Change Details

Remove spill-reload like copy chains. For example ``` r0 = COPY r1 r1 = COPY r2 r2 = COPY r3 r3 = COPY r4 <def-use r4> r4 = COPY r3 r3 = COPY r2 r2 = COPY r1 r1 = COPY r0 ``` will be folded into ``` r0 = COPY r1 r1 = COPY r4 <def-use r4> r4 = COPY r1 r1 = COPY r0 ```