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Re: RFC: Should x86-64 support arbitrary calling conventions?

On 03/24/2017 01:41 AM, H.J. Lu wrote:

+# ifdef STATE_SAVE_MASK
+	movl $STATE_SAVE_MASK, %eax
+	xorl %edx, %edx
+	# Clear the XSAVE Header.
+	movq $0, (STATE_SAVE_OFFSET + 512)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 2)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 3)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 4)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 5)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 6)(%rsp)
+	movq $0, (STATE_SAVE_OFFSET + 512 + 8 * 7)(%rsp)
 # endif


You've just cleared %rdx.  Use that instead of 8*4 bytes of immediate zeros.
Given that you have to ifdef this code into place, isn't it somewhat pointless to hide xsave behind a macro in the next line? 


+	STATE_SAVE STATE_SAVE_OFFSET(%rsp)


I think it would be clearer to inline the two save instructions instead.


r~
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