[llvm] [LSR] Recognize vscale-relative immediates (PR #88124)

[Graham Hunter via llvm-commits]

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@@ -3887,15 +4027,26 @@ void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
 /// Helper function for LSRInstance::GenerateConstantOffsets.
 void LSRInstance::GenerateConstantOffsetsImpl(
     LSRUse &LU, unsigned LUIdx, const Formula &Base,
-    const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
+    const SmallVectorImpl<Immediate> &Worklist, size_t Idx, bool IsScaledReg) {
 
-  auto GenerateOffset = [&](const SCEV *G, int64_t Offset) {
+  auto GenerateOffset = [&](const SCEV *G, Immediate Offset) {
     Formula F = Base;
-    F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
+    if (Base.BaseOffset.isScalable() != Offset.isScalable() &&
+        Base.BaseOffset.isNonZero() && Offset.isNonZero())
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huntergr-arm wrote:

Yeah, I treat them that way as well. But this is checking for scalability being equal _if_ both are nonzero. I guess an 'isCompatible()' helper might be better (subject to bikeshedding over the name).

https://github.com/llvm/llvm-project/pull/88124