[RISCV][GISel] Disable call lowering for integers larger than 2*XLen.

[topperc]

Types larger than 2*XLen are passed indirectly which is not supported yet. Currently, we will incorrectly pass X10 multiple times.

[llvmbot]

@llvm/pr-subscribers-backend-risc-v

Author: Craig Topper (topperc)

Changes

Types larger than 2*XLen are passed indirectly which is not supported yet. Currently, we will incorrectly pass X10 multiple times.

---

Full diff: https://github.com/llvm/llvm-project/pull/69144.diff

1 Files Affected:

• (modified) llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp (+48-18)

diff --git a/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp b/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
index a362a709329d5df..74eb4cc8565e553 100644
--- a/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
+++ b/llvm/lib/Target/RISCV/GISel/RISCVCallLowering.cpp
@@ -153,6 +153,42 @@ struct RISCVCallReturnHandler : public RISCVIncomingValueHandler {
 RISCVCallLowering::RISCVCallLowering(const RISCVTargetLowering &TLI)
     : CallLowering(&TLI) {}
 
+// TODO: Support all argument types.
+static bool isSupportedArgumentType(Type *T, const RISCVSubtarget &Subtarget) {
+  // TODO: Integers larger than 2*XLen are passed indirectly which is not
+  // supported yet.
+  if (T->isIntegerTy())
+    return T->getIntegerBitWidth() <= Subtarget.getXLen() * 2;
+  if (T->isPointerTy())
+    return true;
+  return false;
+}
+
+// TODO: Only integer, pointer and aggregate types are supported now.
+static bool isSupportedReturnType(Type *T, const RISCVSubtarget &Subtarget) {
+  // TODO: Integers larger than 2*XLen are passed indirectly which is not
+  // supported yet.
+  if (T->isIntegerTy())
+    return T->getIntegerBitWidth() <= Subtarget.getXLen() * 2;
+  if (T->isPointerTy())
+    return true;
+
+  if (T->isArrayTy())
+    return isSupportedReturnType(T->getArrayElementType(), Subtarget);
+
+  if (T->isStructTy()) {
+    // For now we only allow homogeneous structs that we can manipulate with
+    // G_MERGE_VALUES and G_UNMERGE_VALUES
+    auto StructT = cast<StructType>(T);
+    for (unsigned i = 1, e = StructT->getNumElements(); i != e; ++i)
+      if (StructT->getElementType(i) != StructT->getElementType(0))
+        return false;
+    return isSupportedReturnType(StructT->getElementType(0), Subtarget);
+  }
+
+  return false;
+}
+
 bool RISCVCallLowering::lowerReturnVal(MachineIRBuilder &MIRBuilder,
                                        const Value *Val,
                                        ArrayRef<Register> VRegs,
@@ -160,8 +196,9 @@ bool RISCVCallLowering::lowerReturnVal(MachineIRBuilder &MIRBuilder,
   if (!Val)
     return true;
 
-  // TODO: Only integer, pointer and aggregate types are supported now.
-  if (!Val->getType()->isIntOrPtrTy() && !Val->getType()->isAggregateType())
+  const RISCVSubtarget &Subtarget =
+      MIRBuilder.getMF().getSubtarget<RISCVSubtarget>();
+  if (!isSupportedReturnType(Val->getType(), Subtarget))
     return false;
 
   MachineFunction &MF = MIRBuilder.getMF();
@@ -208,13 +245,11 @@ bool RISCVCallLowering::lowerFormalArguments(MachineIRBuilder &MIRBuilder,
   if (F.isVarArg())
     return false;
 
-  // TODO: Support all argument types.
+  const RISCVSubtarget &Subtarget =
+      MIRBuilder.getMF().getSubtarget<RISCVSubtarget>();
   for (auto &Arg : F.args()) {
-    if (Arg.getType()->isIntegerTy())
-      continue;
-    if (Arg.getType()->isPointerTy())
-      continue;
-    return false;
+    if (!isSupportedArgumentType(Arg.getType(), Subtarget))
+      return false;
   }
 
   MachineFunction &MF = MIRBuilder.getMF();
@@ -252,15 +287,11 @@ bool RISCVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
   const Function &F = MF.getFunction();
   CallingConv::ID CC = F.getCallingConv();
 
-  // TODO: Support all argument types.
+  const RISCVSubtarget &Subtarget =
+      MIRBuilder.getMF().getSubtarget<RISCVSubtarget>();
   for (auto &AInfo : Info.OrigArgs) {
-    if (AInfo.Ty->isIntegerTy())
-      continue;
-    if (AInfo.Ty->isPointerTy())
-      continue;
-    if (AInfo.Ty->isFloatingPointTy())
-      continue;
-    return false;
+    if (!isSupportedArgumentType(AInfo.Ty, Subtarget))
+      return false;
   }
 
   SmallVector<ArgInfo, 32> SplitArgInfos;
@@ -297,8 +328,7 @@ bool RISCVCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
   if (Info.OrigRet.Ty->isVoidTy())
     return true;
 
-  // TODO: Only integer, pointer and aggregate types are supported now.
-  if (!Info.OrigRet.Ty->isIntOrPtrTy() && !Info.OrigRet.Ty->isAggregateType())
+  if (!isSupportedReturnType(Info.OrigRet.Ty, Subtarget))
     return false;
 
   SmallVector<ArgInfo, 4> SplitRetInfos;

[preames]

LGTM

[preames]

I think we're going to need a restriction on array and struct size here as well, but that can be a follow up patch.