[RemoveDIs] Print IR with debug records by default (#91724)

This patch makes the final major change of the RemoveDIs project, changing the
default IR output from debug intrinsics to debug records.

[RemoveDIs] Print IR with debug records by default (#91724)

This patch makes the final major change of the RemoveDIs project, changing the
default IR output from debug intrinsics to debug records. This is expected to
break a large number of tests: every single one that tests for uses or
declarations of debug intrinsics and does not explicitly disable writing
records.

If this patch has broken your downstream tests (or upstream tests on a
configuration I wasn't able to run):
1. If you need to immediately unblock a build, pass
`--write-experimental-debuginfo=false` to LLVM's option processing for all
failing tests (remember to use `-mllvm` for clang/flang to forward arguments to
LLVM).
2. For most test failures, the changes are trivial and mechanical, enough that
they can be done by script; see the migration guide for a guide on how to do
this: https://llvm.org/docs/RemoveDIsDebugInfo.html#test-updates
3. If any tests fail for reasons other than FileCheck check lines that need
updating, such as assertion failures, that is most likely a real bug with this
patch and should be reported as such.

For more information, see the recent PSA:
https://discourse.llvm.org/t/psa-ir-output-changing-from-debug-intrinsics-to-debug-records/79578

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[DebugInfo][RemoveDIs] Handle DPValues at remaining dbg.value using sites (#73788)

This patch updates the last few places in LLVM using findDbgValues that
don't also collect and handle DPValue obje

[DebugInfo][RemoveDIs] Handle DPValues at remaining dbg.value using sites (#73788)

This patch updates the last few places in LLVM using findDbgValues that
don't also collect and handle DPValue objects. This largely involves
instcombine and mem2reg changes, and are largely mechanical, calling
existing utilities on collections of DPValues instead of just
DbgValuesInsts.

A variety of tests have had RemoveDIs RUN lines added to them to cover
these behaviours. We have some technical debt of the instcombine sinking
code for DPValues not being implemented yet, so I've left FIXME stubs
indicating that we intend to cover tests with RemoveDIs but haven't yet.

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[DebugInfo] Replace UndefValue with PoisonValue in setKillLocation

This helps towards the effort to remove UndefValue from LLVM.

Related to https://discourse.llvm.org/t/auto-undef-debug-uses-of-a-d

[DebugInfo] Replace UndefValue with PoisonValue in setKillLocation

This helps towards the effort to remove UndefValue from LLVM.

Related to https://discourse.llvm.org/t/auto-undef-debug-uses-of-a-deleted-value

Reviewed By: nlopes

Differential Revision: https://reviews.llvm.org/D140905

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[test][InstCombine] Update some test cases to use opaque pointers

These tests cases were converted using the script at
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

Differential Re

[test][InstCombine] Update some test cases to use opaque pointers

These tests cases were converted using the script at
https://gist.github.com/nikic/98357b71fd67756b0f064c9517b62a34

Differential Revision: https://reviews.llvm.org/D135094

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[test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC

Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://r

[test] Use -passes=instcombine instead of -instcombine in lots of tests. NFC

Another step moving away from the deprecated syntax of specifying
pass pipeline in opt.

Differential Revision: https://reviews.llvm.org/D119081

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[InstCombine] Remove dbg.values describing contents of dead allocas

When InstCombine removes an alloca, it erases the dbg.{addr,declare}
instructions which refer to the alloca. It would be better to

[InstCombine] Remove dbg.values describing contents of dead allocas

When InstCombine removes an alloca, it erases the dbg.{addr,declare}
instructions which refer to the alloca. It would be better to instead
remove all debug intrinsics which describe the contents of the dead
alloca, namely all dbg.value(<dead alloca>, ..., DW_OP_deref)'s.

This effectively undoes work performed in an InstCombine run earlier in
the pipeline by LowerDbgDeclare, which inserts DW_OP_deref dbg.values
before CallInst users of an alloca. The motivating example looks like:

```
define void @foo(i32 %0) {
%a = alloca i32 ; This alloca is erased.
store i32 %0, i32* %a
dbg.value(i32 %0, "arg0") ; This dbg.value survives.
dbg.value(i32* %a, "arg0", DW_OP_deref)
call void @trivially_inlinable_no_op(i32* %a)
ret void
}
```

If the DW_OP_deref dbg.value is not erased, it becomes dbg.value(undef)
after inlining, making "arg0" unavailable. But we already have dbg.value
descriptions of the alloca's value (from LowerDbgDeclare), so the
DW_OP_deref dbg.value cannot serve its purpose of describing an
initialization of the alloca by some callee. It invalidates other useful
dbg.values, causing large gaps in location coverage, so we should delete
it (even though doing so may cause stale dbg.values to appear, if
there's a dead store to `%a` in @trivially_inlinable_no_op).

OTOH, it wouldn't be correct to delete all dbg.value descriptions of an
alloca. Note that it's possible to describe a variable that takes on
different pointer values, e.g.:

```
void use(int *);
void t(int a, int b) {
int *local = &a; // dbg.value(i32* %a.addr, "local")
local = &b; // dbg.value(i32* undef, "local")
use(&a); // (note: %b.addr is optimized out)
local = &a; // dbg.value(i32* %a.addr, "local")
}
```

In this example, the alloca for "b" is erased, but we need to describe
the value of "local" as <unavailable> before the call to "use". This
prevents "local" from appearing to be equal to "&a" at the callsite.

rdar://66592859

Differential Revision: https://reviews.llvm.org/D85555

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