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Add a note that we should match rlwnm better
llvm-svn: 30508
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3057944738
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ee42b9ae24
@ -6,6 +6,40 @@ TODO:
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===-------------------------------------------------------------------------===
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We only produce the rlwnm instruction for rotate instructions. We should
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at least match stuff like:
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unsigned rot_and(unsigned X, int Y) {
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unsigned T = (X << Y) | (X >> (32-Y));
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T &= 127;
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return T;
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}
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_foo3:
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rlwnm r2, r3, r4, 0, 31
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rlwinm r3, r2, 0, 25, 31
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blr
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... which is the basic pattern that should be written in the instr. It may
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also be useful for stuff like:
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long long foo2(long long X, int C) {
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return X << (C&~32);
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}
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which currently produces:
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_foo2:
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rlwinm r2, r5, 0, 27, 25
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subfic r5, r2, 32
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slw r3, r3, r2
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srw r5, r4, r5
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or r3, r3, r5
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slw r4, r4, r2
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blr
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===-------------------------------------------------------------------------===
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Support 'update' load/store instructions. These are cracked on the G5, but are
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still a codesize win.
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