[llvm] [IA]: Construct (de)interleave4 out of (de)interleave2 (PR #89276)

[Paul Walker via llvm-commits]

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@@ -16585,17 +16585,87 @@ bool AArch64TargetLowering::lowerInterleavedStore(StoreInst *SI,
   return true;
 }
 
+bool getDeinterleavedValues(Value *DI,
+                            SmallVectorImpl<Instruction *> &DeinterleavedValues) {
+  if (!DI->hasNUsesOrMore(2))
+    return false;
+  auto *Extr1 = dyn_cast<ExtractValueInst>(*(DI->user_begin()));
+  auto *Extr2 = dyn_cast<ExtractValueInst>(*(++DI->user_begin()));
+  if (!Extr1 || !Extr2)
+    return false;
+
+  if (!Extr1->hasNUsesOrMore(1) || !Extr2->hasNUsesOrMore(1))
+    return false;
+  auto *DI1 = *(Extr1->user_begin());
+  auto *DI2 = *(Extr2->user_begin());
+
+  if (!DI1->hasNUsesOrMore(2) || !DI2->hasNUsesOrMore(2))
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paulwalker-arm wrote:

As above.

https://github.com/llvm/llvm-project/pull/89276