GIMPLE lowering pass. Converts High GIMPLE into Low GIMPLE.
Copyright (C) 2003-2024 Free Software Foundation, Inc.
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The differences between High GIMPLE and Low GIMPLE are the
following:
1- Lexical scopes are removed (i.e., GIMPLE_BIND disappears).
2- GIMPLE_TRY and GIMPLE_CATCH are converted to abnormal control
flow and exception regions are built as an on-the-side region
hierarchy (See tree-eh.cc:lower_eh_constructs).
3- Multiple identical return statements are grouped into a single
return and gotos to the unique return site.
Match a return statement with a label. During lowering, we identify
identical return statements and replace duplicates with a jump to
the corresponding label.