[FIRRTL] FoldUnusedBits: Cast compressed data back to signed integer #7913
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youngar
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seldridge
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| // the memory. | ||
| if (type.isSigned()) | ||
| catOfSlices = | ||
| rewriter.createOrFold<AsSIntPrimOp>(writeOp.getLoc(), catOfSlices); |
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This patch doesn't seem to fix chipsalliance/chisel#4536, please see this comment |
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The FoldUnusedBits folder will, when it sees a memory with obviously unused bits (all readers are bitselect ops), will compress that memory to a smaller integer. The data written to the memory has to be compressed to just the relevant bits, which is done using a sequence of bit-select and bit-concat ops on the data. The result of these ops is unsigned. If the memory itself stores a signed integer, then we need to cast this data back to a signed value.