[llvm] Revert "[MIPS]Fix QNaNs in the MIPS legacy NaN encodings" (PR #150773)

[Matt Arsenault via llvm-commits]

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@@ -1,14 +0,0 @@
-; RUN: llc -O3 -mcpu=mips32r2 -mtriple=mips-linux-gnu < %s -o - | FileCheck %s -check-prefixes=MIPS_Legacy
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arsenm wrote:

Should restore the test, but drop the -O3 and test the preserved behavior 

https://github.com/llvm/llvm-project/pull/150773