[llvm] [DAGCombiner] Remove `NoSignedZerosFPMath` uses in `visitFADD` (PR #160635)

[via llvm-commits]

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@@ -879,149 +879,23 @@ define amdgpu_kernel void @v_fneg_add_multi_use_fneg_x_f32(ptr addrspace(1) %out
   ret void
 }
 
-; This one asserted with -enable-no-signed-zeros-fp-math
 define amdgpu_ps float @fneg_fadd_0(float inreg %tmp2, float inreg %tmp6, <4 x i32> %arg) local_unnamed_addr #0 {
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paperchalice wrote:

It loses the coverage indeed, in fact I don't know how to combine them, it has 3 cases: safe, nsz only and fast. 

https://github.com/llvm/llvm-project/pull/160635