Free the second half of double register #46939
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This was referenced Jan 16, 2021
BruceForstall
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kunalspathak
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This reverts commit 0f86c45.
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As pointed out in my analysis in #46085 (comment), after #45135, we added a
DEBUGonly validation that checks if aRegRecorddoesn't have an assigned interval, it should be free and its entry should be present inm_AvailableRegsmask. However, for ARM, that invariant was not maintained.In Arm, a pair of registers are used to store value of
TYP_DOUBLE. However, if a register pair was previously assigned to an interval that hasTYP_DOUBLEvalue and we are currently trying to assign a register to an interval that hasTYP_FLOATvalue, we unassign both registers and re-assign one of the register of the pair to the current interval. However, we were not marking the other half register as free. This is done inliveRegsthat tracks the live variables. The fix was that whenever we see this happening, remove the other half register from theliveRegsmask, so it is considered as free.JitStressregs is green. The failures in JitStress2-JitStressRegs are unrelated and are because of the following issues:
Fixes: #46085