[SDPatternMatch] Do not use std::forward and rvalue references (NFC) (#93806)

The m_ZExtOrSelf() family of matchers currently incorrectly calls
std::forward twice on the same value. However, just removing those causes
other complications, because then template arguments get incorrectly
inferred to const references instead of the underlying value types.
Things become a mess.

Instead, just completely remove the use of std::forward and rvalue
references from SDPatternMatch. I don't think they really provide value
in this context, especially as they're not used consistently in the
first place.

Author: nikic

llvm/include/llvm/CodeGen/SDPatternMatch.h

@@ -330,9 +330,7 @@ template <typename... Preds> struct And {
 template <typename Pred, typename... Preds>
 struct And<Pred, Preds...> : And<Preds...> {
   Pred P;
-  And(Pred &&p, Preds &&...preds)
-      : And<Preds...>(std::forward<Preds>(preds)...), P(std::forward<Pred>(p)) {
-  }
+  And(const Pred &p, const Preds &...preds) : And<Preds...>(preds...), P(p) {}
 
   template <typename MatchContext>
   bool match(const MatchContext &Ctx, SDValue N) {
@@ -349,8 +347,7 @@ template <typename... Preds> struct Or {
 template <typename Pred, typename... Preds>
 struct Or<Pred, Preds...> : Or<Preds...> {
   Pred P;
-  Or(Pred &&p, Preds &&...preds)
-      : Or<Preds...>(std::forward<Preds>(preds)...), P(std::forward<Pred>(p)) {}
+  Or(const Pred &p, const Preds &...preds) : Or<Preds...>(preds...), P(p) {}
 
   template <typename MatchContext>
   bool match(const MatchContext &Ctx, SDValue N) {
@@ -376,16 +373,16 @@ template <typename Pred> inline Not<Pred> m_Unless(const Pred &P) {
   return Not{P};
 }
 
-template <typename... Preds> And<Preds...> m_AllOf(Preds &&...preds) {
-  return And<Preds...>(std::forward<Preds>(preds)...);
+template <typename... Preds> And<Preds...> m_AllOf(const Preds &...preds) {
+  return And<Preds...>(preds...);
 }
 
-template <typename... Preds> Or<Preds...> m_AnyOf(Preds &&...preds) {
-  return Or<Preds...>(std::forward<Preds>(preds)...);
+template <typename... Preds> Or<Preds...> m_AnyOf(const Preds &...preds) {
+  return Or<Preds...>(preds...);
 }
 
-template <typename... Preds> auto m_NoneOf(Preds &&...preds) {
-  return m_Unless(m_AnyOf(std::forward<Preds>(preds)...));
+template <typename... Preds> auto m_NoneOf(const Preds &...preds) {
+  return m_Unless(m_AnyOf(preds...));
 }
 
 // === Generic node matching ===
@@ -402,10 +399,8 @@ struct Operands_match<OpIdx, OpndPred, OpndPreds...>
     : Operands_match<OpIdx + 1, OpndPreds...> {
   OpndPred P;
 
-  Operands_match(OpndPred &&p, OpndPreds &&...preds)
-      : Operands_match<OpIdx + 1, OpndPreds...>(
-            std::forward<OpndPreds>(preds)...),
-        P(std::forward<OpndPred>(p)) {}
+  Operands_match(const OpndPred &p, const OpndPreds &...preds)
+      : Operands_match<OpIdx + 1, OpndPreds...>(preds...), P(p) {}
 
   template <typename MatchContext>
   bool match(const MatchContext &Ctx, SDValue N) {
@@ -419,9 +414,8 @@ struct Operands_match<OpIdx, OpndPred, OpndPreds...>
 };
 
 template <typename... OpndPreds>
-auto m_Node(unsigned Opcode, OpndPreds &&...preds) {
-  return m_AllOf(m_Opc(Opcode), Operands_match<0, OpndPreds...>(
-                                    std::forward<OpndPreds>(preds)...));
+auto m_Node(unsigned Opcode, const OpndPreds &...preds) {
+  return m_AllOf(m_Opc(Opcode), Operands_match<0, OpndPreds...>(preds...));
 }
 
 /// Provide number of operands that are not chain or glue, as well as the first
@@ -647,10 +641,9 @@ template <typename Opnd> inline UnaryOpc_match<Opnd> m_ZExt(const Opnd &Op) {
   return UnaryOpc_match<Opnd>(ISD::ZERO_EXTEND, Op);
 }
 
-template <typename Opnd> inline auto m_SExt(Opnd &&Op) {
-  return m_AnyOf(
-      UnaryOpc_match<Opnd>(ISD::SIGN_EXTEND, Op),
-      m_Node(ISD::SIGN_EXTEND_INREG, std::forward<Opnd>(Op), m_Value()));
+template <typename Opnd> inline auto m_SExt(const Opnd &Op) {
+  return m_AnyOf(UnaryOpc_match<Opnd>(ISD::SIGN_EXTEND, Op),
+                 m_Node(ISD::SIGN_EXTEND_INREG, Op, m_Value()));
 }
 
 template <typename Opnd> inline UnaryOpc_match<Opnd> m_AnyExt(const Opnd &Op) {
@@ -663,30 +656,28 @@ template <typename Opnd> inline UnaryOpc_match<Opnd> m_Trunc(const Opnd &Op) {
 
 /// Match a zext or identity
 /// Allows to peek through optional extensions
-template <typename Opnd> inline auto m_ZExtOrSelf(Opnd &&Op) {
-  return m_AnyOf(m_ZExt(std::forward<Opnd>(Op)), std::forward<Opnd>(Op));
+template <typename Opnd> inline auto m_ZExtOrSelf(const Opnd &Op) {
+  return m_AnyOf(m_ZExt(Op), Op);
 }
 
 /// Match a sext or identity
 /// Allows to peek through optional extensions
-template <typename Opnd> inline auto m_SExtOrSelf(Opnd &&Op) {
-  return m_AnyOf(m_SExt(std::forward<Opnd>(Op)), std::forward<Opnd>(Op));
+template <typename Opnd> inline auto m_SExtOrSelf(const Opnd &Op) {
+  return m_AnyOf(m_SExt(Op), Op);
 }
 
 /// Match a aext or identity
 /// Allows to peek through optional extensions
 template <typename Opnd>
-inline Or<UnaryOpc_match<Opnd>, Opnd> m_AExtOrSelf(Opnd &&Op) {
-  return Or<UnaryOpc_match<Opnd>, Opnd>(m_AnyExt(std::forward<Opnd>(Op)),
-                                        std::forward<Opnd>(Op));
+inline Or<UnaryOpc_match<Opnd>, Opnd> m_AExtOrSelf(const Opnd &Op) {
+  return Or<UnaryOpc_match<Opnd>, Opnd>(m_AnyExt(Op), Op);
 }
 
 /// Match a trunc or identity
 /// Allows to peek through optional truncations
 template <typename Opnd>
-inline Or<UnaryOpc_match<Opnd>, Opnd> m_TruncOrSelf(Opnd &&Op) {
-  return Or<UnaryOpc_match<Opnd>, Opnd>(m_Trunc(std::forward<Opnd>(Op)),
-                                        std::forward<Opnd>(Op));
+inline Or<UnaryOpc_match<Opnd>, Opnd> m_TruncOrSelf(const Opnd &Op) {
+  return Or<UnaryOpc_match<Opnd>, Opnd>(m_Trunc(Op), Op);
 }
 
 // === Constants ===