Signed loads should not zero-def their destination.

[justinmichaud]

5838997

Signed loads should not zero-def their destination.
https://bugs.webkit.org/show_bug.cgi?id=271866
rdar://122959696

Reviewed by Yusuke Suzuki.

This fixes a hang in Google Meet when applying the Black Noir filter.

Suppose we have:

```
@a = Load8SignedExtendTo32(@x)

@b = Trunc(ZExt32(@a))
```

B3 reduceStrength will convert @b to @a. The Air register allocator will
see that we ZDef 64 bits in @a, but on ARM64, we actually sign-extend them.

This was caught by changing reduceStrength:

```
case Trunc:
    // Turn this: Trunc(SExt32(value)) or Trunc(ZExt32(value))
    // Into this: value
    if (m_value->child(0)->opcode() == SExt32 || m_value->child(0)->opcode() == ZExt32) {
        auto* value = m_value->child(0)->child(0);
        auto* patchpoint = m_insertionSet.insert<PatchpointValue>(
            m_index, m_value->type(), m_value->origin());

        patchpoint->effects = Effects();
        patchpoint->effects.reads = HeapRange::top();
        patchpoint->effects.exitsSideways = true;

        patchpoint->append(value);
        patchpoint->setGenerator([&] (CCallHelpers& jit, const StackmapGenerationParams& params) {
            RELEASE_ASSERT(params.size() == 2);
            RELEASE_ASSERT(params[0].isGPR());
            RELEASE_ASSERT(params[1].isGPR());
            auto dst = params[0].gpr();
            auto a = params[1].gpr();
            auto branch = jit.branchTest64(CCallHelpers::Zero, a, MacroAssembler::TrustedImm64(0xFFFFFFFF00000000));
            jit.breakpoint();
            jit.breakpoint(0);
            jit.breakpoint(1);
            jit.breakpoint(2);
            branch.link(&jit);
            jit.move(a, dst);
        });

        replaceWithNew<Value>(Identity, m_value->origin(), patchpoint);
```

* Source/JavaScriptCore/b3/air/AirOpcode.opcodes:

Canonical link: https://commits.webkit.org/276829@main

f74efe4

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	❌ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-skia
✅ 🛠 🧪 jsc	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
✅ 🛠 🧪 jsc-arm64	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 tv-sim		✅ 🧪 api-gtk
	✅ 🛠 watch		✅ 🛠 jsc-armv7
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim		✅ 🧪 jsc-armv7-tests

[webkit-early-warning-system]

EWS run on current version of this PR (hash f74efe4)

Misc	iOS, tvOS & watchOS	macOS	Linux	Windows
✅ 🧪 style	✅ 🛠 ios	✅ 🛠 mac	✅ 🛠 wpe	✅ 🛠 wincairo
	✅ 🛠 ios-sim	✅ 🛠 mac-AS-debug	✅ 🧪 wpe-wk2
✅ 🧪 webkitperl	✅ 🧪 ios-wk2	✅ 🧪 api-mac	❌ 🧪 api-wpe
	✅ 🧪 ios-wk2-wpt	✅ 🧪 mac-wk1	✅ 🛠 wpe-skia
✅ 🛠 🧪 jsc	✅ 🧪 api-ios	✅ 🧪 mac-wk2	✅ 🛠 gtk
✅ 🛠 🧪 jsc-arm64	✅ 🛠 tv	✅ 🧪 mac-AS-debug-wk2	✅ 🧪 gtk-wk2
	✅ 🛠 tv-sim		✅ 🧪 api-gtk
	✅ 🛠 watch		✅ 🛠 jsc-armv7
✅ 🛠 🧪 unsafe-merge	✅ 🛠 watch-sim		✅ 🧪 jsc-armv7-tests

[Constellation]

r=me

[webkit-ews-buildbot]

Failed api-wpe checks. Please resolve failures and re-apply safe-merge-queue label.

Rejecting #26593 from merge queue.

[webkit-ews-buildbot]

Safe-Merge-Queue: Build #16324.

[MenloDorian]

The api-wpe test failure is unrelated.

[webkit-commit-queue]

Committed 276829@main (5838997): https://commits.webkit.org/276829@main

Reviewed commits have been landed. Closing PR #26593 and removing active labels.