• Austin Clements's avatar
    [dev.power64] 9g: fix under-zeroing in clearfat · 6e860036
    Austin Clements authored
    All three cases of clearfat were wrong on power64x.
    
    The cases that handle 1032 bytes and up and 32 bytes and up
    both use MOVDU (one directly generated in a loop and the other
    via duffzero), which leaves the pointer register pointing at
    the *last written* address.  The generated code was not
    accounting for this, so the byte fill loop was re-zeroing the
    last zeroed dword, rather than the bytes following the last
    zeroed dword.  Fix this by simply adding an additional 8 byte
    offset to the byte zeroing loop.
    
    The case that handled under 32 bytes was also wrong.  It
    didn't update the pointer register at all, so the byte zeroing
    loop was simply re-zeroing the beginning of region.  Again,
    the fix is to add an offset to the byte zeroing loop to
    account for this.
    
    LGTM=dave, bradfitz
    R=rsc, dave, bradfitz
    CC=golang-codereviews
    https://golang.org/cl/168870043
    6e860036
ggen.c 21.8 KB