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Fix win64 abi wrt AVX registers


As detailed in the comment, verified by ktietz via contacts
at Microsoft.

Sanity checked on x86_64-linux and committed.


r~


	* config/i386/i386.h (HARD_REGNO_CALL_PART_CLOBBERED): New.


diff --git a/gcc/config/i386/i386.h b/gcc/config/i386/i386.h
index a2acc71..7fd874b 100644
--- a/gcc/config/i386/i386.h
+++ b/gcc/config/i386/i386.h
@@ -1104,6 +1104,12 @@ enum target_cpu_default
    : (MODE) == QImode && (REGNO) > BX_REG && !TARGET_64BIT ? SImode 	\
    : (MODE))
 
+/* The only ABI that saves SSE registers across calls is Win64 (thus no
+   need to check the current ABI here), and with AVX enabled Win64 only
+   guarantees that the low 16 bytes are saved.  */
+#define HARD_REGNO_CALL_PART_CLOBBERED(REGNO, MODE)             \
+  (SSE_REGNO_P (REGNO) && GET_MODE_SIZE (MODE) > 16)
+
 /* Specify the registers used for certain standard purposes.
    The values of these macros are register numbers.  */
 


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