The function prolog logic is now separated in its own basic block. The
first "real" block with user code starts at offset 0.
Having the function prolog as a hidden part of the first block caused
some inconsistencies in block generation and would create empty blocks.
This happened for example when a back edge of a loop would target offset
0 in code where a loop condition is the very first set of instructions
that are run. This is because the target block offset didn't exist due
to it being part of the hidden prolog block.
Validation for the basic blocks was also added. This checks for three
things at the moment:
1. That return and throw blocks don't have jump targets.
2. That the basic blocks graph is connected.
3. That jump targets are the first offset of a block.
Test tst_QmlCppCodegen::basicBlocksWithBackJump_infinite() is expected
to fail because it contains an infinite loop and the basic blocks that
are generated for it are inconsistent due to dead-code elimination
happening earlier in compilation.
Debug outputs for dumping basic blocks were also adapted to reflect
these changes.
Change-Id: I513f73856412d488d443c2b47a052b0023d45496
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Olivier De Cannière