From: Zoltan Varga <vargaz@gmail.com>
Date: Thu, 24 Feb 2011 12:55:13 +0000 (+0100)
Subject: Only use memory barriers on arm when running on armv6 or later.
X-Git-Url: http://wien.tomnetworks.com/gitweb/?a=commitdiff_plain;h=731db97325c15356c2c888d47207e73bc36c05f1;p=mono.git

Only use memory barriers on arm when running on armv6 or later.
---

diff --git a/configure.in b/configure.in
index 572c37bacc7..c14339f267d 100644
--- a/configure.in
+++ b/configure.in
@@ -2539,6 +2539,16 @@ if test ${TARGET} = ARM && test x$cross_compiling = xno && test x$enable_mcs_bui
 	AC_MSG_RESULT($fpu)
 	CPPFLAGS="$CPPFLAGS -DARM_FPU_$fpu=1"
 	unset fpu
+
+	AC_MSG_CHECKING(for ARMV6)
+	AC_TRY_RUN([
+		int main () { __asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r" (0) : "memory"); return 0; }
+			], armv6=yes, armv6=no)
+
+	AC_MSG_RESULT($armv6)
+	if test ${armv6} = yes; then
+	   AC_DEFINE(HAVE_ARMV6, 1, "Host supports ARMV6 instructions")
+	fi
 fi
 
 if test ${TARGET} = unknown; then
diff --git a/mono/mini/mini-arm.c b/mono/mini/mini-arm.c
index d210943de13..bf032adf167 100644
--- a/mono/mini/mini-arm.c
+++ b/mono/mini/mini-arm.c
@@ -37,6 +37,7 @@ static gint lmf_addr_tls_offset = -1;
 static CRITICAL_SECTION mini_arch_mutex;
 
 static int v5_supported = 0;
+static int v6_supported = 0;
 static int v7_supported = 0;
 static int thumb_supported = 0;
 /*
@@ -508,6 +509,7 @@ mono_arch_cpu_optimizazions (guint32 *exclude_mask)
 		thumb_supported = strstr (cpu_arch, "thumb") != NULL;
 		if (strncmp (cpu_arch, "armv", 4) == 0) {
 			v5_supported = cpu_arch [4] >= '5';
+			v6_supported = cpu_arch [4] >= '6';
 			v7_supported = cpu_arch [4] >= '7';
 		}
 	} else {
@@ -526,6 +528,8 @@ mono_arch_cpu_optimizazions (guint32 *exclude_mask)
 				char *ver = strstr (line, "(v");
 				if (ver && (ver [2] == '5' || ver [2] == '6' || ver [2] == '7'))
 					v5_supported = TRUE;
+				if (ver && (ver [2] == '6' || ver [2] == '7'))
+					v6_supported = TRUE;
 				if (ver && (ver [2] == '7'))
 					v7_supported = TRUE;
 				continue;
@@ -3291,8 +3295,10 @@ mono_arch_output_basic_block (MonoCompile *cfg, MonoBasicBlock *bb)
 
 		switch (ins->opcode) {
 		case OP_MEMORY_BARRIER:
-			ARM_MOV_REG_IMM8 (code, ARMREG_R0, 0);
-			ARM_MCR (code, 15, 0, ARMREG_R0, 7, 10, 5);
+			if (v6_supported) {
+				ARM_MOV_REG_IMM8 (code, ARMREG_R0, 0);
+				ARM_MCR (code, 15, 0, ARMREG_R0, 7, 10, 5);
+			}
 			break;
 		case OP_TLS_GET:
 #ifdef HAVE_AEABI_READ_TP
@@ -5875,8 +5881,13 @@ void
 mono_arch_set_target (char *mtriple)
 {
 	/* The GNU target triple format is not very well documented */
-	if (strstr (mtriple, "armv7"))
+	if (strstr (mtriple, "armv7")) {
+		v6_supported = TRUE;
 		v7_supported = TRUE;
+	}
+	if (strstr (mtriple, "armv7")) {
+		v6_supported = TRUE;
+	}
 	if (strstr (mtriple, "darwin")) {
 		v5_supported = TRUE;
 		thumb_supported = TRUE;
diff --git a/mono/utils/mono-membar.h b/mono/utils/mono-membar.h
index 1c343b0d454..0bd56dbeaa6 100644
--- a/mono/utils/mono-membar.h
+++ b/mono/utils/mono-membar.h
@@ -10,6 +10,8 @@
 #ifndef _MONO_UTILS_MONO_MEMBAR_H_
 #define _MONO_UTILS_MONO_MEMBAR_H_
 
+#include <config.h>
+
 #include <glib.h>
 
 #ifdef __x86_64__
@@ -129,7 +131,9 @@ static inline void mono_memory_write_barrier (void)
 #elif defined(__arm__)
 static inline void mono_memory_barrier (void)
 {
+#ifdef HAVE_ARMV6
 	__asm__ __volatile__ ("mcr p15, 0, %0, c7, c10, 5" : : "r" (0) : "memory");
+#endif
 }
 
 static inline void mono_memory_read_barrier (void)