[llvm] [InstCombine] Improve bitfield addition (PR #77184)

[via llvm-commits]

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@@ -3379,6 +3379,149 @@ Value *InstCombinerImpl::foldAndOrOfICmps(ICmpInst *LHS, ICmpInst *RHS,
   return foldAndOrOfICmpsUsingRanges(LHS, RHS, IsAnd);
 }
 
+struct BitFieldAddBitMask {
+  const APInt *Lower;
+  const APInt *Upper;
+};
+struct BitFieldOptBitMask {
+  const APInt *Lower;
+  const APInt *Upper;
+  const APInt *New;
+};
+struct BitFieldAddInfo {
+  Value *X;
+  Value *Y;
+  bool opt;
+  union {
+    BitFieldAddBitMask AddMask;
+    BitFieldOptBitMask OptMask;
+  };
+};
+
+static Value *foldBitFieldArithmetic(BinaryOperator &I,
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ParkHanbum wrote:

honestly I have no idea. I focused how to implement your optimization idea in my boundary of llvm knowledge. some advise please to me to let me can think about that. what's mean `terms of more generic canonicalizations or not`?

https://github.com/llvm/llvm-project/pull/77184