[Frontend][Diagnostics] Improve emitting diagnostic information

[sfzhu93]

Summary

This PR enhances the current implementation for emitting diagnostic remarks by introducing a unified handler in ir.cc. This handler manages diagnostic information more effectively and disables the emission of IRs unless explicitly requested by the user. The MLIR_ENABLE_DIAGNOSTICS environment variable now controls all diagnostic emission settings, accepting one or more values from {warnings, remarks, stacktraces, operations}, separated by commas. Detailed usage instructions are available in the README.

Background

Previously, a new default LLVM SourceManager was configured in nvidia/backend/compiler.py to support remarks, applied in both make_ttgir and make_llir. However, a custom handler already existed in ir.cc, and a more robust design should extend this handler rather than create a new one.

Changes

• Unified Handler: Inspired by LLVM upstream [PR 117669]([MLIR][mlir-opt] add support for disabling diagnostics llvm/llvm-project#117669), this PR implements a similar custom handler that supports various severity levels. The MLIR_ENABLE_DIAGNOSTICS environment variable now specifies the severity level: warnings for warnings and errors, and remarks for remarks, warnings, and errors.

• IR Emission Control: By default, the MLIR diagnostic API emits IRs, which can clutter error messages or performance remarks. This PR suppresses IR emission unless explicitly enabled by the user, improving the readability of error messages and performance remarks. Users can specify MLIR_ENABLE_DIAGNOSTICS=remarks,operations to include IR operations in remarks.

• Stacktraces: Previously, setting MLIR_ENABLE_DIAGNOSTICS=1 enabled all diagnostic information with stacktraces. Now, the stacktraces parameter specifically enables stacktraces. For example, MLIR_ENABLE_DIAGNOSTICS=remarks,operations,stacktraces enables IR operations and stacktraces, displaying all remarks, warnings, and errors.

• Testing: Updated existing Python tests to verify that combinations of operations and stacktraces are emitted successfully.

Future Work

• With the new handler in place, there is an opportunity to further enhance the readability of existing warnings and remarks. This will be a focus in future updates.

New contributor declaration

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    including the "tests should be minimal" section. (Usually running Python code
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[sfzhu93]

Sorry for pinging you for review - I did a wrong merge on my branch.

[manman-ren]

Thanks for cleaning up/restructuring! This PR looks good to me.