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[PATCH] [powerpc] fe{en,dis}ableexcept optimize bit translations
- From: "Paul A. Clarke" <pc at us dot ibm dot com>
- To: libc-alpha at sourceware dot org
- Cc: tuliom at ascii dot art dot br, murphyp at linux dot ibm dot com
- Date: Fri, 2 Aug 2019 23:22:33 -0400
- Subject: [PATCH] [powerpc] fe{en,dis}ableexcept optimize bit translations
From: "Paul A. Clarke" <pc@us.ibm.com>
The exceptions passed to fe{en,dis}ableexcept() are defined in the ABI
as a bitmask, a combination of FE_INVALID, FE_OVERFLOW, etc.
Within the functions, these bits must be translated to/from the corresponding
enable bits in the Floating Point Status Control Register (FPSCR).
This translation is currently done bit-by-bit. The compiler generates
a series of conditional bit operations. Nicely, the "FE" exception
bits are all a uniform offset from the FPSCR enable bits, so the bit-by-bit
operation can instead be performed by a shift with appropriate masking.
2019-08-02 Paul A. Clarke <pc@us.ibm.com>
* sysdeps/powerpc/fpu/fenv_libc.h: Define FPSCR bitmasks.
(fenv_reg_to_exceptions): Replace bitwise operations with mask-shift.
(fenv_exceptions_to_reg): New.
* sysdeps/powerpc/fpu/fedisblxcpt.c (fedisableexcept): Replace bitwise
operation with call to fenv_exceptions_to_reg().
* sysdeps/powerpc/fpu/feenablxcpt.c (feenableexcept): Likewise.
This patch is a prerequisite for the two patches I sent over the past two days:
- [powerpc] fe{en,dis}ableexcept, fesetmode: optimize FPSCR accesses
- [powerpc] SET_RESTORE_ROUND improvements
Apologies for sending these out-of-order. I forgot about this one during the
freeze window.
---
sysdeps/powerpc/fpu/fedisblxcpt.c | 11 +-----
sysdeps/powerpc/fpu/feenablxcpt.c | 11 +-----
sysdeps/powerpc/fpu/fenv_libc.h | 72 ++++++++++++++++++++++++++++++++-------
3 files changed, 61 insertions(+), 33 deletions(-)
diff --git a/sysdeps/powerpc/fpu/fedisblxcpt.c b/sysdeps/powerpc/fpu/fedisblxcpt.c
index 2872b1b..5cc8799 100644
--- a/sysdeps/powerpc/fpu/fedisblxcpt.c
+++ b/sysdeps/powerpc/fpu/fedisblxcpt.c
@@ -33,16 +33,7 @@ fedisableexcept (int excepts)
excepts = (excepts | FE_INVALID) & ~ FE_ALL_INVALID;
/* Sets the new exception mask. */
- if (excepts & FE_INEXACT)
- fe.l &= ~(1 << (31 - FPSCR_XE));
- if (excepts & FE_DIVBYZERO)
- fe.l &= ~(1 << (31 - FPSCR_ZE));
- if (excepts & FE_UNDERFLOW)
- fe.l &= ~(1 << (31 - FPSCR_UE));
- if (excepts & FE_OVERFLOW)
- fe.l &= ~(1 << (31 - FPSCR_OE));
- if (excepts & FE_INVALID)
- fe.l &= ~(1 << (31 - FPSCR_VE));
+ fe.l &= ~ fenv_exceptions_to_reg (excepts);
if (fe.l != curr.l)
fesetenv_register (fe.fenv);
diff --git a/sysdeps/powerpc/fpu/feenablxcpt.c b/sysdeps/powerpc/fpu/feenablxcpt.c
index dbaffdc..3b64398 100644
--- a/sysdeps/powerpc/fpu/feenablxcpt.c
+++ b/sysdeps/powerpc/fpu/feenablxcpt.c
@@ -33,16 +33,7 @@ feenableexcept (int excepts)
excepts = (excepts | FE_INVALID) & ~ FE_ALL_INVALID;
/* Sets the new exception mask. */
- if (excepts & FE_INEXACT)
- fe.l |= (1 << (31 - FPSCR_XE));
- if (excepts & FE_DIVBYZERO)
- fe.l |= (1 << (31 - FPSCR_ZE));
- if (excepts & FE_UNDERFLOW)
- fe.l |= (1 << (31 - FPSCR_UE));
- if (excepts & FE_OVERFLOW)
- fe.l |= (1 << (31 - FPSCR_OE));
- if (excepts & FE_INVALID)
- fe.l |= (1 << (31 - FPSCR_VE));
+ fe.l |= fenv_exceptions_to_reg (excepts);
if (fe.l != curr.l)
fesetenv_register (fe.fenv);
diff --git a/sysdeps/powerpc/fpu/fenv_libc.h b/sysdeps/powerpc/fpu/fenv_libc.h
index 9861f18..853239f 100644
--- a/sysdeps/powerpc/fpu/fenv_libc.h
+++ b/sysdeps/powerpc/fpu/fenv_libc.h
@@ -131,57 +131,103 @@ __fesetround_inline_nocheck (const int round)
/* Definitions of all the FPSCR bit numbers */
enum {
FPSCR_FX = 0, /* exception summary */
+#define FPSCR_FX_MASK (1 << (31 - FPSCR_FX))
FPSCR_FEX, /* enabled exception summary */
+#define FPSCR_FEX_MASK (1 << (31 - FPSCR_FEX))
FPSCR_VX, /* invalid operation summary */
+#define FPSCR_VX_MASK (1 << (31 - FPSCR_VX))
FPSCR_OX, /* overflow */
+#define FPSCR_OX_MASK (1 << (31 - FPSCR_OX))
FPSCR_UX, /* underflow */
+#define FPSCR_UX_MASK (1 << (31 - FPSCR_UX))
FPSCR_ZX, /* zero divide */
+#define FPSCR_ZX_MASK (1 << (31 - FPSCR_ZX))
FPSCR_XX, /* inexact */
+#define FPSCR_XX_MASK (1 << (31 - FPSCR_XX))
FPSCR_VXSNAN, /* invalid operation for sNaN */
+#define FPSCR_VXSNAN_MASK (1 << (31 - FPSCR_VXSNAN))
FPSCR_VXISI, /* invalid operation for Inf-Inf */
+#define FPSCR_VXISI_MASK (1 << (31 - FPSCR_VXISI))
FPSCR_VXIDI, /* invalid operation for Inf/Inf */
+#define FPSCR_VXIDI_MASK (1 << (31 - FPSCR_VXIDI))
FPSCR_VXZDZ, /* invalid operation for 0/0 */
+#define FPSCR_VXZDZ_MASK (1 << (31 - FPSCR_VXZDZ))
FPSCR_VXIMZ, /* invalid operation for Inf*0 */
+#define FPSCR_VXIMZ_MASK (1 << (31 - FPSCR_VXIMZ))
FPSCR_VXVC, /* invalid operation for invalid compare */
+#define FPSCR_VXVC_MASK (1 << (31 - FPSCR_VXVC))
FPSCR_FR, /* fraction rounded [fraction was incremented by round] */
+#define FPSCR_FR_MASK (1 << (31 - FPSCR_FR))
FPSCR_FI, /* fraction inexact */
+#define FPSCR_FI_MASK (1 << (31 - FPSCR_FI))
FPSCR_FPRF_C, /* result class descriptor */
+#define FPSCR_FPRF_C_MASK (1 << (31 - FPSCR_FPRF_C))
FPSCR_FPRF_FL, /* result less than (usually, less than 0) */
+#define FPSCR_FPRF_FL_MASK (1 << (31 - FPSCR_FPRF_FL))
FPSCR_FPRF_FG, /* result greater than */
+#define FPSCR_FPRF_FG_MASK (1 << (31 - FPSCR_FPRF_FG))
FPSCR_FPRF_FE, /* result equal to */
+#define FPSCR_FPRF_FE_MASK (1 << (31 - FPSCR_FPRF_FE))
FPSCR_FPRF_FU, /* result unordered */
+#define FPSCR_FPRF_FU_MASK (1 << (31 - FPSCR_FPRF_FU))
FPSCR_20, /* reserved */
FPSCR_VXSOFT, /* invalid operation set by software */
+#define FPSCR_VXSOFT_MASK (1 << (31 - FPSCR_VXSOFT))
FPSCR_VXSQRT, /* invalid operation for square root */
+#define FPSCR_VXSQRT_MASK (1 << (31 - FPSCR_VXSQRT))
FPSCR_VXCVI, /* invalid operation for invalid integer convert */
+#define FPSCR_VXCVI_MASK (1 << (31 - FPSCR_VXCVI))
FPSCR_VE, /* invalid operation exception enable */
+#define FPSCR_VE_MASK (1 << (31 - FPSCR_VE))
FPSCR_OE, /* overflow exception enable */
+#define FPSCR_OE_MASK (1 << (31 - FPSCR_OE))
FPSCR_UE, /* underflow exception enable */
+#define FPSCR_UE_MASK (1 << (31 - FPSCR_UE))
FPSCR_ZE, /* zero divide exception enable */
+#define FPSCR_ZE_MASK (1 << (31 - FPSCR_ZE))
FPSCR_XE, /* inexact exception enable */
+#define FPSCR_XE_MASK (1 << (31 - FPSCR_XE))
#ifdef _ARCH_PWR6
FPSCR_29, /* Reserved in ISA 2.05 */
+#define FPSCR_NI_MASK (1 << (31 - FPSCR_29))
#else
- FPSCR_NI /* non-IEEE mode (typically, no denormalised numbers) */
+ FPSCR_NI, /* non-IEEE mode (typically, no denormalised numbers) */
+#define FPSCR_NI_MASK (1 << (31 - FPSCR_NI))
#endif /* _ARCH_PWR6 */
/* the remaining two least-significant bits keep the rounding mode */
+ FPSCR_RN_hi,
+#define FPSCR_RN_hi_MASK (1 << (31 - FPSCR_RN_hi))
+ FPSCR_RN_lo
+#define FPSCR_RN_lo_MASK (1 << (31 - FPSCR_RN_lo))
};
+#define FPSCR_RN_MASK (FPSCR_RN_hi_MASK|FPSCR_RN_lo_MASK)
+#define FPSCR_ENABLES_MASK \
+ (FPSCR_VE_MASK|FPSCR_OE_MASK|FPSCR_UE_MASK|FPSCR_ZE_MASK|FPSCR_XE_MASK)
+#define FPSCR_BASIC_EXCEPTIONS_MASK \
+ (FPSCR_VX_MASK|FPSCR_OX_MASK|FPSCR_UX_MASK|FPSCR_ZX_MASK|FPSCR_XX_MASK)
+
+#define FPSCR_CONTROL_MASK (FPSCR_ENABLES_MASK|FPSCR_NI_MASK|FPSCR_RN_MASK)
+
+/* The bits in the FENV(1) ABI for exceptions correspond one-to-one with bits
+ in the FPSCR, albeit shifted to different but corresponding locations.
+ Similarly, the exception indicator bits in the FPSCR correspond one-to-one
+ with the exception enable bits. It is thus possible to map the FENV(1)
+ exceptions directly to the FPSCR enables with a simple mask and shift,
+ and vice versa. */
+#define FPSCR_EXCEPT_TO_ENABLE_SHIFT 22
+
static inline int
fenv_reg_to_exceptions (unsigned long long l)
{
- int result = 0;
- if (l & (1 << (31 - FPSCR_XE)))
- result |= FE_INEXACT;
- if (l & (1 << (31 - FPSCR_ZE)))
- result |= FE_DIVBYZERO;
- if (l & (1 << (31 - FPSCR_UE)))
- result |= FE_UNDERFLOW;
- if (l & (1 << (31 - FPSCR_OE)))
- result |= FE_OVERFLOW;
- if (l & (1 << (31 - FPSCR_VE)))
- result |= FE_INVALID;
- return result;
+ return (((int)l) & FPSCR_ENABLES_MASK) << FPSCR_EXCEPT_TO_ENABLE_SHIFT;
+}
+
+static inline unsigned long long
+fenv_exceptions_to_reg (int excepts)
+{
+ return (unsigned long long)
+ (excepts & FE_ALL_EXCEPT) >> FPSCR_EXCEPT_TO_ENABLE_SHIFT;
}
#ifdef _ARCH_PWR6
--
1.8.3.1