Current powerpc backend generates wrong code sequence if stack pointer
has to realign if `-fstack-clash-protection` enabled. When probing
dynamic stack allocation, current `PREPARE_PROBED_ALLOCA` takes
`NegSizeReg` as input and returns
`FinalStackPtr`. `FinalStackPtr=StackPtr+ActualNegSize` is calculated
correctly, however code following `PREPARE_PROBED_ALLOCA` still uses
value of `NegSizeReg`, which does not contain `ActualNegSize` if
`MaxAlign > TargetAlign`, to calculate loop trip count and residual
number of bytes.
This patch is part of fix of
https://bugs.llvm.org/show_bug.cgi?id=46759.
Differential Revision: https://reviews.llvm.org/D84152
tryLatency compares two sched candidates. For the top zone it prefers
the one with lesser depth, but only if that depth is greater than the
total latency of the instructions we've already scheduled -- otherwise
its latency would be hidden and there would be no stall.
Unfortunately it only tests the depth of one of the candidates. This can
lead to situations where the TopDepthReduce heuristic does not kick in,
but a lower priority heuristic chooses the other candidate, whose depth
*is* greater than the already scheduled latency, which causes a stall.
The fix is to apply the heuristic if the depth of *either* candidate is
greater than the already scheduled latency.
All this also applies to the BotHeightReduce heuristic in the bottom
zone.
Differential Revision: https://reviews.llvm.org/D72392
This patch is part of supporting `-fstack-clash-protection`. Mainly do
such things compared to existing `lowerDynamicAlloc`
- Added a new pseudo instruction PPC::PREPARE_PROBED_ALLOC to get
actual frame pointer and final stack pointer.
- Synthesize a loop to probe by blocks.
- Use DYNAREAOFFSET to get MaxCallFrameSize which is calculated in
prologepilog.
Differential Revision: https://reviews.llvm.org/D81358
Kai Luo