[AArch64] Disable FEAT_RNG on Neoverse V2. #166387
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FEAT_RNG is a configurable option of the Neoverse V2 that not all SoCs implement. This patch removes FEAT_RNG from the features defined by the Neoverse V2 such that the ACLE random number generation intrinsics are not automatically enabled in cores that do not support the corresponding instructions. We also add support for parsing +rng from `/proc/cpuinfo` to minimise disruption to current Neoverse V2 users compiling with `-mcpu=native`. We test this in a new test file, `aarch64-neoverse-v2-crypto-rng.c`, which mocks a hypothetical Neoverse V2-based SoC configured with cryptographic and random number generator extensions.
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@llvm/pr-subscribers-clang @llvm/pr-subscribers-clang-driver Author: Ricardo Jesus (rj-jesus) ChangesFEAT_RNG is a configurable option of the Neoverse V2 that not all SoCs implement. This patch removes FEAT_RNG from the features defined by the Neoverse V2 such that the ACLE random number generation intrinsics are not automatically enabled for cores that do not support the respective instructions. We also add support for parsing +rng from Full diff: https://github.com/llvm/llvm-project/pull/166387.diff 6 Files Affected:
diff --git a/clang/test/Driver/Inputs/cpunative/neoverse-v2-crypto-rng b/clang/test/Driver/Inputs/cpunative/neoverse-v2-crypto-rng
new file mode 100644
index 0000000000000..e01315158057c
--- /dev/null
+++ b/clang/test/Driver/Inputs/cpunative/neoverse-v2-crypto-rng
@@ -0,0 +1,8 @@
+processor : 0
+BogoMIPS : 2000.00
+Features : fp asimd evtstrm aes pmull sha1 sha2 crc32 atomics fphp asimdhp cpuid asimdrdm jscvt fcma lrcpc dcpop sha3 sm3 sm4 asimddp sha512 sve asimdfhm dit uscat ilrcpc flagm ssbs sb paca pacg dcpodp sve2 sveaes svepmull svebitperm svesha3 svesm4 flagm2 frint svei8mm svebf16 i8mm bf16 dgh rng bti
+CPU implementer : 0x41
+CPU architecture: 8
+CPU variant : 0x0
+CPU part : 0xd4f
+CPU revision : 0
diff --git a/clang/test/Driver/print-enabled-extensions/aarch64-grace.c b/clang/test/Driver/print-enabled-extensions/aarch64-grace.c
index b66e649965489..acb641e3b2c8d 100644
--- a/clang/test/Driver/print-enabled-extensions/aarch64-grace.c
+++ b/clang/test/Driver/print-enabled-extensions/aarch64-grace.c
@@ -42,7 +42,6 @@
// CHECK-NEXT: FEAT_PMUv3 Enable Armv8.0-A PMUv3 Performance Monitors extension
// CHECK-NEXT: FEAT_RAS, FEAT_RASv1p1 Enable Armv8.0-A Reliability, Availability and Serviceability Extensions
// CHECK-NEXT: FEAT_RDM Enable Armv8.1-A Rounding Double Multiply Add/Subtract instructions
-// CHECK-NEXT: FEAT_RNG Enable Random Number generation instructions
// CHECK-NEXT: FEAT_SB Enable Armv8.5-A Speculation Barrier
// CHECK-NEXT: FEAT_SEL2 Enable Armv8.4-A Secure Exception Level 2 extension
// CHECK-NEXT: FEAT_SHA1, FEAT_SHA256 Enable SHA1 and SHA256 support
diff --git a/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2-crypto-rng.c b/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2-crypto-rng.c
new file mode 100644
index 0000000000000..a6dae9ae3de42
--- /dev/null
+++ b/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2-crypto-rng.c
@@ -0,0 +1,64 @@
+// REQUIRES: aarch64-registered-target,aarch64-host,system-linux
+// RUN: %clang --target=aarch64 --print-enabled-extensions -mcpu=neoverse-v2+rng+sve-aes+sve-sha3+sve-sm4 | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s
+// RUN: env LLVM_CPUINFO=%S/../Inputs/cpunative/neoverse-v2-crypto-rng %clang --target=aarch64 --print-enabled-extensions -mcpu=native | FileCheck --strict-whitespace --implicit-check-not=FEAT_ %s
+
+// CHECK: Extensions enabled for the given AArch64 target
+// CHECK-EMPTY:
+// CHECK-NEXT: Architecture Feature(s) Description
+// CHECK-NEXT: FEAT_AES, FEAT_PMULL Enable AES support
+// CHECK-NEXT: FEAT_AMUv1 Enable Armv8.4-A Activity Monitors extension
+// CHECK-NEXT: FEAT_AdvSIMD Enable Advanced SIMD instructions
+// CHECK-NEXT: FEAT_BF16 Enable BFloat16 Extension
+// CHECK-NEXT: FEAT_BTI Enable Branch Target Identification
+// CHECK-NEXT: FEAT_CCIDX Enable Armv8.3-A Extend of the CCSIDR number of sets
+// CHECK-NEXT: FEAT_CRC32 Enable Armv8.0-A CRC-32 checksum instructions
+// CHECK-NEXT: FEAT_CSV2_2 Enable architectural speculation restriction
+// CHECK-NEXT: FEAT_DIT Enable Armv8.4-A Data Independent Timing instructions
+// CHECK-NEXT: FEAT_DPB Enable Armv8.2-A data Cache Clean to Point of Persistence
+// CHECK-NEXT: FEAT_DPB2 Enable Armv8.5-A Cache Clean to Point of Deep Persistence
+// CHECK-NEXT: FEAT_DotProd Enable dot product support
+// CHECK-NEXT: FEAT_ETE Enable Embedded Trace Extension
+// CHECK-NEXT: FEAT_FCMA Enable Armv8.3-A Floating-point complex number support
+// CHECK-NEXT: FEAT_FHM Enable FP16 FML instructions
+// CHECK-NEXT: FEAT_FP Enable Armv8.0-A Floating Point Extensions
+// CHECK-NEXT: FEAT_FP16 Enable half-precision floating-point data processing
+// CHECK-NEXT: FEAT_FPAC Enable Armv8.3-A Pointer Authentication Faulting enhancement
+// CHECK-NEXT: FEAT_FRINTTS Enable FRInt[32|64][Z|X] instructions that round a floating-point number to an integer (in FP format) forcing it to fit into a 32- or 64-bit int
+// CHECK-NEXT: FEAT_FlagM Enable Armv8.4-A Flag Manipulation instructions
+// CHECK-NEXT: FEAT_FlagM2 Enable alternative NZCV format for floating point comparisons
+// CHECK-NEXT: FEAT_I8MM Enable Matrix Multiply Int8 Extension
+// CHECK-NEXT: FEAT_JSCVT Enable Armv8.3-A JavaScript FP conversion instructions
+// CHECK-NEXT: FEAT_LOR Enable Armv8.1-A Limited Ordering Regions extension
+// CHECK-NEXT: FEAT_LRCPC Enable support for RCPC extension
+// CHECK-NEXT: FEAT_LRCPC2 Enable Armv8.4-A RCPC instructions with Immediate Offsets
+// CHECK-NEXT: FEAT_LSE Enable Armv8.1-A Large System Extension (LSE) atomic instructions
+// CHECK-NEXT: FEAT_LSE2 Enable Armv8.4-A Large System Extension 2 (LSE2) atomicity rules
+// CHECK-NEXT: FEAT_MPAM Enable Armv8.4-A Memory system Partitioning and Monitoring extension
+// CHECK-NEXT: FEAT_MTE, FEAT_MTE2 Enable Memory Tagging Extension
+// CHECK-NEXT: FEAT_NV, FEAT_NV2 Enable Armv8.4-A Nested Virtualization Enchancement
+// CHECK-NEXT: FEAT_PAN Enable Armv8.1-A Privileged Access-Never extension
+// CHECK-NEXT: FEAT_PAN2 Enable Armv8.2-A PAN s1e1R and s1e1W Variants
+// CHECK-NEXT: FEAT_PAuth Enable Armv8.3-A Pointer Authentication extension
+// CHECK-NEXT: FEAT_PMUv3 Enable Armv8.0-A PMUv3 Performance Monitors extension
+// CHECK-NEXT: FEAT_RAS, FEAT_RASv1p1 Enable Armv8.0-A Reliability, Availability and Serviceability Extensions
+// CHECK-NEXT: FEAT_RDM Enable Armv8.1-A Rounding Double Multiply Add/Subtract instructions
+// CHECK-NEXT: FEAT_RNG Enable Random Number generation instructions
+// CHECK-NEXT: FEAT_SB Enable Armv8.5-A Speculation Barrier
+// CHECK-NEXT: FEAT_SEL2 Enable Armv8.4-A Secure Exception Level 2 extension
+// CHECK-NEXT: FEAT_SHA1, FEAT_SHA256 Enable SHA1 and SHA256 support
+// CHECK-NEXT: FEAT_SHA3, FEAT_SHA512 Enable SHA512 and SHA3 support
+// CHECK-NEXT: FEAT_SM4, FEAT_SM3 Enable SM3 and SM4 support
+// CHECK-NEXT: FEAT_SPE Enable Statistical Profiling extension
+// CHECK-NEXT: FEAT_SPECRES Enable Armv8.5-A execution and data prediction invalidation instructions
+// CHECK-NEXT: FEAT_SSBS, FEAT_SSBS2 Enable Speculative Store Bypass Safe bit
+// CHECK-NEXT: FEAT_SVE Enable Scalable Vector Extension (SVE) instructions
+// CHECK-NEXT: FEAT_SVE2 Enable Scalable Vector Extension 2 (SVE2) instructions
+// CHECK-NEXT: FEAT_SVE_AES, FEAT_SVE_PMULL128 Enable SVE AES and quadword SVE polynomial multiply instructions
+// CHECK-NEXT: FEAT_SVE_BitPerm Enable bit permutation SVE2 instructions
+// CHECK-NEXT: FEAT_SVE_SHA3 Enable SVE SHA3 instructions
+// CHECK-NEXT: FEAT_SVE_SM4 Enable SVE SM4 instructions
+// CHECK-NEXT: FEAT_TLBIOS, FEAT_TLBIRANGE Enable Armv8.4-A TLB Range and Maintenance instructions
+// CHECK-NEXT: FEAT_TRBE Enable Trace Buffer Extension
+// CHECK-NEXT: FEAT_TRF Enable Armv8.4-A Trace extension
+// CHECK-NEXT: FEAT_UAO Enable Armv8.2-A UAO PState
+// CHECK-NEXT: FEAT_VHE Enable Armv8.1-A Virtual Host extension
diff --git a/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2.c b/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2.c
index 6c2c2e3b0feb6..f80222ab36c56 100644
--- a/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2.c
+++ b/clang/test/Driver/print-enabled-extensions/aarch64-neoverse-v2.c
@@ -40,7 +40,6 @@
// CHECK-NEXT: FEAT_PMUv3 Enable Armv8.0-A PMUv3 Performance Monitors extension
// CHECK-NEXT: FEAT_RAS, FEAT_RASv1p1 Enable Armv8.0-A Reliability, Availability and Serviceability Extensions
// CHECK-NEXT: FEAT_RDM Enable Armv8.1-A Rounding Double Multiply Add/Subtract instructions
-// CHECK-NEXT: FEAT_RNG Enable Random Number generation instructions
// CHECK-NEXT: FEAT_SB Enable Armv8.5-A Speculation Barrier
// CHECK-NEXT: FEAT_SEL2 Enable Armv8.4-A Secure Exception Level 2 extension
// CHECK-NEXT: FEAT_SPE Enable Statistical Profiling extension
diff --git a/llvm/lib/Target/AArch64/AArch64Processors.td b/llvm/lib/Target/AArch64/AArch64Processors.td
index 11387bb97d29c..189f08dc2708f 100644
--- a/llvm/lib/Target/AArch64/AArch64Processors.td
+++ b/llvm/lib/Target/AArch64/AArch64Processors.td
@@ -1113,7 +1113,7 @@ def ProcessorFeatures {
list<SubtargetFeature> NeoverseV2 = [HasV9_0aOps, FeatureBF16, FeatureSPE,
FeaturePerfMon, FeatureETE, FeatureMatMulInt8,
FeatureNEON, FeatureSVEBitPerm, FeatureFP16FML,
- FeatureMTE, FeatureRandGen,
+ FeatureMTE,
FeatureCCIDX,
FeatureSVE, FeatureSVE2, FeatureSSBS, FeatureFullFP16, FeatureDotProd,
FeatureComplxNum, FeatureCRC, FeatureFPARMv8, FeatureJS, FeatureLSE,
diff --git a/llvm/lib/TargetParser/Host.cpp b/llvm/lib/TargetParser/Host.cpp
index c164762de2966..abaf55da92aef 100644
--- a/llvm/lib/TargetParser/Host.cpp
+++ b/llvm/lib/TargetParser/Host.cpp
@@ -2238,6 +2238,7 @@ StringMap<bool> sys::getHostCPUFeatures() {
.Case("fp", "fp-armv8")
.Case("crc32", "crc")
.Case("atomics", "lse")
+ .Case("rng", "rand")
.Case("sha3", "sha3")
.Case("sm4", "sm4")
.Case("sve", "sve")
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davemgreen
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This should be left on. People can use -mcpu=neoverse-v2+norng if they don't have it. Lots of features can be disabled for many different reasons. If Grace doesn't have it then maybe that should apply just to Grace, and we split the configs into two?
The mcpu=native change looks sensible. We should be doing that for all features AFAIU (and maybe getting them from hwcaps).
Hi, I assume the intent of having it on is to enable the usage of the random number generator intrinsics gated by some form of runtime detection? If so, should that not still be possible with AFAICT the availability of the rng intrinsics in CPUs that do not support them is not specified (or at least I couldn't find it), which can lead to attempts to execute illegal instructions from what looks like reasonable source code. From the ACLE:
There doesn't seem to be any other conditions under which __ARM_FEATURE_RNG is defined, which---unless I'm misunderstanding or missing something---seems to suggest the instructions should be available unconditionally alongside the intrinsics.
Yeah, I forgot to mention it earlier, the problem with going this route is that it will still misbehave with |
3 participants
FEAT_RNG is a configurable option of the Neoverse V2 that not all SoCs implement.
This patch removes FEAT_RNG from the features defined by the Neoverse V2 such that the ACLE random number generation intrinsics are not automatically enabled for cores that do not support the respective instructions.
We also add support for parsing +rng from
/proc/cpuinfoto minimise disruption to current Neoverse V2 users compiling with-mcpu=native. We test this in a new test file,aarch64-neoverse-v2-crypto-rng.c, which mocks a hypothetical Neoverse V2-based SoC configured with cryptographic and random number generator extensions.