[AMDGPU] Add a new function getIntegerPairAttribute (llvm#133271)

The new function will return `std::nullopt` when any error occurs.

Author: shiltian

llvm/lib/Target/AMDGPU/AMDGPULowerKernelAttributes.cpp

@@ -107,7 +107,8 @@ static bool processUse(CallInst *CI, bool IsV5OrAbove) {
     F->getFnAttribute("uniform-work-group-size").getValueAsBool();
 
   SmallVector<unsigned> MaxNumWorkgroups =
-      AMDGPU::getIntegerVecAttribute(*F, "amdgpu-max-num-workgroups", 3);
+      AMDGPU::getIntegerVecAttribute(*F, "amdgpu-max-num-workgroups",
+                                     /*Size=*/3, /*DefaultVal=*/0);
 
   if (!HasReqdWorkGroupSize && !HasUniformWorkGroupSize &&
       none_of(MaxNumWorkgroups, [](unsigned X) { return X != 0; }))

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.cpp

@@ -1398,16 +1398,25 @@ getIntegerPairAttribute(const Function &F, StringRef Name,
 SmallVector<unsigned> getIntegerVecAttribute(const Function &F, StringRef Name,
                                              unsigned Size,
                                              unsigned DefaultVal) {
+  std::optional<SmallVector<unsigned>> R =
+      getIntegerVecAttribute(F, Name, Size);
+  return R.has_value() ? *R : SmallVector<unsigned>(Size, DefaultVal);
+}
+
+std::optional<SmallVector<unsigned>>
+getIntegerVecAttribute(const Function &F, StringRef Name, unsigned Size) {
   assert(Size > 2);
-  SmallVector<unsigned> Default(Size, DefaultVal);
+  LLVMContext &Ctx = F.getContext();
 
   Attribute A = F.getFnAttribute(Name);
-  if (!A.isStringAttribute())
-    return Default;
-
-  SmallVector<unsigned> Vals(Size, DefaultVal);
+  if (!A.isValid())
+    return std::nullopt;
+  if (!A.isStringAttribute()) {
+    Ctx.emitError(Name + " is not a string attribute");
+    return std::nullopt;
+  }
 
-  LLVMContext &Ctx = F.getContext();
+  SmallVector<unsigned> Vals(Size);
 
   StringRef S = A.getValueAsString();
   unsigned i = 0;
@@ -1417,7 +1426,7 @@ SmallVector<unsigned> getIntegerVecAttribute(const Function &F, StringRef Name,
     if (Strs.first.trim().getAsInteger(0, IntVal)) {
       Ctx.emitError("can't parse integer attribute " + Strs.first + " in " +
                     Name);
-      return Default;
+      return std::nullopt;
     }
     Vals[i] = IntVal;
     S = Strs.second;
@@ -1427,7 +1436,7 @@ SmallVector<unsigned> getIntegerVecAttribute(const Function &F, StringRef Name,
     Ctx.emitError("attribute " + Name +
                   " has incorrect number of integers; expected " +
                   llvm::utostr(Size));
-    return Default;
+    return std::nullopt;
   }
   return Vals;
 }

llvm/lib/Target/AMDGPU/Utils/AMDGPUBaseInfo.h

@@ -958,14 +958,14 @@ getIntegerPairAttribute(const Function &F, StringRef Name,
 
 /// \returns Generate a vector of integer values requested using \p F's \p Name
 /// attribute.
-///
-/// \returns true if exactly Size (>2) number of integers are found in the
-/// attribute.
-///
-/// \returns false if any error occurs.
+/// \returns A vector of size \p Size, with all elements set to \p DefaultVal,
+/// if any error occurs. The corresponding error will also be emitted.
 SmallVector<unsigned> getIntegerVecAttribute(const Function &F, StringRef Name,
                                              unsigned Size,
-                                             unsigned DefaultVal = 0);
+                                             unsigned DefaultVal);
+/// Similar to the function above, but returns std::nullopt if any error occurs.
+std::optional<SmallVector<unsigned>>
+getIntegerVecAttribute(const Function &F, StringRef Name, unsigned Size);
 
 /// Represents the counter values to wait for in an s_waitcnt instruction.
 ///