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update README with info about SSE2 on GCC

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Sean Barrett
Sean Barrett committed Mar 20, 2017
1 parent e88fff6 commit c7110588a4d24c4bb5155c184fbb77dd90b3116e
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  1. +16 −0 README.md
  2. +16 −0 tools/README.footer.md
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@@ -58,6 +58,22 @@ dual-license for you to choose from.
No, because it's public domain you can freely relicense it to whatever license your new
library wants to be.
#### What's the deal with SSE support in GCC-based compilers?
stb_image will either use SSE2 (if you compile with -msse2) or
will not use any SIMD at all, rather than trying to detect the
processor at runtime and handle it correctly. As I understand it,
the approved path in GCC for runtime-detection require
you to use multiple source files, one for each CPU configuration.
Because stb_image is a header-file library that compiles in only
one source file, there's no approved way to build both an
SSE-enabled and a non-SSE-enabled variation.
While we've tried to work around it, we've had multiple issues over
the years due to specific versions of gcc breaking what we're doing,
so we've given up on it. See https://github.com/nothings/stb/issues/280
and https://github.com/nothings/stb/issues/410 for examples.
#### Some of these libraries seem redundant to existing open source libraries. Are they better somehow?
Generally they're only better in that they're easier to integrate,
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@@ -21,6 +21,22 @@ dual-license for you to choose from.
No, because it's public domain you can freely relicense it to whatever license your new
library wants to be.
#### What's the deal with SSE support in GCC-based compilers?
stb_image will either use SSE2 (if you compile with -msse2) or
will not use any SIMD at all, rather than trying to detect the
processor at runtime and handle it correctly. As I understand it,
the approved path in GCC for runtime-detection require
you to use multiple source files, one for each CPU configuration.
Because stb_image is a header-file library that compiles in only
one source file, there's no approved way to build both an
SSE-enabled and a non-SSE-enabled variation.
While we've tried to work around it, we've had multiple issues over
the years due to specific versions of gcc breaking what we're doing,
so we've given up on it. See https://github.com/nothings/stb/issues/280
and https://github.com/nothings/stb/issues/410 for examples.
#### Some of these libraries seem redundant to existing open source libraries. Are they better somehow?
Generally they're only better in that they're easier to integrate,

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