This pass forward branches through conditions when it can show that the
conditions is either always true or false for a predecessor. This currently
only handles the most simple cases of this, but is successful at threading
across 2489 branches and 65 switch instructions in 176.gcc, which isn't bad.
llvm-svn: 21306
This can generate considerably shorter code, reducing the size of crafty
by almost 1%. Also fix the printing of mcrf. The code is currently
disabled until it gets a bit more testing, but should work as-is.
llvm-svn: 21298
Move the transform for select (a < 0) ? b : 0 into the dag from ppc isel
Enable the dag to fold and (setcc, 1) -> setcc for targets where setcc
always produces zero or one.
llvm-svn: 21291
* fold left shifts of 1, 2, 3 or 4 bits into adds
This doesn't save much now, but should get a serious workout once
multiplies by constants get converted to shift/add/sub sequences.
Hold on! :)
llvm-svn: 21282
0x00000..00FFF..FF
^ ^
^ ^
any number of
0's followed by
some number of
1's
then we use dep.z to just paste zeros over the input. For the special
cases where this is zxt1/zxt2/zxt4, we use those instructions instead,
because we're all about readability!!!
that's what it's about!! readability!
*twitch* ;D
llvm-svn: 21279
like this:
ldah $1,1($31)
lda $1,-1($1)
and $0,$1,$24
instead of this:
zap $0,252,$24
To get this back, the selector should recognize the ISD::AND case where this
happens and emit the appropriate ZAP instruction.
llvm-svn: 21270
things like this:
mov r9 = 65535;;
and r8 = r8, r9;;
To be emitted instead of:
zxt2 r8 = r8;;
To get this back, the selector for ISD::AND should recognize this case.
llvm-svn: 21269
to avoid redundant mov out3=r44 type instructions, we need to
tell the register allocator the truth about out? registers.
FIXME: unfortunately, since the list of allocatable registers is immutable,
we can't simply 'delete r127' from the allocation order, say, if 'out0' is
used. The only correct thing we can do is have a linear order of regs:
out7, out6 ... out2, out1, out0, r32, r33, r34 ... r126, r127
and slide a 'window' of 96 registers along this line, depending on how many
of the out? regs a function actually uses. The only downside of this is
that the out? registers will be allocated _first_, which makes the
resulting assembly ugly. :( Note this in the README. Hope this gets fixed
soon. :) (note the 3rd person speech there)
llvm-svn: 21252
