On Mon, Feb 20, 2012 at 7:57 PM, Richard Henderson <r...@redhat.com> wrote:
>>>> tempRIP = RIP + SignExtend (IMM), >>>> >>>> where RIP is instruction following XBEGIN instruction. >>> >>> So? .+N is generic assembler syntax, not specifying IMM=6. >>> With "xbegin .+6" the assembler will of course encode IMM=0, >>> because it knows that the xbegin insn is 6 bytes. >> >> Is the "fallback code" the insn just after the xbegin insn? > > Yes. > > If you write everything in pure assembly (or if the compiler gets > really smart) then you can use the branch-like semantics and > arrange for the fallback code to be completely out of line. > > Otherwise we ignore the branch-like feature and rely entirely on > the data characteristics of the insn, in that %rax is modified. > Thus the initial set of -1 and subsequent compare vs the same. I see the logic now, somehow I have assumed the "really smart" way ;) Other than that, testing of new headers should be added to gcc.target/i386/sse-[12,13,14].c and g++.dg/other/i386-[2,3].c. Thanks, Uros.
