Language extension compatibility: intrinsics

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4.4 Language extension compatibility: intrinsics

Arm^® Compiler 6 provides support for some intrinsics that are supported in Arm Compiler 5.

The following table lists some of the commonly used intrinsics that are supported by Arm Compiler 5 and shows whether Arm Compiler 6 supports them or provides an alternative. If there is no support in Arm Compiler 6, you must replace them with suitable inline assembly instructions or calls to the standard library. To use the intrinsic in Arm Compiler 6, you must include the appropriate header file. The ACLE intrinsics that are supported by Arm Compiler 5 are described in the Arm^® C Language Extensions 2.1. For more information on the ACLE intrinsics that are supported by Arm Compiler 6, see the latest Arm^® C Language Extensions.

Note:

This is not an exhaustive list of all the intrinsics.
The intrinsics provided in <arm_compat.h> are only supported for AArch32.

Table 4-6 Compiler intrinsic support in Arm Compiler 6

Intrinsic in Arm Compiler 5	Function	Support in Arm Compiler 6	Header file for Arm Compiler 6
`__breakpoint`	Inserts a `BKPT` instruction.	Yes	`arm_compat.h`
`__cdp`	Inserts a coprocessor instruction.	Yes. In Arm Compiler 6, the equivalent intrinsic is `__arm_cdp`.	`arm_acle.h`
`__clrex`	Inserts a `CLREX` instruction.	No	-
`__clz`	Inserts a `CLZ` instruction or equivalent routine.	Yes	`arm_acle.h`
`__current_pc`	Returns the program counter at this point.	Yes	`arm_compat.h`
`__current_sp`	Returns the stack pointer at this point.	Yes	`arm_compat.h`
`__isb`	Inserts `ISB` or equivalent.	Yes	`arm_acle.h`
`__disable_fiq`	Disables FIQ interrupts (Armv7 architecture only). Returns previous value of FIQ mask.	Yes	`arm_compat.h`
`__disable_irq`	Disable IRQ interrupts. Returns previous value of IRQ mask.	Yes	`arm_compat.h`
`__dmb`	Inserts a `DMB` instruction or equivalent.	Yes	`arm_acle.h`
`__dsb`	Inserts a `DSB` instruction or equivalent.	Yes	`arm_acle.h`
`__enable_fiq`	Enables fast interrupts.	Yes	`arm_compat.h`
`__enable_irq`	Enables IRQ interrupts.	Yes	`arm_compat.h`
`__fabs`	Inserts a `VABS` or equivalent code sequence.	No. Arm recommends using the standard C library function `fabs()`.	-
`__fabsf`	Single precision version of `__fabs`.	No. Arm recommends using the standard C library function `fabsf()`.	-
`__force_stores`	Flushes all external variables visible from this function, if they have been changed.	Yes	`arm_compat.h`
`__ldrex`	Inserts an appropriately sized Load Exclusive instruction.	No. This intrinsic is deprecated in ACLE 2.0.	-
`__ldrexd`	Inserts an `LDREXD` instruction.	No. This intrinsic is deprecated in ACLE 2.0.	-
`__ldrt`	Inserts an appropriately sized user-mode load instruction.	No	-
`__memory_changed`	Is similar to `__force_stores`, but also reloads the values from memory.	Yes	`arm_compat.h`
`__nop`	Inserts a `NOP` or equivalent instruction that will not be optimized away. It also inserts a sequence point, and scheduling barrier for side-effecting function calls.	Yes	`arm_acle.h`
`__pld`	Inserts a PLD instruction, if supported.	Yes	`arm_acle.h`
`__pldw`	Inserts a `PLDW` instruction, if supported (Armv7 architecture with MP).	No. Arm recommends using `__pldx` described in the ACLE document.	`arm_acle.h`
`__pli`	Inserts a PLI instruction, if supported.	Yes	`arm_acle.h`
`__promise`	Compiler assertion that the expression always has a nonzero value. If asserts are enabled then the promise is checked at runtime by evaluating `expr` using `assert(expr)`.	Yes. However, you must `#include <assert.h>` to use `__promise`. `__promise` has the same behavior as `assert()` unless at least one of `NDEBUG` or `__DO_NOT_LINK_PROMISE_WITH_ASSERT` is defined.	`assert.h`
`__qadd`	Inserts a saturating add instruction, if supported.	Yes	`arm_acle.h`
`__qdbl`	Inserts instructions equivalent to `qadd(val,val)`, if supported.	Yes	`arm_acle.h`
`__qsub`	Inserts a saturating subtract, or equivalent routine, if supported.	Yes	`arm_acle.h`
`__rbit`	Inserts a bit reverse instruction.	Yes	`arm_acle.h`
`__rev`	Insert a `REV`, or endian swap instruction.	Yes	`arm_acle.h`
`__return_address`	Returns value of `LR` when returning from current function, without inhibiting optimizations like inlining or tailcalling.	No. Arm recommends using inline assembly instructions.	-
`__ror`	Insert an `ROR` instruction.	Yes	`arm_acle.h`
`__schedule_barrier`	Create a sequence point without effecting memory or inserting `NOP` instructions. Functions with side effects cannot move past the new sequence point.	Yes	`arm_compat.h`
`__semihost`	Inserts an `SVC` or `BKPT` instruction.	Yes	`arm_compat.h`
`__sev`	Insert a `SEV` instruction. Error if the `SEV` instruction is not supported.	Yes	`arm_acle.h`
`__sqrt`	Inserts a `VSQRT` instruction on targets with a VFP coprocessor.	No	-
`__sqrtf`	single precision version of `__sqrt`.	No	-
`__ssat`	Inserts an `SSAT` instruction. Error if the `SSAT` instruction is not supported.	Yes	`arm_acle.h`
`__strex`	Inserts an appropriately sized Store Exclusive instruction.	No. This intrinsic is deprecated in ACLE 2.0.	-
`__strexd`	Inserts a doubleword Store Exclusive instruction.	No. This intrinsic is deprecated in ACLE 2.0.	-
`__strt`	Insert an appropriately sized `STRT` instruction.	No	-
`__swp`	Inserts an appropriately sized `SWP` instruction.	Yes. However, the `SWP` instruction is deprecated, and Arm does not recommend the use of `__swp`.	`arm_acle.h`
`__usat`	Inserts a `USAT` instruction. Error if the `USAT` instruction is not supported.	Yes	`arm_acle.h`
`__wfe`	Inserts a `WFE` instruction. Error if the `WFE` instruction is not supported.	Yes	`arm_acle.h`
`__wfi`	Inserts a `WFI` instruction. Error if the `WFI` instruction is not supported.	Yes	`arm_acle.h`
`__yield`	Inserts a `YIELD` instruction. Error if the `YIELD` instruction is not supported.	Yes	`arm_acle.h`
`ARMv6 SIMD intrinsics`	Inserts an Armv6 SIMD instruction.	No	-
`ETSI intrinsics`	35 intrinsic functions and 2 global variable flags specified in ETSI G729 used for speech encoding. These are provided in the Arm headers in dspfns.h.	No	-
`C55x intrinsics`	Emulation of selected TI C55x compiler intrinsics.	No	-
`__vfp_status`	Reads the FPSCR.	Yes	`arm_compat.h`
`FMA intrinsics`	Intrinsics for fused-multiply-add on the Cortex^®-M4 or Cortex‑A5 processor in c99 mode.	No	-

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Language extension compatibility: intrinsics

4.4 Language extension compatibility: intrinsics

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