[LLVM][IR] Add textual shorthand for specifying constant vector splats.

llvm/docs/LangRef.rst

@@ -4299,6 +4299,11 @@ constants and smaller complex constants.
     "``< i32 42, i32 11, i32 74, i32 100 >``". Vector constants
     must have :ref:`vector type <t_vector>`, and the number and types of
     elements must match those specified by the type.
+
+    When creating a vector whose elements have the same constant value, the
+    preferred syntax is ``splat (<Ty> Val)``. For example: "``splat (i32 11)``".
+    These vector constants must have ::ref:`vector type <t_vector>` with an
+    element type that matches the ``splat`` operand.
 **Zero initialization**
     The string '``zeroinitializer``' can be used to zero initialize a
     value to zero of *any* type, including scalar and

llvm/include/llvm/AsmParser/LLParser.h

@@ -64,6 +64,7 @@ namespace llvm {
       t_Poison,              // No value.
       t_EmptyArray,          // No value:  []
       t_Constant,            // Value in ConstantVal.
+      t_ConstantSplat,       // Value in ConstantVal.
       t_InlineAsm,           // Value in FTy/StrVal/StrVal2/UIntVal.
       t_ConstantStruct,      // Value in ConstantStructElts.
       t_PackedConstantStruct // Value in ConstantStructElts.

llvm/include/llvm/AsmParser/LLToken.h

@@ -336,6 +336,7 @@ enum Kind {
   kw_extractelement,
   kw_insertelement,
   kw_shufflevector,
+  kw_splat,
   kw_extractvalue,
   kw_insertvalue,
   kw_blockaddress,

llvm/lib/AsmParser/LLLexer.cpp

@@ -698,6 +698,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(uinc_wrap);
   KEYWORD(udec_wrap);
 
+  KEYWORD(splat);
   KEYWORD(vscale);
   KEYWORD(x);
   KEYWORD(blockaddress);

llvm/lib/AsmParser/LLParser.cpp

@@ -3981,6 +3981,21 @@ bool LLParser::parseValID(ValID &ID, PerFunctionState *PFS, Type *ExpectedTy) {
     return false;
   }
 
+  case lltok::kw_splat: {
+    Lex.Lex();
+    if (parseToken(lltok::lparen, "expected '(' after vector splat"))
+      return true;
+    Constant *C;
+    if (parseGlobalTypeAndValue(C))
+      return true;
+    if (parseToken(lltok::rparen, "expected ')' at end of vector splat"))
+      return true;
+
+    ID.ConstantVal = C;
+    ID.Kind = ValID::t_ConstantSplat;
+    return false;
+  }
+
   case lltok::kw_getelementptr:
   case lltok::kw_shufflevector:
   case lltok::kw_insertelement:
@@ -5824,6 +5839,17 @@ bool LLParser::convertValIDToValue(Type *Ty, ValID &ID, Value *&V,
                                "' but expected '" + getTypeString(Ty) + "'");
     V = ID.ConstantVal;
     return false;
+  case ValID::t_ConstantSplat:
+    if (!Ty->isVectorTy())
+      return error(ID.Loc, "vector constant must have vector type");
+    if (ID.ConstantVal->getType() != Ty->getScalarType())
+      return error(ID.Loc, "constant expression type mismatch: got type '" +
+                               getTypeString(ID.ConstantVal->getType()) +
+                               "' but expected '" +
+                               getTypeString(Ty->getScalarType()) + "'");
+    V = ConstantVector::getSplat(cast<VectorType>(Ty)->getElementCount(),
+                                 ID.ConstantVal);
+    return false;
   case ValID::t_ConstantStruct:
   case ValID::t_PackedConstantStruct:
     if (StructType *ST = dyn_cast<StructType>(Ty)) {
@@ -5861,6 +5887,7 @@ bool LLParser::parseConstantValue(Type *Ty, Constant *&C) {
   case ValID::t_APFloat:
   case ValID::t_Undef:
   case ValID::t_Constant:
+  case ValID::t_ConstantSplat:
   case ValID::t_ConstantStruct:
   case ValID::t_PackedConstantStruct: {
     Value *V;

llvm/test/Assembler/constant-splat-diagnostics.ll

@@ -0,0 +1,40 @@
+; RUN: rm -rf %t && split-file %s %t
+
+; RUN: not llvm-as < %t/not_a_constant.ll -o /dev/null 2>&1 | FileCheck -check-prefix=NOT_A_CONSTANT %s
+; RUN: not llvm-as < %t/not_a_sclar.ll -o /dev/null 2>&1 | FileCheck -check-prefix=NOT_A_SCALAR %s
+; RUN: not llvm-as < %t/not_a_vector.ll -o /dev/null 2>&1 | FileCheck -check-prefix=NOT_A_VECTOR %s
+; RUN: not llvm-as < %t/wrong_explicit_type.ll -o /dev/null 2>&1 | FileCheck -check-prefix=WRONG_EXPLICIT_TYPE %s
+; RUN: not llvm-as < %t/wrong_implicit_type.ll -o /dev/null 2>&1 | FileCheck -check-prefix=WRONG_IMPLICIT_TYPE %s
+
+;--- not_a_constant.ll
+; NOT_A_CONSTANT: error: expected instruction opcode
+define <4 x i32> @not_a_constant(i32 %a) {
+  %splat = splat (i32 %a)
+  ret <vscale x 4 x i32> %splat
+}
+
+;--- not_a_sclar.ll
+; NOT_A_SCALAR: error: constant expression type mismatch: got type '<1 x i32>' but expected 'i32'
+define <4 x i32> @not_a_scalar() {
+  ret <4 x i32> splat (<1 x i32> <i32 7>)
+}
+
+;--- not_a_vector.ll
+; NOT_A_VECTOR: error: vector constant must have vector type
+define <4 x i32> @not_a_vector() {
+  ret i32 splat (i32 7)
+}
+
+;--- wrong_explicit_type.ll
+; WRONG_EXPLICIT_TYPE: error: constant expression type mismatch: got type 'i8' but expected 'i32'
+define <4 x i32> @wrong_explicit_type() {
+  ret <4 x i32> splat (i8 7)
+}
+
+;--- wrong_implicit_type.ll
+; WRONG_IMPLICIT_TYPE: error: constant expression type mismatch: got type 'i8' but expected 'i32'
+define void @wrong_implicit_type(<4 x i32> %a) {
+  %add = add <4 x i32> %a, splat (i8 7)
+  ret void
+}
+

llvm/test/Assembler/constant-splat.ll

@@ -0,0 +1,67 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis | FileCheck %s
+
+; NOTE: Tests the expansion of the "splat" shorthand method to create vector
+; constants.  Future work will change how "splat" is expanded, ultimately
+; leading to a point where "splat" is emitted as the disassembly.
+
+@my_global = external global i32
+
+; CHECK: @constant.splat.i1 = constant <1 x i1> <i1 true>
+@constant.splat.i1 = constant <1 x i1> splat (i1 true)
+
+; CHECK: @constant.splat.i32 = constant <5 x i32> <i32 7, i32 7, i32 7, i32 7, i32 7>
+@constant.splat.i32 = constant <5 x i32> splat (i32 7)
+
+; CHECK: @constant.splat.i128 = constant <2 x i128> <i128 85070591730234615870450834276742070272, i128 85070591730234615870450834276742070272>
+@constant.splat.i128 = constant <2 x i128> splat (i128 85070591730234615870450834276742070272)
+
+; CHECK: @constant.splat.f16 = constant <4 x half> <half 0xHBC00, half 0xHBC00, half 0xHBC00, half 0xHBC00>
+@constant.splat.f16 = constant <4 x half> splat (half 0xHBC00)
+
+; CHECK: @constant.splat.f32 = constant <5 x float> <float -2.000000e+00, float -2.000000e+00, float -2.000000e+00, float -2.000000e+00, float -2.000000e+00>
+@constant.splat.f32 = constant <5 x float> splat (float -2.000000e+00)
+
+; CHECK: @constant.splat.f64 = constant <3 x double> <double -3.000000e+00, double -3.000000e+00, double -3.000000e+00>
+@constant.splat.f64 = constant <3 x double> splat (double -3.000000e+00)
+
+; CHECK: @constant.splat.128 = constant <2 x fp128> <fp128 0xL00000000000000018000000000000000, fp128 0xL00000000000000018000000000000000>
+@constant.splat.128 = constant <2 x fp128> splat (fp128 0xL00000000000000018000000000000000)
+
+; CHECK: @constant.splat.bf16 = constant <4 x bfloat> <bfloat 0xRC0A0, bfloat 0xRC0A0, bfloat 0xRC0A0, bfloat 0xRC0A0>
+@constant.splat.bf16 = constant <4 x bfloat> splat (bfloat 0xRC0A0)
+
+; CHECK: @constant.splat.x86_fp80 = constant <3 x x86_fp80> <x86_fp80 0xK4000C8F5C28F5C28F800, x86_fp80 0xK4000C8F5C28F5C28F800, x86_fp80 0xK4000C8F5C28F5C28F800>
+@constant.splat.x86_fp80 = constant <3 x x86_fp80> splat (x86_fp80 0xK4000C8F5C28F5C28F800)
+
+; CHECK: @constant.splat.ppc_fp128 = constant <1 x ppc_fp128> <ppc_fp128 0xM80000000000000000000000000000000>
+@constant.splat.ppc_fp128 = constant <1 x ppc_fp128> splat (ppc_fp128 0xM80000000000000000000000000000000)
+
+; CHECK: @constant.splat.global.ptr = constant <4 x ptr> <ptr @my_global, ptr @my_global, ptr @my_global, ptr @my_global>
+@constant.splat.global.ptr = constant <4 x ptr> splat (ptr @my_global)
+
+define void @add_fixed_lenth_vector_splat_i32(<4 x i32> %a) {
+; CHECK: %add = add <4 x i32> %a, <i32 137, i32 137, i32 137, i32 137>
+  %add = add <4 x i32> %a, splat (i32 137)
+  ret void
+}
+
+define <4 x i32> @ret_fixed_lenth_vector_splat_i32() {
+; CHECK: ret <4 x i32> <i32 56, i32 56, i32 56, i32 56>
+  ret <4 x i32> splat (i32 56)
+}
+
+define void @add_fixed_lenth_vector_splat_double(<vscale x 2 x double> %a) {
+; CHECK: %add = fadd <vscale x 2 x double> %a, shufflevector (<vscale x 2 x double> insertelement (<vscale x 2 x double> poison, double 5.700000e+00, i64 0), <vscale x 2 x double> poison, <vscale x 2 x i32> zeroinitializer)
+  %add = fadd <vscale x 2 x double> %a, splat (double 5.700000e+00)
+  ret void
+}
+
+define <vscale x 4 x i32> @ret_scalable_vector_splat_i32() {
+; CHECK: ret <vscale x 4 x i32> shufflevector (<vscale x 4 x i32> insertelement (<vscale x 4 x i32> poison, i32 78, i64 0), <vscale x 4 x i32> poison, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 4 x i32> splat (i32 78)
+}
+
+define <vscale x 4 x ptr> @ret_scalable_vector_ptr() {
+; CHECK: ret <vscale x 4 x ptr> shufflevector (<vscale x 4 x ptr> insertelement (<vscale x 4 x ptr> poison, ptr @my_global, i64 0), <vscale x 4 x ptr> poison, <vscale x 4 x i32> zeroinitializer)
+  ret <vscale x 4 x ptr> splat (ptr @my_global)
+}