From: Daniel Engel <gnu@danielengel.com>
To: Richard Earnshaw <Richard.Earnshaw@foss.arm.com>,
gcc-patches@gcc.gnu.org
Cc: Daniel Engel <gnu@danielengel.com>,
Christophe Lyon <christophe.lyon@linaro.org>
Subject: [PATCH v7 12/34] Import 'clrsb' functions from the CM0 library
Date: Mon, 31 Oct 2022 08:45:07 -0700 [thread overview]
Message-ID: <20221031154529.3627576-13-gnu@danielengel.com> (raw)
In-Reply-To: <20221031154529.3627576-1-gnu@danielengel.com>
This implementation provides an efficient tail call to __clzsi2(), making the
functions rather smaller and faster than the C versions.
gcc/libgcc/ChangeLog:
2022-10-09 Daniel Engel <gnu@danielengel.com>
* config/arm/bits/clz2.S (__clrsbsi2, __clrsbdi2):
Added new functions.
* config/arm/t-elf (LIB1ASMFUNCS):
Added new function objects _clrsbsi2 and _clrsbdi2).
---
libgcc/config/arm/clz2.S | 108 ++++++++++++++++++++++++++++++++++++++-
libgcc/config/arm/t-elf | 2 +
2 files changed, 108 insertions(+), 2 deletions(-)
diff --git a/libgcc/config/arm/clz2.S b/libgcc/config/arm/clz2.S
index ed04698fef4..3d40811278b 100644
--- a/libgcc/config/arm/clz2.S
+++ b/libgcc/config/arm/clz2.S
@@ -1,4 +1,4 @@
-/* clz2.S: Cortex M0 optimized 'clz' functions
+/* clz2.S: ARM optimized 'clz' and related functions
Copyright (C) 2018-2022 Free Software Foundation, Inc.
Contributed by Daniel Engel (gnu@danielengel.com)
@@ -23,7 +23,7 @@
<http://www.gnu.org/licenses/>. */
-#if defined(__ARM_FEATURE_CLZ) && __ARM_FEATURE_CLZ
+#ifdef __ARM_FEATURE_CLZ
#ifdef L_clzdi2
@@ -242,3 +242,107 @@ FUNC_END clzdi2
#endif /* !__ARM_FEATURE_CLZ */
+
+#ifdef L_clrsbdi2
+
+// int __clrsbdi2(int)
+// Counts the number of "redundant sign bits" in $r1:$r0.
+// Returns the result in $r0.
+// Uses $r2 and $r3 as scratch space.
+FUNC_START_SECTION clrsbdi2 .text.sorted.libgcc.clz2.clrsbdi2
+ CFI_START_FUNCTION
+
+ #if defined(__ARM_FEATURE_CLZ) && __ARM_FEATURE_CLZ
+ // Invert negative signs to keep counting zeros.
+ asrs r3, xxh, #31
+ eors xxl, r3
+ eors xxh, r3
+
+ // Same as __clzdi2(), except that the 'C' flag is pre-calculated.
+ // Also, the trailing 'subs', since the last bit is not redundant.
+ do_it eq, et
+ clzeq r0, xxl
+ clzne r0, xxh
+ addeq r0, #32
+ subs r0, #1
+ RET
+
+ #else /* !__ARM_FEATURE_CLZ */
+ // Result if all the bits in the argument are zero.
+ // Set it here to keep the flags clean after 'eors' below.
+ movs r2, #31
+
+ // Invert negative signs to keep counting zeros.
+ asrs r3, xxh, #31
+ eors xxh, r3
+
+ #if defined(__ARMEB__) && __ARMEB__
+ // If the upper word is non-zero, return '__clzsi2(upper) - 1'.
+ bne SYM(__internal_clzsi2)
+
+ // The upper word is zero, prepare the lower word.
+ movs r0, r1
+ eors r0, r3
+
+ #else /* !__ARMEB__ */
+ // Save the lower word temporarily.
+ // This somewhat awkward construction adds one cycle when the
+ // branch is not taken, but prevents a double-branch.
+ eors r3, r0
+
+ // If the upper word is non-zero, return '__clzsi2(upper) - 1'.
+ movs r0, r1
+ bne SYM(__internal_clzsi2)
+
+ // Restore the lower word.
+ movs r0, r3
+
+ #endif /* !__ARMEB__ */
+
+ // The upper word is zero, return '31 + __clzsi2(lower)'.
+ adds r2, #32
+ b SYM(__internal_clzsi2)
+
+ #endif /* !__ARM_FEATURE_CLZ */
+
+ CFI_END_FUNCTION
+FUNC_END clrsbdi2
+
+#endif /* L_clrsbdi2 */
+
+
+#ifdef L_clrsbsi2
+
+// int __clrsbsi2(int)
+// Counts the number of "redundant sign bits" in $r0.
+// Returns the result in $r0.
+// Uses $r2 and possibly $r3 as scratch space.
+FUNC_START_SECTION clrsbsi2 .text.sorted.libgcc.clz2.clrsbsi2
+ CFI_START_FUNCTION
+
+ // Invert negative signs to keep counting zeros.
+ asrs r2, r0, #31
+ eors r0, r2
+
+ #if defined(__ARM_FEATURE_CLZ) && __ARM_FEATURE_CLZ
+ // Count.
+ clz r0, r0
+
+ // The result for a positive value will always be >= 1.
+ // By definition, the last bit is not redundant.
+ subs r0, #1
+ RET
+
+ #else /* !__ARM_FEATURE_CLZ */
+ // Result if all the bits in the argument are zero.
+ // By definition, the last bit is not redundant.
+ movs r2, #31
+ b SYM(__internal_clzsi2)
+
+ #endif /* !__ARM_FEATURE_CLZ */
+
+ CFI_END_FUNCTION
+FUNC_END clrsbsi2
+
+#endif /* L_clrsbsi2 */
+
diff --git a/libgcc/config/arm/t-elf b/libgcc/config/arm/t-elf
index 33b83ac4adf..89071cebe45 100644
--- a/libgcc/config/arm/t-elf
+++ b/libgcc/config/arm/t-elf
@@ -31,6 +31,8 @@ LIB1ASMFUNCS += \
_ashldi3 \
_ashrdi3 \
_lshrdi3 \
+ _clrsbsi2 \
+ _clrsbdi2 \
_clzdi2 \
_ctzdi2 \
_dvmd_tls \
--
2.34.1
next prev parent reply other threads:[~2022-10-31 15:47 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-31 15:44 [PATCH v7 00/34] libgcc: Thumb-1 Floating-Point Assembly for Cortex M0 Daniel Engel
2022-10-31 15:44 ` [PATCH v7 01/34] Add and restructure function declaration macros Daniel Engel
2022-10-31 15:44 ` [PATCH v7 02/34] Rename THUMB_FUNC_START to THUMB_FUNC_ENTRY Daniel Engel
2022-10-31 15:44 ` [PATCH v7 03/34] Fix syntax warnings on conditional instructions Daniel Engel
2022-10-31 15:44 ` [PATCH v7 04/34] Reorganize LIB1ASMFUNCS object wrapper macros Daniel Engel
2022-10-31 15:45 ` [PATCH v7 05/34] Add the __HAVE_FEATURE_IT and IT() macros Daniel Engel
2022-10-31 15:45 ` [PATCH v7 06/34] Refactor 'clz' functions into a new file Daniel Engel
2022-10-31 15:45 ` [PATCH v7 07/34] Refactor 'ctz' " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 08/34] Refactor 64-bit shift " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 09/34] Import 'clz' functions from the CM0 library Daniel Engel
2022-10-31 15:45 ` [PATCH v7 10/34] Import 'ctz' " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 11/34] Import 64-bit shift " Daniel Engel
2022-10-31 15:45 ` Daniel Engel [this message]
2022-10-31 15:45 ` [PATCH v7 13/34] Import 'ffs' " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 14/34] Import 'parity' " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 15/34] Import 'popcnt' " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 16/34] Refactor Thumb-1 64-bit comparison into a new file Daniel Engel
2022-10-31 15:45 ` [PATCH v7 17/34] Import 64-bit comparison from CM0 library Daniel Engel
2022-10-31 15:45 ` [PATCH v7 18/34] Merge Thumb-2 optimizations for 64-bit comparison Daniel Engel
2022-10-31 15:45 ` [PATCH v7 19/34] Import 32-bit division from the CM0 library Daniel Engel
2022-10-31 15:45 ` [PATCH v7 20/34] Refactor Thumb-1 64-bit division into a new file Daniel Engel
2022-10-31 15:45 ` [PATCH v7 21/34] Import 64-bit division from the CM0 library Daniel Engel
2022-10-31 15:45 ` [PATCH v7 22/34] Import integer multiplication " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 23/34] Refactor Thumb-1 float comparison into a new file Daniel Engel
2022-10-31 15:45 ` [PATCH v7 24/34] Import float comparison from the CM0 library Daniel Engel
2022-10-31 15:45 ` [PATCH v7 25/34] Refactor Thumb-1 float subtraction into a new file Daniel Engel
2022-10-31 15:45 ` [PATCH v7 26/34] Import float addition and subtraction from the CM0 library Daniel Engel
2022-10-31 15:45 ` [PATCH v7 27/34] Import float multiplication " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 28/34] Import float division " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 29/34] Import integer-to-float conversion " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 30/34] Import float-to-integer " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 31/34] Import float<->double " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 32/34] Import float<->__fp16 " Daniel Engel
2022-10-31 15:45 ` [PATCH v7 33/34] Drop single-precision Thumb-1 soft-float functions Daniel Engel
2022-10-31 15:45 ` [PATCH v7 34/34] Add -mpure-code support to the CM0 functions Daniel Engel
2022-11-15 15:27 ` [PING] Re: [PATCH v7 00/34] libgcc: Thumb-1 Floating-Point Assembly for Cortex M0 Daniel Engel
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