[llvm] [InstCombine] Fold fneg/fabs patterns with ppc_f128 (PR #130557)

[Nikita Popov via llvm-commits]

================
@@ -144,9 +147,15 @@ static constexpr fltSemantics semFloat8E4M3B11FNUZ = {
     4, -10, 4, 8, fltNonfiniteBehavior::NanOnly, fltNanEncoding::NegativeZero};
 static constexpr fltSemantics semFloat8E3M4 = {3, -2, 5, 8};
 static constexpr fltSemantics semFloatTF32 = {127, -126, 11, 19};
-static constexpr fltSemantics semFloat8E8M0FNU = {
-    127,   -127, 1, 8, fltNonfiniteBehavior::NanOnly, fltNanEncoding::AllOnes,
-    false, false};
+static constexpr fltSemantics semFloat8E8M0FNU = {127,
+                                                  -127,
+                                                  1,
+                                                  8,
+                                                  fltNonfiniteBehavior::NanOnly,
+                                                  fltNanEncoding::AllOnes,
+                                                  false,
+                                                  false,
+                                                  false};
----------------
nikic wrote:

This makes me wonder though whether we need a separate flag. Can we use hasSignedRepr instead, and specify that hasSignedRepr must have the sign bit in the MSB?

https://github.com/llvm/llvm-project/pull/130557