Message ID | 5948DAC20200007800164514@prv-mh.provo.novell.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
On 20/06/17 07:20, Jan Beulich wrote: > First of all there's no point considering the "shift == width" case, > when immediately before that check we mask "shift" by "width - 1". And > then truncate_word() use can be reduced too: dst.val, as obtained by > generic operand fetching code, is already suitably truncated, and its > use can also be made symmetric in the main conditional expression (on > only left shift results). Finally masking the result of a right shift > is not necessary when the left hand operand doesn't have more than > "width" significant bits. > > Signed-off-by: Jan Beulich <jbeulich@suse.com> Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
--- a/xen/arch/x86/x86_emulate/x86_emulate.c +++ b/xen/arch/x86/x86_emulate/x86_emulate.c @@ -6414,16 +6414,14 @@ x86_emulate( } if ( (shift &= width - 1) == 0 ) break; - dst.orig_val = truncate_word(dst.val, dst.bytes); - dst.val = ((shift == width) ? src.val : - (b & 8) ? - /* shrd */ - ((dst.orig_val >> shift) | - truncate_word(src.val << (width - shift), dst.bytes)) : - /* shld */ - ((dst.orig_val << shift) | - ((src.val >> (width - shift)) & ((1ull << shift) - 1)))); - dst.val = truncate_word(dst.val, dst.bytes); + dst.orig_val = dst.val; + dst.val = (b & 8) ? + /* shrd */ + ((dst.orig_val >> shift) | + truncate_word(src.val << (width - shift), dst.bytes)) : + /* shld */ + (truncate_word(dst.orig_val << shift, dst.bytes) | + (src.val >> (width - shift))); _regs.eflags &= ~(X86_EFLAGS_OF | X86_EFLAGS_SF | X86_EFLAGS_ZF | X86_EFLAGS_PF | X86_EFLAGS_CF); if ( (dst.val >> ((b & 8) ? (shift - 1) : (width - shift))) & 1 )