[PATCH v4 4/4] build/clang: add a check whether the assembler supports .skip with labels

[Roger Pau Monne <roger.pau@citrix.com>]

Or else switch off the integrated assembler. This is relevant for
older clang versions which integrated assembler don't support .skip
with labels.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Wei Liu <wei.liu2@citrix.com>
---
 xen/Rules.mk | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/Rules.mk b/xen/Rules.mk
index 322e11dba2..415b363859 100644
--- a/xen/Rules.mk
+++ b/xen/Rules.mk
@@ -72,7 +72,11 @@ AFLAGS-y                += -D__ASSEMBLY__
 
 # Older clang's built-in assembler doesn't understand .skip with labels:
 # https://bugs.llvm.org/show_bug.cgi?id=27369
-AFLAGS-$(clang)         += -no-integrated-as
+ifeq ($(clang),y)
+ifeq ($(call as-insn,$(CC) $(AFLAGS),".L0:\n.L1:\n.skip (.L1 - .L0)",y,n),n)
+        AFLAGS += -no-integrated-as
+endif
+endif
 
 ALL_OBJS := $(ALL_OBJS-y)
 
-- 
2.16.1


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