[llvm] Reapply [AMDGPU] Avoid resource propagation for recursion through multiple functions (PR #112251)

[Janek van Oirschot via llvm-commits]

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@@ -91,13 +91,76 @@ MCSymbol *MCResourceInfo::getMaxSGPRSymbol(MCContext &OutContext) {
   return OutContext.getOrCreateSymbol("amdgpu.max_num_sgpr");
 }
 
+// The (partially complete) expression should have no recursion in it. After
+// all, we're trying to avoid recursion using this codepath. Returns true if
+// Sym is found within Expr without recursing on Expr, false otherwise.
+static bool findSymbolInExpr(MCSymbol *Sym, const MCExpr *Expr,
+                             SmallVectorImpl<const MCExpr *> &Exprs,
+                             SmallPtrSetImpl<const MCExpr *> &Visited) {
+  // Skip duplicate visits
+  if (!Visited.insert(Expr).second)
+    return false;
+
+  switch (Expr->getKind()) {
+  default:
+    return false;
+  case MCExpr::ExprKind::SymbolRef: {
+    const MCSymbolRefExpr *SymRefExpr = cast<MCSymbolRefExpr>(Expr);
+    const MCSymbol &SymRef = SymRefExpr->getSymbol();
+    if (Sym == &SymRef)
+      return true;
+    if (SymRef.isVariable())
+      Exprs.push_back(SymRef.getVariableValue(/*isUsed=*/false));
+    return false;
+  }
+  case MCExpr::ExprKind::Binary: {
+    const MCBinaryExpr *BExpr = cast<MCBinaryExpr>(Expr);
+    Exprs.push_back(BExpr->getLHS());
+    Exprs.push_back(BExpr->getRHS());
+    return false;
+  }
+  case MCExpr::ExprKind::Unary: {
+    const MCUnaryExpr *UExpr = cast<MCUnaryExpr>(Expr);
+    Exprs.push_back(UExpr->getSubExpr());
+    return false;
+  }
+  case MCExpr::ExprKind::Target: {
+    const AMDGPUMCExpr *AGVK = cast<AMDGPUMCExpr>(Expr);
+    for (const MCExpr *E : AGVK->getArgs())
+      Exprs.push_back(E);
+    return false;
+  }
+  }
+}
+
+// Symbols whose values eventually are used through their defines (i.e.,
+// recursive) must be avoided. Do a walk over Expr to see if Sym will occur in
+// it. The Expr is an MCExpr given through a callee's equivalent MCSymbol so if
+// no recursion is found Sym can be safely assigned to a (sub-)expr which
+// contains the symbol Expr is associated with. Returns true if Sym exists
+// in Expr or its sub-expressions, false otherwise.
+static bool foundRecursiveSymbolDef(MCSymbol *Sym, const MCExpr *Expr) {
+  SmallVector<const MCExpr *, 8> WorkList;
+  SmallPtrSet<const MCExpr *, 8> Visited;
----------------
JanekvO wrote:

Unfortunately, I wasn't able to remove the `Seen` function set as creating a new `MCSymbolRefExpr` will always be unique, even if the same `MCSymbol` is used. This means that the new `WorkSet` wouldn't detect the duplicate and the function resource info expressions may end up with duplicate callees' resource info.

https://github.com/llvm/llvm-project/pull/112251