QBE as an easy-to-embed library
https://c9x.me/git/qbe.git
3a3c88532c
I think I should check for Top when rewriting. Because for sure, we don't want to replace some temporary by Top, first, I can't represent it, and second, it'd mean that it is a temporary used undefined. The example that triggered the assertion was like that: @b0 jnz 1, @b1, @b3 @b1 %x =w phi @b0 10, @b2 %x1 jnz %x, @b2, @b3 @b2 %x1 =w sub %x, 1 jmp @b1 @b3 %x2 =w phi @b1 %x, @b0 42 So SCCP optimistically assumes %x is 10 when it goes through @b1, then at the branch, @b1->@b3 is left for dead. After that, @b2 is processed and the flow worklist is empty. Now uses are processed, %x2 will get processed regardless if its block is dead or not (it is at that time), then all the back-edges are dead so the phi is set to the lattice merge of tops only. BOOM! This leads to the question, should phis of dead blocks be processed? I'll check that later. |
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| doc | ||
| minic | ||
| test | ||
| tools | ||
| .gitignore | ||
| .tag | ||
| all.h | ||
| copy.c | ||
| emit.c | ||
| fold.c | ||
| isel.c | ||
| LICENSE | ||
| live.c | ||
| main.c | ||
| Makefile | ||
| mem.c | ||
| parse.c | ||
| README | ||
| rega.c | ||
| spill.c | ||
| ssa.c | ||
| sysv.c | ||
| util.c | ||
QBE - Backend Compiler http://c9x.me/compile/ doc/ Documentation. minic/ An example C frontend for QBE. tools/ Miscellaneous tools (testing). test/ Unit tests. The LICENSE file applies to all files distributed.