Changes to the instruction set
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1. Numerous 64 bit extensions and floating point/integer conversion ops.
2. Conditional move instructions.
New optimizations in the Alpha backend
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1. Propagation of annotations
2. SnADD SnSUB (shift and add, shift and substract)
instructions are generated whenever possible.
3. Multiplication and division by a constant now generates special code.
4. NOTB folding is implemented. This optimization combines NOTB with
other bit ops, such as ANDB, ORB, NOTB.
5. COND expressions now generate compares or conditonal moves.
Special flags in the Alpha backend
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1. mode32bit -- when this flag is set,
LOAD(32,...) will always be sign extended.
2. useSU -- when this flag is set the floating point arithmetic
will use the /SU rounding mode. Otherwise, /SUD is used.
3. multCost -- the estimated cost of integer multiplication. The
multiplication/division by a constant module uses this parameter.