[llvm] [AArch64][GlobalISel] Adopt some Ld1Lane* patterns for GlobalISel to reduce codegen regressions (PR #69607)

[Pierre van Houtryve via llvm-commits]

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@@ -62,9 +63,16 @@ bool GIMatchTableExecutor::isBaseWithConstantOffset(
 bool GIMatchTableExecutor::isObviouslySafeToFold(MachineInstr &MI,
                                                  MachineInstr &IntoMI) const {
   // Immediate neighbours are already folded.
-  if (MI.getParent() == IntoMI.getParent() &&
-      std::next(MI.getIterator()) == IntoMI.getIterator())
-    return true;
+  // Any G_CONSTANT between immediate neighbours can be ignored.
+  if (MI.getParent() == IntoMI.getParent()) {
+    auto IntoIt = IntoMI.getIterator();
+    auto NextIt = std::next(MI.getIterator());
+    while (!NextIt.isEnd() && NextIt != IntoIt &&
+           NextIt->getOpcode() == TargetOpcode::G_CONSTANT)
+      ++NextIt;
+    if (NextIt == IntoIt)
+      return true;
+  }
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Pierre-vh wrote:

Do you have an example of what this does? Like a code pattern that would be rejected without this change.

https://github.com/llvm/llvm-project/pull/69607