[llvm] Reapply [AMDGPU] Avoid resource propagation for recursion through multiple functions (PR #112251)
Janek van Oirschot via llvm-commits
llvm-commits at lists.llvm.org
Tue Oct 15 08:54:45 PDT 2024
================
@@ -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
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