We normally select these when the root node is a sext_inreg, but
SimplifyDemandedBits can sometimes bypass the sext_inreg for some
users. This can create situation where sext_inreg+add/sub/mul/shl
is selected to a W instruction, and then the add/sub/mul/shl is
separately selected to a non-W instruction with the same inputs.
This patch tries to detect when it would still be ok to use a W
instruction without the sext_inreg by checking the direct users.
This can allow the W instruction to CSE with one created for a
sext_inreg+add/sub/mul/shl. To minimize complexity and cost of
checking, we make no attempt to determine if the CSE will happen
and just always use a W instruction when we can.
Differential Revision: https://reviews.llvm.org/D107658
Currently isReallyTriviallyReMaterializableGeneric() implementation
prevents rematerialization on any virtual register use on the grounds
that is not a trivial rematerialization and that we do not want to
extend liveranges.
It appears that LRE logic does not attempt to extend a liverange of
a source register for rematerialization so that is not an issue.
That is checked in the LiveRangeEdit::allUsesAvailableAt().
The only non-trivial aspect of it is accounting for tied-defs which
normally represent a read-modify-write operation and not rematerializable.
The test for a tied-def situation already exists in the
/CodeGen/AMDGPU/remat-vop.mir,
test_no_remat_v_cvt_f32_i32_sdwa_dst_unused_preserve.
The change has affected ARM/Thumb, Mips, RISCV, and x86. For the targets
where I more or less understand the asm it seems to reduce spilling
(as expected) or be neutral. However, it needs a review by all targets'
specialists.
Differential Revision: https://reviews.llvm.org/D106408
I thought this might help with another optimization I was
thinking about, but I don't think it will. So it just wastes
compile time calling computeKnownBits for no benefit.
This reverts commit 81b2f95971.
Regenerated using:
./llvm/utils/update_llc_test_checks.py -u llvm/test/CodeGen/RISCV/*.ll
This has added comments to spill-related instructions and added @plt to
some symbols.
Differential Revision: https://reviews.llvm.org/D92841
Added some tests testing urem and srem operations with a constant divisor.
Patch by TG908 (Tim Gymnich)
Differential Revision: https://reviews.llvm.org/D68421
llvm-svn: 373830
Craig Topper