How can I find what instruction set extension is supported in my Intel Processor?

https://www.intel.com/content/www/us/en/support/articles/000005779/processors.html

1. Go to https://ark.intel.com/content/www/us/en/ark.html site
2. Processors
3. Select Intel xxx Processor type
4. Select Product Name: Intel® Core™ i7-5500U Processor
5. Find "Advanced Technology"
You can find the supported SIMD instructions
 Intel i7-5500U can support: Intel® SSE4.1, Intel® SSE4.2, Intel® AVX2

And 
How to Identify My Intel® Processor
And gcc x86 options
https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html