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.

2 files changed, 95 insertions, 103 deletions

diff --git a/ChangeLog b/ChangeLog
index 742aa8c..d2b0b76 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]
diff --git a/sysdeps/powerpc/fpu/fenv_private.h b/sysdeps/powerpc/fpu/fenv_private.h
index 02ac980..ecc05bc 100644
--- a/sysdeps/powerpc/fpu/fenv_private.h
+++ b/sysdeps/powerpc/fpu/fenv_private.h
@@ -23,56 +23,58 @@
 #include <fenv_libc.h>
 #include <fpu_control.h>
 
-#define _FPU_MASK_ALL (_FPU_MASK_ZM | _FPU_MASK_OM | _FPU_MASK_UM \
+/* Mask for the exception enable bits.  */
+#define _FPU_ALL_TRAPS (_FPU_MASK_ZM | _FPU_MASK_OM | _FPU_MASK_UM \
                       | _FPU_MASK_XM | _FPU_MASK_IM)
 
+/* Mask the rounding mode bits.  */
+#define _FPU_MASK_RN (~0x3)
+
 /* Mask everything but the rounding moded and non-IEEE arithmetic flags.  */
-#define _FPU_MASK_ROUNDING 0xffffffff00000007LL
+#define _FPU_MASK_NOT_RN_NI 0xffffffff00000007LL
 
 /* Mask restore rounding mode and exception enabled.  */
-#define _FPU_MASK_EXCEPT_ROUND 0xffffffff1fffff00LL
+#define _FPU_MASK_TRAPS_RN 0xffffffff1fffff00LL
 
 /* Mask exception enable but fraction rounded/inexact and FP result/CC
    bits.  */
-#define _FPU_MASK_FRAC_INEX_RET_CC 0x1ff80fff
+#define _FPU_MASK_FRAC_INEX_RET_CC 0xffffffff1ff80fff
 
 static __always_inline void
-libc_feholdexcept_ppc (fenv_t *envp)
+__libc_feholdbits_ppc (fenv_t *envp, unsigned long long mask,
+	unsigned long long bits)
 {
   fenv_union_t old, new;
 
   old.fenv = *envp = fegetenv_register ();
 
-  new.l = old.l & _FPU_MASK_ROUNDING;
+  new.l = (old.l & mask) | bits;
 
   /* If the old env had any enabled exceptions, then mask SIGFPE in the
      MSR FE0/FE1 bits.  This may allow the FPU to run faster because it
      always takes the default action and can not generate SIGFPE.  */
-  if ((old.l & _FPU_MASK_ALL) != 0)
+  if ((old.l & _FPU_ALL_TRAPS) != 0)
     (void) __fe_mask_env ();
 
   fesetenv_register (new.fenv);
 }
 
 static __always_inline void
-libc_fesetround_ppc (int r)
+libc_feholdexcept_ppc (fenv_t *envp)
 {
-  __fesetround_inline (r);
+  __libc_feholdbits_ppc (envp, _FPU_MASK_NOT_RN_NI, 0LL);
 }
 
 static __always_inline void
 libc_feholdexcept_setround_ppc (fenv_t *envp, int r)
 {
-  fenv_union_t old, new;
-
-  old.fenv = *envp = fegetenv_register ();
-
-  new.l = (old.l & _FPU_MASK_ROUNDING) | r;
-
-  if ((old.l & _FPU_MASK_ALL) != 0)
-    (void) __fe_mask_env ();
+  __libc_feholdbits_ppc (envp, _FPU_MASK_NOT_RN_NI & _FPU_MASK_RN, r);
+}
 
-  fesetenv_register (new.fenv);
+static __always_inline void
+libc_fesetround_ppc (int r)
+{
+  __fesetround_inline (r);
 }
 
 static __always_inline int
@@ -84,98 +86,67 @@ libc_fetestexcept_ppc (int e)
 }
 
 static __always_inline void
-libc_fesetenv_ppc (const fenv_t *envp)
+libc_feholdsetround_ppc (fenv_t *e, int r)
+{
+  __libc_feholdbits_ppc (e, _FPU_MASK_TRAPS_RN, r);
+}
+
+static __always_inline unsigned long long
+__libc_femergeenv_ppc (const fenv_t *envp, unsigned long long old_mask,
+	unsigned long long new_mask)
 {
   fenv_union_t old, new;
 
   new.fenv = *envp;
   old.fenv = fegetenv_register ();
 
+  /* Merge bits while masking unwanted bits from new and old env.  */
+  new.l = (old.l & old_mask) | (new.l & new_mask);
+
   /* If the old env has no enabled exceptions and the new env has any enabled
      exceptions, then unmask SIGFPE in the MSR FE0/FE1 bits.  This will put the
      hardware into "precise mode" and may cause the FPU to run slower on some
      hardware.  */
-  if ((old.l & _FPU_MASK_ALL) == 0 && (new.l & _FPU_MASK_ALL) != 0)
+  if ((old.l & _FPU_ALL_TRAPS) == 0 && (new.l & _FPU_ALL_TRAPS) != 0)
     (void) __fe_nomask_env_priv ();
 
   /* If the old env had any enabled exceptions and the new env has no enabled
      exceptions, then mask SIGFPE in the MSR FE0/FE1 bits.  This may allow the
      FPU to run faster because it always takes the default action and can not
      generate SIGFPE.  */
-  if ((old.l & _FPU_MASK_ALL) != 0 && (new.l & _FPU_MASK_ALL) == 0)
-    (void) __fe_mask_env ();
-
-  fesetenv_register (*envp);
-}
-
-static __always_inline int
-libc_feupdateenv_test_ppc (fenv_t *envp, int ex)
-{
-  fenv_union_t old, new;
-
-  new.fenv = *envp;
-  old.fenv = fegetenv_register ();
-
-  /* Restore rounding mode and exception enable from *envp and merge
-     exceptions.  Leave fraction rounded/inexact and FP result/CC bits
-     unchanged.  */
-  new.l = (old.l & _FPU_MASK_EXCEPT_ROUND)
-          | (new.l & _FPU_MASK_FRAC_INEX_RET_CC);
-
-  if ((old.l & _FPU_MASK_ALL) == 0 && (new.l & _FPU_MASK_ALL) != 0)
-    (void) __fe_nomask_env_priv ();
-
-  if ((old.l & _FPU_MASK_ALL) != 0 && (new.l & _FPU_MASK_ALL) == 0)
+  if ((old.l & _FPU_ALL_TRAPS) != 0 && (new.l & _FPU_ALL_TRAPS) == 0)
     (void) __fe_mask_env ();
 
+  /* Atomically enable and raise (if appropriate) exceptions set in `new'.  */
   fesetenv_register (new.fenv);
 
-  return old.l & ex;
+  return old.l;
 }
 
 static __always_inline void
-libc_feupdateenv_ppc (fenv_t *e)
+libc_fesetenv_ppc (const fenv_t *envp)
 {
-  libc_feupdateenv_test_ppc (e, 0);
+  /* Replace the entire environment.  */
+  __libc_femergeenv_ppc (envp, 0LL, -1LL);
 }
 
 static __always_inline void
-libc_feholdsetround_ppc (fenv_t *e, int r)
+libc_feresetround_ppc (fenv_t *envp)
 {
-  fenv_union_t old, new;
-
-  old.fenv = fegetenv_register ();
-  /* Clear current precision and set newer one.  */
-  new.l = (old.l & ~0x3 & ~_FPU_MASK_ALL) | r;
-  *e = old.fenv;
+  __libc_femergeenv_ppc (envp, _FPU_MASK_TRAPS_RN, _FPU_MASK_FRAC_INEX_RET_CC);
+}
 
-  if ((old.l & _FPU_MASK_ALL) != 0)
-    (void) __fe_mask_env ();
-  fesetenv_register (new.fenv);
+static __always_inline int
+libc_feupdateenv_test_ppc (fenv_t *envp, int ex)
+{
+  return __libc_femergeenv_ppc (envp, _FPU_MASK_TRAPS_RN,
+				_FPU_MASK_FRAC_INEX_RET_CC) & ex;
 }
 
 static __always_inline void
-libc_feresetround_ppc (fenv_t *envp)
+libc_feupdateenv_ppc (fenv_t *e)
 {
-  fenv_union_t old, new;
-
-  new.fenv = *envp;
-  old.fenv = fegetenv_register ();
-
-  /* Restore rounding mode and exception enable from *envp and merge
-     exceptions.  Leave fraction rounded/inexact and FP result/CC bits
-     unchanged.  */
-  new.l = (old.l & _FPU_MASK_EXCEPT_ROUND)
-          | (new.l & _FPU_MASK_FRAC_INEX_RET_CC);
-
-  if ((old.l & _FPU_MASK_ALL) == 0 && (new.l & _FPU_MASK_ALL) != 0)
-    (void) __fe_nomask_env_priv ();
-
-  if ((old.l & _FPU_MASK_ALL) != 0 && (new.l & _FPU_MASK_ALL) == 0)
-    (void) __fe_mask_env ();
-
-  /* Atomically enable and raise (if appropriate) exceptions set in `new'.  */
-  fesetenv_register (new.fenv);
+  libc_feupdateenv_test_ppc (e, 0);
 }
 
 #define libc_feholdexceptf           libc_feholdexcept_ppc
@@ -202,17 +173,18 @@ libc_feresetround_ppc (fenv_t *envp)
 #define HAVE_RM_CTX 1
 
 static __always_inline void
-libc_feholdexcept_setround_ppc_ctx (struct rm_ctx *ctx, int r)
+libc_feholdsetround_ppc_ctx (struct rm_ctx *ctx, int r)
 {
   fenv_union_t old, new;
 
   old.fenv = fegetenv_register ();
 
-  new.l = (old.l & _FPU_MASK_ROUNDING) | r;
+  new.l = (old.l & _FPU_MASK_TRAPS_RN) | r;
+
   ctx->env = old.fenv;
   if (__glibc_unlikely (new.l != old.l))
     {
-      if ((old.l & _FPU_MASK_ALL) != 0)
+      if ((old.l & _FPU_ALL_TRAPS) != 0)
 	(void) __fe_mask_env ();
       fesetenv_register (new.fenv);
       ctx->updated_status = true;
@@ -231,26 +203,7 @@ static __always_inline void
 libc_feupdateenv_ppc_ctx (struct rm_ctx *ctx)
 {
   if (__glibc_unlikely (ctx->updated_status))
-    libc_feupdateenv_test_ppc (&ctx->env, 0);
-}
-
-static __always_inline void
-libc_feholdsetround_ppc_ctx (struct rm_ctx *ctx, int r)
-{
-  fenv_union_t old, new;
-
-  old.fenv = fegetenv_register ();
-  new.l = (old.l & ~0x3 & ~_FPU_MASK_ALL) | r;
-  ctx->env = old.fenv;
-  if (__glibc_unlikely (new.l != old.l))
-    {
-      if ((old.l & _FPU_MASK_ALL) != 0)
-	(void) __fe_mask_env ();
-      fesetenv_register (new.fenv);
-      ctx->updated_status = true;
-    }
-  else
-    ctx->updated_status = false;
+    libc_feresetround_ppc (&ctx->env);
 }
 
 static __always_inline void
@@ -260,9 +213,6 @@ libc_feresetround_ppc_ctx (struct rm_ctx *ctx)
     libc_feresetround_ppc (&ctx->env);
 }
 
-#define libc_feholdexcept_setround_ctx   libc_feholdexcept_setround_ppc_ctx
-#define libc_feholdexcept_setroundf_ctx  libc_feholdexcept_setround_ppc_ctx
-#define libc_feholdexcept_setroundl_ctx  libc_feholdexcept_setround_ppc_ctx
 #define libc_fesetenv_ctx                libc_fesetenv_ppc_ctx
 #define libc_fesetenvf_ctx               libc_fesetenv_ppc_ctx
 #define libc_fesetenvl_ctx               libc_fesetenv_ppc_ctx