[llvm] [InstCombine] Factorise add/sub and max/min using distributivity (PR #101507)

[via llvm-commits]

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@@ -1505,6 +1505,80 @@ foldMinimumOverTrailingOrLeadingZeroCount(Value *I0, Value *I1,
       ConstantInt::getTrue(ZeroUndef->getType()));
 }
 
+/// Return whether "X LOp (Y ROp Z)" is always equal to
+/// "(X LOp Y) ROp (X LOp Z)".
+static bool leftDistributesOverRightIntrinsic(Intrinsic::ID LOp,
+                                              Intrinsic::ID ROp) {
+  switch (LOp) {
+  case Intrinsic::umax:
+    return ROp == Intrinsic::umin;
+  case Intrinsic::smax:
+    return ROp == Intrinsic::smin;
+  case Intrinsic::umin:
+    return ROp == Intrinsic::umax;
+  case Intrinsic::smin:
+    return ROp == Intrinsic::smax;
+  case Intrinsic::uadd_sat:
+    return ROp == Intrinsic::umax || ROp == Intrinsic::umin;
+  case Intrinsic::sadd_sat:
+    return ROp == Intrinsic::smax || ROp == Intrinsic::smin;
+  default:
+    return false;
+  }
+}
+
+// Attempts to factorise a common term
+// in an instruction that has the form "(A op' B) op (C op' D)
+static Instruction *
+foldCallUsingDistributiveLaws(CallInst *II, InstCombiner::BuilderTy &Builder) {
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goldsteinn wrote:

`CallInst` -> `IntrinsicInst`

https://github.com/llvm/llvm-project/pull/101507