[llvm] [Matrix] Propagate shape information through Select insts (PR #141876)

[Jon Roelofs via llvm-commits]

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@@ -269,6 +269,15 @@ computeShapeInfoForInst(Instruction *I,
       return OpShape->second;
   }
 
+  if (isa<SelectInst>(I)) {
+    auto OpShape = ShapeMap.find(I->getOperand(1));
+    if (OpShape != ShapeMap.end())
+      return OpShape->second;
+    OpShape = ShapeMap.find(I->getOperand(2));
+    if (OpShape != ShapeMap.end())
+      return OpShape->second;
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jroelofs wrote:

I think it should _almost_ match, but not quite: we need to ignore the condition operand for shape info iff it is not a vector.

https://github.com/llvm/llvm-project/pull/141876