From fb05198bddcc21b97232df5f4000583d66d033b3 Mon Sep 17 00:00:00 2001
From: David Gao <davidgao@google.com>
Date: Thu, 20 Jan 2022 00:44:17 +0000
Subject: [PATCH] Port EIGEN_OPTIMIZATION_BARRIER to soft float arm

---
 Eigen/src/Core/util/Macros.h | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/Eigen/src/Core/util/Macros.h b/Eigen/src/Core/util/Macros.h
index 32bb16805..62566eec9 100644
--- a/Eigen/src/Core/util/Macros.h
+++ b/Eigen/src/Core/util/Macros.h
@@ -1002,11 +1002,17 @@ namespace Eigen {
       // General, Altivec, VSX.
       #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+r,v,wa" (X));
     #elif EIGEN_ARCH_ARM_OR_ARM64
-      // General, NEON.
-      // Clang doesn't like "r",
-      //    error: non-trivial scalar-to-vector conversion, possible invalid
-      //           constraint for vector typ
-      #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+g,w" (X));
+      #ifdef __ARM_FP
+        // General, VFP or NEON.
+        // Clang doesn't like "r",
+        //    error: non-trivial scalar-to-vector conversion, possible invalid
+        //           constraint for vector typ
+        #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+g,w" (X));
+      #else
+        // Arm without VFP or NEON.
+        // "w" constraint will not compile.
+        #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+g" (X));
+      #endif
     #elif EIGEN_ARCH_i386_OR_x86_64
       // General, SSE.
       #define EIGEN_OPTIMIZATION_BARRIER(X)  __asm__  ("" : "+g,x" (X));