File 62d807c1-x86-suppress-MMX.patch of Package xen.27273

# Commit 6fe2e39a0243bddba60f83b77b972a5922d25eb8
# Date 2022-07-20 15:48:49 +0200
# Author Jan Beulich <jbeulich@suse.com>
# Committer Jan Beulich <jbeulich@suse.com>
x86: also suppress use of MMX insns

Passing -mno-sse alone is not enough: The compiler may still find
(questionable) reasons to use MMX insns. In particular with gcc12 use
of MOVD+PUNPCKLDQ+MOVQ was observed in an apparent attempt to auto-
vectorize the storing of two adjacent zeroes, 32 bits each.

Reported-by: ChrisD <chris@dalessio.org>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

--- a/xen/arch/x86/arch.mk
+++ b/xen/arch/x86/arch.mk
@@ -36,9 +36,9 @@ $(call as-option-add,CFLAGS,CC,\
 
 CFLAGS += -mno-red-zone -fpic
 
-# Xen doesn't use SSE interally.  If the compiler supports it, also skip the
-# SSE setup for variadic function calls.
-CFLAGS += -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
+# Xen doesn't use MMX or SSE interally.  If the compiler supports it, also skip
+# the SSE setup for variadic function calls.
+CFLAGS += -mno-mmx -mno-sse $(call cc-option,$(CC),-mskip-rax-setup)
 
 # Compile with thunk-extern, indirect-branch-register if avaiable.
 CFLAGS-$(CONFIG_INDIRECT_THUNK) += -mindirect-branch=thunk-extern