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author | Alexey Samsonov <samsonov@google.com> | 2014-02-14 09:20:33 +0000 |
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committer | Alexey Samsonov <samsonov@google.com> | 2014-02-14 09:20:33 +0000 |
commit | 53aa4fda49f94920139300227786ac47c393f1ce (patch) | |
tree | 6d022d04ee279fe1afd89668f346e28a9e3e1559 /lib/builtins/arm/clzdi2.S | |
parent | 6d999e478fecb10dc43f20b85385d25cc239db0a (diff) |
Move original compiler-rt functions (libgcc replacement) to lib/builtins directory
git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@201393 91177308-0d34-0410-b5e6-96231b3b80d8
Diffstat (limited to 'lib/builtins/arm/clzdi2.S')
-rw-r--r-- | lib/builtins/arm/clzdi2.S | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/lib/builtins/arm/clzdi2.S b/lib/builtins/arm/clzdi2.S new file mode 100644 index 000000000..33284cd3a --- /dev/null +++ b/lib/builtins/arm/clzdi2.S @@ -0,0 +1,89 @@ +/* ===-- clzdi2.c - Implement __clzdi2 -------------------------------------=== + * + * The LLVM Compiler Infrastructure + * + * This file is dual licensed under the MIT and the University of Illinois Open + * Source Licenses. See LICENSE.TXT for details. + * + * ===----------------------------------------------------------------------=== + * + * This file implements count leading zeros for 64bit arguments. + * + * ===----------------------------------------------------------------------=== + */ +#include "../assembly.h" + + .syntax unified + + .text + .align 2 +DEFINE_COMPILERRT_FUNCTION(__clzdi2) +#ifdef __ARM_FEATURE_CLZ +#ifdef __ARMEB__ + cmp r0, 0 + itee ne + clzne r0, r0 + clzeq r0, r1 + addeq r0, r0, 32 +#else + cmp r1, 0 + itee ne + clzne r0, r1 + clzeq r0, r0 + addeq r0, r0, 32 +#endif + JMP(lr) +#else + /* Assumption: n != 0 */ + + /* + * r0: n + * r1: upper half of n, overwritten after check + * r1: count of leading zeros in n + 1 + * r2: scratch register for shifted r0 + */ +#ifdef __ARMEB__ + cmp r0, 0 + moveq r0, r1 +#else + cmp r1, 0 + movne r0, r1 +#endif + movne r1, 1 + moveq r1, 33 + + /* + * Basic block: + * if ((r0 >> SHIFT) == 0) + * r1 += SHIFT; + * else + * r0 >>= SHIFT; + * for descending powers of two as SHIFT. + */ +#define BLOCK(shift) \ + lsrs r2, r0, shift; \ + movne r0, r2; \ + addeq r1, shift \ + + BLOCK(16) + BLOCK(8) + BLOCK(4) + BLOCK(2) + + /* + * The basic block invariants at this point are (r0 >> 2) == 0 and + * r0 != 0. This means 1 <= r0 <= 3 and 0 <= (r0 >> 1) <= 1. + * + * r0 | (r0 >> 1) == 0 | (r0 >> 1) == 1 | -(r0 >> 1) | 1 - (r0 >> 1) + * ---+----------------+----------------+------------+-------------- + * 1 | 1 | 0 | 0 | 1 + * 2 | 0 | 1 | -1 | 0 + * 3 | 0 | 1 | -1 | 0 + * + * The r1's initial value of 1 compensates for the 1 here. + */ + sub r0, r1, r0, lsr #1 + + JMP(lr) +#endif // __ARM_FEATURE_CLZ +END_COMPILERRT_FUNCTION(__clzdi2) |