libc_feholdexcept_setround_ppc): Likewise.
+
+	(__libc_femergeenv_ppc): New function to dynamically mask both
+	old and new FP environments and merge.
+	(libc_fesetenv_ppc): Redefine in terms of __libc_femergeenv_ppc.
+	(libc_feresetround_ppc): Likewise.
+	(libc_feupdateenv_test_ppc): Likewise.
+	(libc_feupdateenv_ppc): Likewise.
+
+	(libc_feholdsetround_ppc_ctx): Fix usage to include masking
+	of ISA RN bits, and update macro names.
+	(libc_feholdexcept_setround_ppc_ctx): Remove as it is
+	effectively the same as the previously mentioned function.
+
+	(libc_feupdateenv_ppc_ctx): Replace libc_feupdatedenv_test_ppc
+	usage with fe_resetround_ppc.
+
+	(libc_feholdexcept_setround_ctx): Remove, this doesn't appear
+	to be used.
+	(libc_feholdexcept_setround_ctxf): Likewise.
+	(libc_feholdexcept_setround_ctxl): Likewise.
+
 2016-10-21  Florian Weimer  <fweimer@redhat.com>
 
 	[BZ #20715]