search for: s_cbranch_execnz

...the fact that undef values are a special case since they don't have an associated VNInfo/Segment unless the value is used across blocks. For example, in this case, %0 has 2 subregisters sub0 and sub1: bb.0: undef %0.sub1:vreg_64 = COPY killed $vgpr0 bb.1: %0:vreg_64 = COPY %0 S_CBRANCH_EXECNZ %bb.1, implicit $exec bb.2: undef %0.sub1:vreg_64 = nofpexcept V_CEIL_F32_e32 killed %0.sub1, implicit $mode, implicit $exec S_BRANCH %bb.1 sub0 has no defined values anywhere in this function. The value only exists due to this identity copy in %bb.1, which is removed. When the copy is...