Fix Compilation on ppc64le using Clang 11 (#7713)

Summary:
Closes facebook/rocksdb#7691

The optimised CRC code for PPC64le which was originally imported in facebook/rocksdb#2353 is not compatible with Clang 11. It looks like the code most likely originated from https://github.com/antonblanchard/crc32-vpmsum.

The code relied on a GCC header file `ppc-asm.h` which is not available in Clang.

To solve this, I have taken the same approach as the the upstream project from which the CRC code came antonblanchard/crc32-vpmsum@ffc8018#diff-ec3e62c56fbcddeb07230f2a4673c1abd7f0f1cc8e48a2aa560056cfc1b25d60 and simply imported a copy of the GCC header file into our code-base which will be used when Clang is the compiler on pcc64le.

**NOTE**: The new file `util/ppc-asm.h` may have licensing implications which I guess need to be approved by RocksDB/Facebook before this is merged

Pull Request resolved: facebook/rocksdb#7713

Reviewed By: jay-zhuang

Differential Revision: D25222645

Pulled By: pdillinger

fbshipit-source-id: e3fec9136f26ce1eb7a027048bcf77a6cb3c769c

third-party/gcc/ppc-asm.h

@@ -0,0 +1,390 @@
+/* PowerPC asm definitions for GNU C.
+
+Copyright (C) 2002-2020 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+Under Section 7 of GPL version 3, you are granted additional
+permissions described in the GCC Runtime Library Exception, version
+3.1, as published by the Free Software Foundation.
+
+You should have received a copy of the GNU General Public License and
+a copy of the GCC Runtime Library Exception along with this program;
+see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+<http://www.gnu.org/licenses/>.  */
+
+/* Under winnt, 1) gas supports the following as names and 2) in particular
+   defining "toc" breaks the FUNC_START macro as ".toc" becomes ".2" */
+
+#define r0	0
+#define sp	1
+#define toc	2
+#define r3	3
+#define r4	4
+#define r5	5
+#define r6	6
+#define r7	7
+#define r8	8
+#define r9	9
+#define r10	10
+#define r11	11
+#define r12	12
+#define r13	13
+#define r14	14
+#define r15	15
+#define r16	16
+#define r17	17
+#define r18	18
+#define r19     19
+#define r20	20
+#define r21	21
+#define r22	22
+#define r23	23
+#define r24	24
+#define r25	25
+#define r26	26
+#define r27	27
+#define r28	28
+#define r29	29
+#define r30	30
+#define r31	31
+
+#define cr0	0
+#define cr1	1
+#define cr2	2
+#define cr3	3
+#define cr4	4
+#define cr5	5
+#define cr6	6
+#define cr7	7
+
+#define f0	0
+#define f1	1
+#define f2	2
+#define f3	3
+#define f4	4
+#define f5	5
+#define f6	6
+#define f7	7
+#define f8	8
+#define f9	9
+#define f10	10
+#define f11	11
+#define f12	12
+#define f13	13
+#define f14	14
+#define f15	15
+#define f16	16
+#define f17	17
+#define f18	18
+#define f19	19
+#define f20	20
+#define f21	21
+#define f22	22
+#define f23	23
+#define f24	24
+#define f25	25
+#define f26	26
+#define f27	27
+#define f28	28
+#define f29	29
+#define f30	30
+#define f31	31
+
+#ifdef __VSX__
+#define f32	32
+#define f33	33
+#define f34	34
+#define f35	35
+#define f36	36
+#define f37	37
+#define f38	38
+#define f39	39
+#define f40	40
+#define f41	41
+#define f42	42
+#define f43	43
+#define f44	44
+#define f45	45
+#define f46	46
+#define f47	47
+#define f48	48
+#define f49	49
+#define f50	50
+#define f51	51
+#define f52	52
+#define f53	53
+#define f54	54
+#define f55	55
+#define f56	56
+#define f57	57
+#define f58	58
+#define f59	59
+#define f60	60
+#define f61	61
+#define f62	62
+#define f63	63
+#endif
+
+#ifdef __ALTIVEC__
+#define v0	0
+#define v1	1
+#define v2	2
+#define v3	3
+#define v4	4
+#define v5	5
+#define v6	6
+#define v7	7
+#define v8	8
+#define v9	9
+#define v10	10
+#define v11	11
+#define v12	12
+#define v13	13
+#define v14	14
+#define v15	15
+#define v16	16
+#define v17	17
+#define v18	18
+#define v19	19
+#define v20	20
+#define v21	21
+#define v22	22
+#define v23	23
+#define v24	24
+#define v25	25
+#define v26	26
+#define v27	27
+#define v28	28
+#define v29	29
+#define v30	30
+#define v31	31
+#endif
+
+#ifdef __VSX__
+#define vs0	0
+#define vs1	1
+#define vs2	2
+#define vs3	3
+#define vs4	4
+#define vs5	5
+#define vs6	6
+#define vs7	7
+#define vs8	8
+#define vs9	9
+#define vs10	10
+#define vs11	11
+#define vs12	12
+#define vs13	13
+#define vs14	14
+#define vs15	15
+#define vs16	16
+#define vs17	17
+#define vs18	18
+#define vs19	19
+#define vs20	20
+#define vs21	21
+#define vs22	22
+#define vs23	23
+#define vs24	24
+#define vs25	25
+#define vs26	26
+#define vs27	27
+#define vs28	28
+#define vs29	29
+#define vs30	30
+#define vs31	31
+#define vs32	32
+#define vs33	33
+#define vs34	34
+#define vs35	35
+#define vs36	36
+#define vs37	37
+#define vs38	38
+#define vs39	39
+#define vs40	40
+#define vs41	41
+#define vs42	42
+#define vs43	43
+#define vs44	44
+#define vs45	45
+#define vs46	46
+#define vs47	47
+#define vs48	48
+#define vs49	49
+#define vs50	50
+#define vs51	51
+#define vs52	52
+#define vs53	53
+#define vs54	54
+#define vs55	55
+#define vs56	56
+#define vs57	57
+#define vs58	58
+#define vs59	59
+#define vs60	60
+#define vs61	61
+#define vs62	62
+#define vs63	63
+#endif
+
+/*
+ * Macros to glue together two tokens.
+ */
+
+#ifdef __STDC__
+#define XGLUE(a,b) a##b
+#else
+#define XGLUE(a,b) a/**/b
+#endif
+
+#define GLUE(a,b) XGLUE(a,b)
+
+/*
+ * Macros to begin and end a function written in assembler.  If -mcall-aixdesc
+ * or -mcall-nt, create a function descriptor with the given name, and create
+ * the real function with one or two leading periods respectively.
+ */
+
+#if defined(__powerpc64__) && _CALL_ELF == 2
+
+/* Defining "toc" above breaks @toc in assembler code.  */
+#undef toc
+
+#define FUNC_NAME(name) GLUE(__USER_LABEL_PREFIX__,name)
+#ifdef __PCREL__
+#define JUMP_TARGET(name) GLUE(FUNC_NAME(name),@notoc)
+#define FUNC_START(name) \
+	.type FUNC_NAME(name),@function; \
+	.globl FUNC_NAME(name); \
+FUNC_NAME(name): \
+	.localentry FUNC_NAME(name),1
+#else
+#define JUMP_TARGET(name) FUNC_NAME(name)
+#define FUNC_START(name) \
+	.type FUNC_NAME(name),@function; \
+	.globl FUNC_NAME(name); \
+FUNC_NAME(name): \
+0:	addis 2,12,(.TOC.-0b)@ha; \
+	addi 2,2,(.TOC.-0b)@l; \
+	.localentry FUNC_NAME(name),.-FUNC_NAME(name)
+#endif /* !__PCREL__ */
+
+#define HIDDEN_FUNC(name) \
+  FUNC_START(name) \
+  .hidden FUNC_NAME(name);
+
+#define FUNC_END(name) \
+	.size FUNC_NAME(name),.-FUNC_NAME(name)
+
+#elif defined (__powerpc64__)
+
+#define FUNC_NAME(name) GLUE(.,name)
+#define JUMP_TARGET(name) FUNC_NAME(name)
+#define FUNC_START(name) \
+	.section ".opd","aw"; \
+name: \
+	.quad GLUE(.,name); \
+	.quad .TOC.@tocbase; \
+	.quad 0; \
+	.previous; \
+	.type GLUE(.,name),@function; \
+	.globl name; \
+	.globl GLUE(.,name); \
+GLUE(.,name):
+
+#define HIDDEN_FUNC(name) \
+  FUNC_START(name) \
+  .hidden name;	\
+  .hidden GLUE(.,name);
+
+#define FUNC_END(name) \
+GLUE(.L,name): \
+	.size GLUE(.,name),GLUE(.L,name)-GLUE(.,name)
+
+#elif defined(_CALL_AIXDESC)
+
+#ifdef _RELOCATABLE
+#define DESC_SECTION ".got2"
+#else
+#define DESC_SECTION ".got1"
+#endif
+
+#define FUNC_NAME(name) GLUE(.,name)
+#define JUMP_TARGET(name) FUNC_NAME(name)
+#define FUNC_START(name) \
+	.section DESC_SECTION,"aw"; \
+name: \
+	.long GLUE(.,name); \
+	.long _GLOBAL_OFFSET_TABLE_; \
+	.long 0; \
+	.previous; \
+	.type GLUE(.,name),@function; \
+	.globl name; \
+	.globl GLUE(.,name); \
+GLUE(.,name):
+
+#define HIDDEN_FUNC(name) \
+  FUNC_START(name) \
+  .hidden name; \
+  .hidden GLUE(.,name);
+
+#define FUNC_END(name) \
+GLUE(.L,name): \
+	.size GLUE(.,name),GLUE(.L,name)-GLUE(.,name)
+
+#else
+
+#define FUNC_NAME(name) GLUE(__USER_LABEL_PREFIX__,name)
+#if defined __PIC__ || defined __pic__
+#define JUMP_TARGET(name) FUNC_NAME(name@plt)
+#else
+#define JUMP_TARGET(name) FUNC_NAME(name)
+#endif
+#define FUNC_START(name) \
+	.type FUNC_NAME(name),@function; \
+	.globl FUNC_NAME(name); \
+FUNC_NAME(name):
+
+#define HIDDEN_FUNC(name) \
+  FUNC_START(name) \
+  .hidden FUNC_NAME(name);
+
+#define FUNC_END(name) \
+GLUE(.L,name): \
+	.size FUNC_NAME(name),GLUE(.L,name)-FUNC_NAME(name)
+#endif
+
+#ifdef IN_GCC
+/* For HAVE_GAS_CFI_DIRECTIVE.  */
+#include "auto-host.h"
+
+#ifdef HAVE_GAS_CFI_DIRECTIVE
+# define CFI_STARTPROC			.cfi_startproc
+# define CFI_ENDPROC			.cfi_endproc
+# define CFI_OFFSET(reg, off)		.cfi_offset reg, off
+# define CFI_DEF_CFA_REGISTER(reg)	.cfi_def_cfa_register reg
+# define CFI_RESTORE(reg)		.cfi_restore reg
+#else
+# define CFI_STARTPROC
+# define CFI_ENDPROC
+# define CFI_OFFSET(reg, off)
+# define CFI_DEF_CFA_REGISTER(reg)
+# define CFI_RESTORE(reg)
+#endif
+#endif
+
+#if defined __linux__ && !defined __powerpc64__
+	.section .note.GNU-stack
+	.previous
+#endif