libatomic: Cleanup AArch64 ifunc selection
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| linaro-tcwg-bot/tcwg_gcc_build--master-arm |
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| linaro-tcwg-bot/tcwg_gcc_build--master-aarch64 |
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| linaro-tcwg-bot/tcwg_gcc_check--master-arm |
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| linaro-tcwg-bot/tcwg_gcc_check--master-aarch64 |
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Commit Message
Simplify and cleanup ifunc selection logic. Since LRCPC3 does
not imply LSE2, has_rcpc3() should also check LSE2 is enabled.
Passes regress and bootstrap, OK for commit?
libatomic:
* config/linux/aarch64/host-config.h (has_lse2): Cleanup.
(has_lse128): Likewise.
(has_rcpc3): Add early check for LSE2.
---
@@ -91,69 +91,62 @@ has_lse2 (unsigned long hwcap, const __ifunc_arg_t *features)
/* Check for LSE2. */
if (hwcap & HWCAP_USCAT)
return true;
- /* No point checking further for atomic 128-bit load/store if LSE
- prerequisite not met. */
- if (!(hwcap & HWCAP_ATOMICS))
- return false;
- if (!(hwcap & HWCAP_CPUID))
- return false;
- unsigned long midr;
- asm volatile ("mrs %0, midr_el1" : "=r" (midr));
+ /* If LSE and CPUID are supported, check MIDR. */
+ if (hwcap & HWCAP_CPUID && hwcap & HWCAP_ATOMICS)
+ {
+ unsigned long midr;
+ asm volatile ("mrs %0, midr_el1" : "=r" (midr));
- /* Neoverse N1 supports atomic 128-bit load/store. */
- if (MIDR_IMPLEMENTOR (midr) == 'A' && MIDR_PARTNUM (midr) == 0xd0c)
- return true;
+ /* Neoverse N1 supports atomic 128-bit load/store. */
+ return MIDR_IMPLEMENTOR (midr) == 'A' && MIDR_PARTNUM (midr) == 0xd0c;
+ }
return false;
}
-/* LSE128 atomic support encoded in ID_AA64ISAR0_EL1.Atomic,
- bits[23:20]. The expected value is 0b0011. Check that. */
+/* LSE128 atomic support encoded in ID_AA64ISAR0_EL1.Atomic, bits[23:20].
+ The minimum value for LSE128 is 0b0011. */
#define AT_FEAT_FIELD(isar0) (((isar0) >> 20) & 15)
static inline bool
has_lse128 (unsigned long hwcap, const __ifunc_arg_t *features)
{
- if (hwcap & _IFUNC_ARG_HWCAP
- && features->_hwcap2 & HWCAP2_LSE128)
- return true;
- /* A 0 HWCAP2_LSE128 bit may be just as much a sign of missing HWCAP2 bit
- support in older kernels as it is of CPU feature absence. Try fallback
- method to guarantee LSE128 is not implemented.
-
- In the absence of HWCAP_CPUID, we are unable to check for LSE128.
- If feature check available, check LSE2 prerequisite before proceeding. */
- if (!(hwcap & HWCAP_CPUID) || !(hwcap & HWCAP_USCAT))
- return false;
-
- unsigned long isar0;
- asm volatile ("mrs %0, ID_AA64ISAR0_EL1" : "=r" (isar0));
- if (AT_FEAT_FIELD (isar0) >= 3)
+ if (hwcap & _IFUNC_ARG_HWCAP && features->_hwcap2 & HWCAP2_LSE128)
return true;
+
+ /* If LSE2 and CPUID are supported, check for LSE128. */
+ if (hwcap & HWCAP_CPUID && hwcap & HWCAP_USCAT)
+ {
+ unsigned long isar0;
+ asm volatile ("mrs %0, ID_AA64ISAR0_EL1" : "=r" (isar0));
+ return AT_FEAT_FIELD (isar0) >= 3;
+ }
+
return false;
}
-/* LRCPC atomic support encoded in ID_AA64ISAR1_EL1.Atomic, bits[23:20]. The
- expected value is 0b0011. Check that. */
+/* LRCPC atomic support encoded in ID_AA64ISAR1_EL1.Atomic, bits[23:20].
+ The minimum value for LRCPC3 is 0b0011. */
static inline bool
has_rcpc3 (unsigned long hwcap, const __ifunc_arg_t *features)
{
- if (hwcap & _IFUNC_ARG_HWCAP
- && features->_hwcap2 & HWCAP2_LRCPC3)
- return true;
- /* Try fallback feature check method to guarantee LRCPC3 is not implemented.
-
- In the absence of HWCAP_CPUID, we are unable to check for RCPC3, return.
- If feature check available, check LSE2 prerequisite before proceeding. */
- if (!(hwcap & HWCAP_CPUID) || !(hwcap & HWCAP_USCAT))
+ /* LSE2 is a prerequisite for atomic LDIAPP/STILP. */
+ if (!(hwcap & HWCAP_USCAT))
return false;
- unsigned long isar1;
- asm volatile ("mrs %0, ID_AA64ISAR1_EL1" : "=r" (isar1));
- if (AT_FEAT_FIELD (isar1) >= 3)
+
+ if (hwcap & _IFUNC_ARG_HWCAP && features->_hwcap2 & HWCAP2_LRCPC3)
return true;
+
+ if (hwcap & HWCAP_CPUID)
+ {
+ unsigned long isar1;
+ asm volatile ("mrs %0, ID_AA64ISAR1_EL1" : "=r" (isar1));
+ return AT_FEAT_FIELD (isar1) >= 3;
+ }
+
return false;
}