[sycl-post-link] Several fixes for 'default' spec constants (#4649)

Fixed collection of default values of `half` scalar spec constants in
`SpecConstantsPass` as well as handling of vectors and arrays there.

llvm/test/tools/sycl-post-link/spec-constants/SYCL-2020.ll

@@ -1,7 +1,9 @@
-; RUN: sycl-post-link --ir-output-only -spec-const=default %s -S -o - | \
-; RUN:   FileCheck %s -check-prefixes=CHECK,CHECK-DEF
-; RUN: sycl-post-link --ir-output-only -spec-const=rt %s -S -o - | \
-; RUN:   FileCheck %s -check-prefixes=CHECK,CHECK-RT
+; RUN: sycl-post-link -spec-const=default %s -S -o %t.table
+; RUN: FileCheck %s -check-prefixes=CHECK,CHECK-DEF < %t_0.ll
+; RUN: FileCheck %s --check-prefixes=CHECK-PROPS,CHECK-PROPS-DEF < %t_0.prop
+; RUN: sycl-post-link -spec-const=rt %s -S -o %t.table
+; RUN: FileCheck %s -check-prefixes=CHECK,CHECK-RT < %t_0.ll
+; RUN: FileCheck %s --check-prefixes=CHECK-PROPS < %t_0.prop
 
 ; This test checks that the post link tool is able to correctly transform
 ; SYCL 2020 specialization constant intrinsics for different types in a device
@@ -241,3 +243,16 @@ attributes #3 = { nounwind }
 ; CHECK-RT-SAME: i32 [[#SCID11]], i32 4, i32 4}
 ; CHECK-RT: ![[#ID5]] = !{!"_ZTS14name_generatorIL_Z10id_marrayEE", i32 [[#SCID12]], i32 0, i32 4,
 ; CHECK-RT-SAME: i32 [[#SCID13]], i32 4, i32 4}
+
+; CHECK-PROPS: [SYCL/specialization constants]
+; CHECK-PROPS: _ZTS14name_generatorIL_Z9id_halfEE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z6id_intEE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z9id_composEE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z10id_compos2EE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z10id_vectorEE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z10id_marrayEE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z10id_marray2EE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z10id_marray3EE=2|
+; CHECK-PROPS: _ZTS14name_generatorIL_Z10id_marray4EE=2|
+; CHECK-PROPS-DEF: [SYCL/specialization constants default values]
+; CHECK-PROPS-DEF: all=2|

llvm/tools/sycl-post-link/SpecConstants.cpp

@@ -297,7 +297,15 @@ void collectCompositeElementsDefaultValuesRecursive(
     const Module &M, Constant *C, unsigned &Offset,
     std::vector<char> &DefaultValues) {
   Type *Ty = C->getType();
-  if (auto *ArrTy = dyn_cast<ArrayType>(Ty)) {
+  if (auto *DataSeqC = dyn_cast<ConstantDataSequential>(C)) {
+    // This code is generic for both vectors and arrays of scalars
+    for (size_t I = 0; I < DataSeqC->getNumElements(); ++I) {
+      Constant *El = cast<Constant>(DataSeqC->getElementAsConstant(I));
+      collectCompositeElementsDefaultValuesRecursive(M, El, Offset,
+                                                     DefaultValues);
+    }
+  } else if (auto *ArrTy = dyn_cast<ArrayType>(Ty)) {
+    // This branch handles arrays of composite types (structs, arrays, etc.)
     for (size_t I = 0; I < ArrTy->getNumElements(); ++I) {
       Constant *El = cast<Constant>(C->getOperand(I));
       collectCompositeElementsDefaultValuesRecursive(M, El, Offset,
@@ -324,12 +332,6 @@ void collectCompositeElementsDefaultValuesRecursive(
     // Update "global" offset according to the total size of a handled struct
     // type.
     Offset += SL->getSizeInBytes();
-  } else if (auto *VecTy = dyn_cast<FixedVectorType>(Ty)) {
-    for (size_t I = 0; I < VecTy->getNumElements(); ++I) {
-      Constant *El = cast<Constant>(C->getOperand(I));
-      collectCompositeElementsDefaultValuesRecursive(M, El, Offset,
-                                                     DefaultValues);
-    }
   } else { // Assume that we encountered some scalar element
     int NumBytes = Ty->getScalarSizeInBits() / CHAR_BIT +
                    (Ty->getScalarSizeInBits() % 8 != 0);
@@ -341,7 +343,13 @@ void collectCompositeElementsDefaultValuesRecursive(
     } else if (auto FPConst = dyn_cast<ConstantFP>(C)) {
       auto Val = FPConst->getValue();
 
-      if (NumBytes == 4) {
+      if (NumBytes == 2) {
+        auto IVal = Val.bitcastToAPInt();
+        assert(IVal.getBitWidth() == 16);
+        auto Storage = static_cast<uint16_t>(IVal.getZExtValue());
+        std::copy_n(reinterpret_cast<char *>(&Storage), NumBytes,
+                    std::back_inserter(DefaultValues));
+      } else if (NumBytes == 4) {
         float v = Val.convertToFloat();
         std::copy_n(reinterpret_cast<char *>(&v), NumBytes,
                     std::back_inserter(DefaultValues));