From 590bb3e8e63af0fb46eadf510761bd00e264c018 Mon Sep 17 00:00:00 2001
From: Eli Friedman <efriedma@qti.qualcomm.com>
Date: Mon, 24 Nov 2025 14:08:50 -0800
Subject: [PATCH] [AArch64] Improve host feature detection. (#160410)

SVE depends on a combination of host support and operating system
support. Sometimes those don't line up with detected host CPU name; make
sure SVE is disabled when it isn't available. Implement this for both
Windows and Linux. (We don't have a codepath for other operating
systems. If someone wants to implement this, it should be possible to
adapt fmv code from compiler-rt.)

While I'm here, also add support for detecting other Windows CPU
features.

For Windows, declare constants ourselves so the code builds on older
SDKs; we also do this in compiler-rt.
---
 llvm/lib/TargetParser/Host.cpp | 65 ++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/TargetParser/Host.cpp b/llvm/lib/TargetParser/Host.cpp
index 3f9f69549f2d..cb793d60a286 100644
--- a/llvm/lib/TargetParser/Host.cpp
+++ b/llvm/lib/TargetParser/Host.cpp
@@ -2277,20 +2277,81 @@ StringMap<bool> sys::getHostCPUFeatures() {
   uint32_t Sha2 = CAP_SHA1 | CAP_SHA2;
   Features["aes"] = (crypto & Aes) == Aes;
   Features["sha2"] = (crypto & Sha2) == Sha2;
+
+  // Even if an underlying core supports SVE, it might not be available if
+  // it's disabled by the OS, or some other layer. Disable SVE if we don't
+  // detect support at runtime.
+  if (!Features.contains("sve"))
+    Features["sve"] = false;
 #endif
 
   return Features;
 }
 #elif defined(_WIN32) && (defined(__aarch64__) || defined(_M_ARM64) ||         \
                           defined(__arm64ec__) || defined(_M_ARM64EC))
+#ifndef PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE 43
+#endif
+#ifndef PF_ARM_V83_JSCVT_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_V83_JSCVT_INSTRUCTIONS_AVAILABLE 44
+#endif
+#ifndef PF_ARM_V83_LRCPC_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_V83_LRCPC_INSTRUCTIONS_AVAILABLE 45
+#endif
+#ifndef PF_ARM_SVE_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_INSTRUCTIONS_AVAILABLE 46
+#endif
+#ifndef PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE 47
+#endif
+#ifndef PF_ARM_SVE_PMULL128_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_PMULL128_INSTRUCTIONS_AVAILABLE 50
+#endif
+#ifndef PF_ARM_SVE_SHA3_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_SHA3_INSTRUCTIONS_AVAILABLE 55
+#endif
+#ifndef PF_ARM_SVE_SM4_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_SM4_INSTRUCTIONS_AVAILABLE 56
+#endif
+#ifndef PF_ARM_SVE_I8MM_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_I8MM_INSTRUCTIONS_AVAILABLE 57
+#endif
+#ifndef PF_ARM_SVE_F32MM_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_F32MM_INSTRUCTIONS_AVAILABLE 58
+#endif
+#ifndef PF_ARM_SVE_F64MM_INSTRUCTIONS_AVAILABLE
+#define PF_ARM_SVE_F64MM_INSTRUCTIONS_AVAILABLE 59
+#endif
 StringMap<bool> sys::getHostCPUFeatures() {
   StringMap<bool> Features;
 
   // 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["lse"] =
+      IsProcessorFeaturePresent(PF_ARM_V81_ATOMIC_INSTRUCTIONS_AVAILABLE);
+  Features["dotprod"] =
+      IsProcessorFeaturePresent(PF_ARM_V82_DP_INSTRUCTIONS_AVAILABLE);
+  Features["jsconv"] =
+      IsProcessorFeaturePresent(PF_ARM_V83_JSCVT_INSTRUCTIONS_AVAILABLE);
+  Features["rcpc"] =
+      IsProcessorFeaturePresent(PF_ARM_V83_LRCPC_INSTRUCTIONS_AVAILABLE);
+  Features["sve"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_INSTRUCTIONS_AVAILABLE);
+  Features["sve2"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE2_INSTRUCTIONS_AVAILABLE);
+  Features["sve-aes"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_PMULL128_INSTRUCTIONS_AVAILABLE);
+  Features["sve-sha3"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_SHA3_INSTRUCTIONS_AVAILABLE);
+  Features["sve-sm4"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_SM4_INSTRUCTIONS_AVAILABLE);
+  Features["f32mm"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_F32MM_INSTRUCTIONS_AVAILABLE);
+  Features["f64mm"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_F64MM_INSTRUCTIONS_AVAILABLE);
+  Features["i8mm"] =
+      IsProcessorFeaturePresent(PF_ARM_SVE_I8MM_INSTRUCTIONS_AVAILABLE);
 
   // Avoid inferring "crypto" means more than the traditional AES + SHA2
   bool TradCrypto =