JIT: Preserve SIMD operand evaluation and ordering

[tannergooding]

Fixes #133718.

Preserve observable evaluation when SIMD folding discards an operand, including constant-NaN Min/Max. Keep operand evaluation and validation in source order through shift emulation, GetElement/WithElement, scalar-left multiplication, sequences, and value-first stores.

Use GTF_OBS_EFFECT to distinguish observable effects from unused ordinary reads. Carry binary evaluation order in the builders instead of relying on importer spills, including local-morph handling for reversed stores and unary local-store folding. Retain WASM, FMA, and decomposition spills where still required; avoid unnecessary captures for invariant single-lane results and direct int/uint division nodes. Also clone scalar Min/Max operands in source order on RISC-V.

This does not change NaN payload-selection policy or address the separate XCHG/local-value-interference problem.

Validation

• Windows x64 and ARM64 Checked JIT builds; required Windows x64 JIT formatting passes.
• All 23 focused regression cases pass with default ISA support and with AVX-512, AVX2, AVX, or hardware intrinsics disabled. The same assembly has 7 failures against the saved unfixed JIT.
• All 2,551 optimized general-intrinsics cases pass with default ISA support and again with AVX-512 disabled.
• Eleven x64 value/codegen controls pass against both JITs across four ISA configurations, with no size or instruction-count increases. The default Vector128<int>.CreateSequence array-load probe drops from 63 to 57 bytes and 16 to 14 instructions; direct integer-division and ordinary-store controls are unchanged. Seven pure Min/Max, Number, and finite controls have identical disassembly. These are codegen measurements, not throughput benchmarks.

ARM64 was compiled but not executed. WASM and RISC-V were not built or executed; the ARM64 single-lane optimizations were not measured natively.

Note

This PR description was drafted with GitHub Copilot.

[azure-pipelines]

Azure Pipelines:
Successfully started running 5 pipeline(s).
11 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[tannergooding]

Ended up going through and looking at all the SIMD related places that might have similar issues and ensuring they're consistent and correct. This looked to be all of them, but it ended up growing the PR compared to the absolute minimal fix.

[Copilot]

Copilot review overview

🔵 Needs a closer look

Three unresolved moderate comments remain in gentree.cpp, requiring fixes and human review.

Review tier: Lite
Findings: None

What changed in this PR

This PR preserves SIMD operand evaluation order and observable effects during JIT folding and decomposition for issue #133718.

Changes:

• Adds observable-effect tracking and ordering-aware SIMD builders.
• Preserves evaluation order across shifts, element operations, stores, Min/Max folding, and platform-specific paths.
• Adds regression coverage for affected evaluation-order cases.

File	Summary
src/​tests/​JIT/​Regression_ro_2/​Runtime_133718.cs	Adds SIMD evaluation-order regression tests.
src/​coreclr/​jit/​optimizer.cpp	Uses observable-effect tracking during optimization.
src/​coreclr/​jit/​optimizebools.cpp	Updates effect checks for boolean optimization.
src/​coreclr/​jit/​morph.cpp	Preserves effects when folding operations.
src/​coreclr/​jit/​lclmorph.cpp	Handles reversed evaluation order during local-store morphing.
src/​coreclr/​jit/​importercalls.cpp	Preserves RISC-V Min/Max operand order.
src/​coreclr/​jit/​importer.cpp	Updates inline argument effect tracking.
src/​coreclr/​jit/​ifconversion.cpp	Uses observable effects during if-conversion.
src/​coreclr/​jit/​hwintrinsicxarch.cpp	Updates xarch intrinsic effect handling.
src/​coreclr/​jit/​hwintrinsic.cpp	Adjusts SIMD sequence, division, and store importing.
src/​coreclr/​jit/​gentree.h	Defines observable-effect flags.
src/​coreclr/​jit/​gentree.cpp	Implements ordering-aware SIMD folding and builders. Three moderate comments remain about materializing address-exposed operands before duplication.
src/​coreclr/​jit/​compiler.h	Extends SIMD store-builder declarations.

[Copilot]

Copilot review overview

🔵 Needs a closer look

Broad cross-platform JIT changes require final human review; several platforms were not executed and focused coverage remains requested.

Review tier: Lite
Findings: None