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This behavior was added in r130928 for both FastISel and SD, and then
disabled in r131156 for FastISel.
This re-enables it for FastISel with the corresponding fix.
This is triggered only when FastISel can't lower the arguments and falls
back to SelectionDAG for it.
FastISel contains a map of "register fixups" where at the end of the
selection phase it replaces all uses of a register with another
register that FastISel sometimes pre-assigned. Code at the end of
SelectionDAGISel::runOnMachineFunction is doing the replacement at the
very end of the function, while other pieces that come in before that
look through the MachineFunction and assume everything is done. In this
case, the real issue is that the code emitting COPY instructions for the
liveins (physreg to vreg) (EmitLiveInCopies) is checking if the vreg
assigned to the physreg is used, and if it's not, it will skip the COPY.
If a register wasn't replaced with its assigned fixup yet, the copy will
be skipped and we'll end up with uses of undefined registers.
This fix moves the replacement of registers before the emission of
copies for the live-ins.
The initial motivation for this fix is to enable tail calls for
swiftself functions, which were blocked because we couldn't prove that
the swiftself argument (which is callee-save) comes from a function
argument (live-in), because there was an extra copy (vreg to vreg).
A few tests are affected by this:
* llvm/test/CodeGen/AArch64/swifterror.ll: we used to spill x21
(callee-save) but never reload it because it's attached to the return.
We now don't even spill it anymore.
* llvm/test/CodeGen/*/swiftself.ll: we tail-call now.
* llvm/test/CodeGen/AMDGPU/mubuf-legalize-operands.ll: I believe this
test was not really testing the right thing, but it worked because the
same registers were re-used.
* llvm/test/CodeGen/ARM/cmpxchg-O0.ll: regalloc changes
* llvm/test/CodeGen/ARM/swifterror.ll: get rid of a copy
* llvm/test/CodeGen/Mips/*: get rid of spills and copies
* llvm/test/CodeGen/SystemZ/swift-return.ll: smaller stack
* llvm/test/CodeGen/X86/atomic-unordered.ll: smaller stack
* llvm/test/CodeGen/X86/swifterror.ll: same as AArch64
* llvm/test/DebugInfo/X86/dbg-declare-arg.ll: stack size changed
Differential Revision: https://reviews.llvm.org/D62361
llvm-svn: 362963
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This patch combines some cases of ARMISD::CMOV for integers that arise in comparisons of the form
a != b ? x : 0
a == b ? 0 : x
and that currently (e.g. in Thumb1) are emitted as branches.
Differential Revision: https://reviews.llvm.org/D34515
llvm-svn: 325323
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The code wasn't zero-extending correctly, so the comparison could
spuriously fail.
Adds some AArch64 tests to cover this case.
Inspired by D41791.
Differential Revision: https://reviews.llvm.org/D41798
llvm-svn: 322767
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Clean up after my misguided attempt in r304267 to "fix" CMP_SWAP
returning an uninitialized status value.
- I was always using tMOVi8 to zero the status register which cannot
encode higher register numbers and llvm would silently miscompile)
- Nobody was ever looking at that status value outside the expansion.
ARMDAGToDAGISel::SelectCMP_SWAP() the only place creating CMP_SWAP
instructions was not mapping anything to it. (The cmpxchg status value
from llvm IR is lowered to a manual comparison after the CMP_SWAP)
So this:
- Renames the register from "status" to "temp" it make it obvious that
it isn't used outside the expansion.
- Remove the zeroing status/temp register.
- Keep the live-in list improvements from r304267
Fixes http://llvm.org/PR34056
llvm-svn: 310534
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This is the equivalent of r304048 for ARM:
- Rewrite livein calculation to use the computeLiveIns() helper
function. This is slightly less efficient but easier to reason about
and doesn't unnecessarily add pristine and reserved registers[1]
- Zero the status register at the beginning of the loop to make sure it
has a defined value.
- Remove kill flags of values that need to stay alive throughout the loop.
[1] An upcoming commit of mine will tighten the MachineVerifier to catch
these.
llvm-svn: 304267
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Summary:
This patch fixes comparison of 64-bit atomic with its expected value in CMP_SWAP_64 expansion.
Currently, the low words are compared with CMP, while the high words are compared with SBC. SBC expects the carry flag to be set if CMP detects a difference. CMP might leave the carry unset for unequal arguments though if the first one is >= than the second. This might cause the comparison logic to detect false equality.
Example of the broken C++ code:
```
std::atomic<long long> at(2);
long long ll = 1;
std::atomic_compare_exchange_strong(&at, &ll, 3);
```
Even though the atomic `at` and the expected value `ll` are not equal and `atomic_compare_exchange_strong` returns `false`, `at` is changed to 3.
The patch replaces SBC with CMPEQ.
Reviewers: t.p.northover
Subscribers: aemerson, rengolin, llvm-commits, asl
Differential Revision: https://reviews.llvm.org/D27315
llvm-svn: 288433
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llvm-svn: 271340
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Physregs have no associated register class, do not attempt to modify it
in Thumb2InstrInfo::storeRegToStackSlot()/loadFromStackSlot().
llvm-svn: 271339
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transferSuccessors() would LoadCmpBB a successor of DoneBB, whereas
it should be a successor of the original MBB.
The testcase changes are caused by Thumb2SizeReduction, which
was previously confused by the broken CFG.
Follow-up to r266679.
Unfortunately, it's tricky to catch this in the verifier.
llvm-svn: 267778
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Because lowering of CMP_SWAP_64 occurs during type legalization, there can be
i64 types produced by more than just a BUILD_PAIR or similar. My initial tests
used just incoming function args.
llvm-svn: 266828
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The fast register-allocator cannot cope with inter-block dependencies without
spilling. This is fine for ldrex/strex loops coming from atomicrmw instructions
where any value produced within a block is dead by the end, but not for
cmpxchg. So we lower a cmpxchg at -O0 via a pseudo-inst that gets expanded
after regalloc.
Fortunately this is at -O0 so we don't have to care about performance. This
simplifies the various axes of expansion considerably: we assume a strong
seq_cst operation and ensure ordering via the always-present DMB instructions
rather than v8 acquire/release instructions.
Should fix the 32-bit part of PR25526.
llvm-svn: 266679
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