https://alive2.llvm.org/ce/z/oShzr3
This was noted as a missing fold in D134876 (with additional
examples based on issue #58046).
I'm assuming that fmul with a zero operand is rare enough
that the use of ValueTracking will not noticeably increase
compile-time.
This adjusts a PowerPC codegen test that was added with D88388
because it would get folded away and no longer provide coverage
for the bug fix.
This patch fixes the following two bugs in `PPCInstrInfo::isSignOrZeroExtended` helper, which is used from sign-/zero-extension elimination in PPCMIPeephole pass.
- Registers defined by load with update (e.g. LBZU) were identified as already sign or zero-extended. But it is true only for the first def (loaded value) and not for the second def (i.e. updated pointer).
- Registers defined by ORIS/XORIS were identified as already sign-extended. But, it is not true for sign extension depending on the immediate (while it is ok for zero extension).
To handle the first case, the parameter for the helpers is changed from `MachineInstr` to a register number to distinguish first and second defs. Also, this patch moves the initialization of PPCMIPeepholePass to allow mir test case.
Reviewed By: nemanjai
Differential Revision: https://reviews.llvm.org/D40554
