[compiler-rt] Do not use ldrexd or strexd on v7M

[olista01]

Summary

The ldrexd and strexd instructions are undefined for the ARMv7M architecture, so we cannot use them to implement the __sync_fetch_and_*_8 builtins. There is no other way to implement these without OS support, so this patch #ifdef's these functions out for M-class architectures.

There are no tests as I cannot find any existing tests for these builtins.

I used the ARM_ARCH_PROFILE predefine because ARM_FEATURE_LDREX is deprecated and not set by clang.

[rengolin]

Hi Oliver,

If these macros are not defined, wouldn't that become a compilation time error on any code that use them?

Unless they're defined by something else (OS-specific headers?), there should be an #error stating the lack of support, or some other way to help the user identify the problem earlier.

cheers,
--renato

[olista01]

The SYNC_OP_8 macro (defined in lib/builtins/arm/sync-ops.h) uses these macros to emit the __sync_fetch_and_*_8 functions, so these #ifdefs have the effect of not building any of these functions. These are builtins which are used by the compiler, so they are not in any header file. This will result in a link error if the user tries to use any 64-bit atomic operations. However, a version of this runtime library designed to be used with an operating system could provide these operations, so I don't think the compiler should error if they are used.

[rengolin]

Makes sense, LGTM. Thanks!

--renato

[olista01]

Thanks, committed as r218601.

lib/builtins/arm/sync_fetch_and_add_8.S

 /*===-- sync_fetch_and_add_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_add_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define add_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
     adds rD_LO, rN_LO, rM_LO ; \
     adc rD_HI, rN_HI, rM_HI
 
 SYNC_OP_8(add_8)
+#endif
 

lib/builtins/arm/sync_fetch_and_and_8.S

 /*===-- sync_fetch_and_and_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_and_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define and_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
     and rD_LO, rN_LO, rM_LO ; \
     and rD_HI, rN_HI, rM_HI
 
 SYNC_OP_8(and_8)
+#endif

lib/builtins/arm/sync_fetch_and_max_8.S

 /*===-- sync_fetch_and_max_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_max_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define max_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, gt)
 
 SYNC_OP_8(max_8)
+#endif

lib/builtins/arm/sync_fetch_and_min_8.S

 /*===-- sync_fetch_and_min_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_min_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define min_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, lt)
 
 SYNC_OP_8(min_8)
+#endif

lib/builtins/arm/sync_fetch_and_nand_8.S

 /*===-- sync_fetch_and_nand_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_nand_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define nand_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
     bic rD_LO, rN_LO, rM_LO ; \
     bic rD_HI, rN_HI, rM_HI
 
 SYNC_OP_8(nand_8)
+#endif
 

lib/builtins/arm/sync_fetch_and_or_8.S

 /*===-- sync_fetch_and_or_8.S - -------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_or_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define or_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
     orr rD_LO, rN_LO, rM_LO ; \
     orr rD_HI, rN_HI, rM_HI
 
 SYNC_OP_8(or_8)
+#endif
 

lib/builtins/arm/sync_fetch_and_sub_8.S

 /*===-- sync_fetch_and_sub_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_sub_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define sub_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
     subs rD_LO, rN_LO, rM_LO ; \
     sbc rD_HI, rN_HI, rM_HI
 
 SYNC_OP_8(sub_8)
+#endif
 

lib/builtins/arm/sync_fetch_and_umax_8.S

 /*===-- sync_fetch_and_umax_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_umax_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define umax_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, hi)
 
 SYNC_OP_8(umax_8)
+#endif

lib/builtins/arm/sync_fetch_and_umin_8.S

 /*===-- sync_fetch_and_umin_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_umin_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define umin_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI)         MINMAX_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI, lo)
 
 SYNC_OP_8(umin_8)
+#endif

lib/builtins/arm/sync_fetch_and_xor_8.S

 /*===-- sync_fetch_and_xor_8.S - ------------------------------------------===//
  *
  *                     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 the __sync_fetch_and_xor_8 function for the ARM
  * architecture.
  *
  *===----------------------------------------------------------------------===*/
 
 #include "sync-ops.h"
 
+#if __ARM_ARCH_PROFILE != 'M'
 #define xor_8(rD_LO, rD_HI, rN_LO, rN_HI, rM_LO, rM_HI) \
     eor rD_LO, rN_LO, rM_LO ; \
     eor rD_HI, rN_HI, rM_HI
 
 SYNC_OP_8(xor_8)
+#endif