[llvm] [TargetParser][AArch64] Believe runtime feature detection (PR #95694)

[via llvm-commits]

https://github.com/workingjubilee updated https://github.com/llvm/llvm-project/pull/95694

>From 56265e59e6729990ec3984c897999b5417b70ceb Mon Sep 17 00:00:00 2001
From: Jubilee Young <workingjubilee at gmail.com>
Date: Sun, 16 Jun 2024 01:59:59 -0700
Subject: [PATCH] [TargetParser][AArch64] Believe runtime feature detection

---
 llvm/lib/TargetParser/Host.cpp | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/llvm/lib/TargetParser/Host.cpp b/llvm/lib/TargetParser/Host.cpp
index 2ea56746aff24..0cb0419746459 100644
--- a/llvm/lib/TargetParser/Host.cpp
+++ b/llvm/lib/TargetParser/Host.cpp
@@ -1967,21 +1967,23 @@ bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
   }
 
 #if defined(__aarch64__)
-  // If we have all crypto bits we can add the feature
-  if (crypto == (CAP_AES | CAP_PMULL | CAP_SHA1 | CAP_SHA2))
-    Features["crypto"] = true;
+  // LLVM has decided some AArch64 CPUs have all the instructions they _may_
+  // have, as opposed to all the instructions they _must_ have, so allow runtime
+  // information to correct us on that.
+  Features["crypto"] = (crypto == (CAP_AES | CAP_PMULL | CAP_SHA1 | CAP_SHA2));
 #endif
 
   return true;
 }
 #elif defined(_WIN32) && (defined(__aarch64__) || defined(_M_ARM64))
 bool sys::getHostCPUFeatures(StringMap<bool> &Features) {
-  if (IsProcessorFeaturePresent(PF_ARM_NEON_INSTRUCTIONS_AVAILABLE))
-    Features["neon"] = true;
-  if (IsProcessorFeaturePresent(PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE))
-    Features["crc"] = true;
-  if (IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE))
-    Features["crypto"] = true;
+  // If we're asking the OS at runtime, believe what the OS says
+  Features["neon"] =
+      IsProcessorFeaturePresent(PF_ARM_NEON_INSTRUCTIONS_AVAILABLE);
+  Features["crc"] =
+      IsProcessorFeaturePresent(PF_ARM_V8_CRC32_INSTRUCTIONS_AVAILABLE);
+  Features["crypto"] =
+      IsProcessorFeaturePresent(PF_ARM_V8_CRYPTO_INSTRUCTIONS_AVAILABLE);
 
   return true;
 }