Issue #32 solution

[ishangtxl]

This commit introduces a new debugging flag, -debug-pass-list, to provide a simple, user-friendly way to view the sequence of passes being run by the New Pass Manager for a given optimization level.

This feature is implemented for the New Pass Manager by:

• Adding a new boolean cl::opt named DebugPassList.
• Hooking into StandardInstrumentations::registerCallbacks to register a BeforeNonSkippedPassCallback.
• When -debug-pass-list is active, the callback gets the name of each pass and prints it.
• Filtering logic has been included to exclude "Adaptor" and "Wrapper" passes to keep the list focused on the core transformations.

First, create a test file

echo 'int main() { return 0; }' > test.c

Run with the new flag at different optimization levels

./bin/clang --sysroot $(xcrun --show-sdk-path) -O2 -mllvm -debug-pass-list test.c -S -o /dev/null
./bin/clang --sysroot $(xcrun --show-sdk-path) -O3 -mllvm -debug-pass-list test.c -S -o /dev/null

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[frederick-vs-ja]

I don't think this file should be changed.