Regression from llvm-6: llvm-7 replaces 'undef' with 'NaN', and generates NaN at the assembler level - This issue generates black screen on some fragment shaders.

Submitted by Patrick

Assigned to Default DRI bug account

Link to original bug (#109608)

Description

The issue is not related to mesa itself but at the LLVM optimization stage: LLVMRunPassManager(). This bug report is mostly for tracking purposes.

Here are two fragment shaders affected: https://www.shadertoy.com/view/ltl3WS and https://www.shadertoy.com/view/MdVcRd

Here is the LLVM bug report: https://bugs.llvm.org/show_bug.cgi?id=40690

Version: git