[Analysis] add isSplatValue() for vectors in IR

We have the related getSplatValue() already in IR (see code just above the proposed addition).
But sometimes we only need to know that the value is a splat rather than capture the splatted
scalar value. Also, we have an isSplatValue() function already in SDAG.

Motivation - recent bugs that would potentially benefit from improved splat analysis in IR:
https://bugs.llvm.org/show_bug.cgi?id=37428
https://bugs.llvm.org/show_bug.cgi?id=42174

Differential Revision: https://reviews.llvm.org/D63138

llvm-svn: 363106

1 files changed, 190 insertions, 0 deletions

diff --git a/llvm/unittests/Analysis/VectorUtilsTest.cpp b/llvm/unittests/Analysis/VectorUtilsTest.cpp
index 8ff6744bf78..a33fdb503bb 100644
--- a/llvm/unittests/Analysis/VectorUtilsTest.cpp
+++ b/llvm/unittests/Analysis/VectorUtilsTest.cpp
@@ -11,8 +11,10 @@
 #include "llvm/AsmParser/Parser.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/InstIterator.h"
+#include "llvm/IR/IRBuilder.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Module.h"
+#include "llvm/IR/NoFolder.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/SourceMgr.h"
 #include "llvm/Support/KnownBits.h"
@@ -56,8 +58,196 @@ protected:
   Instruction *A;
 };
 
+struct BasicTest : public testing::Test {
+  LLVMContext Ctx;
+  std::unique_ptr<Module> M;
+  Function *F;
+  BasicBlock *BB;
+  IRBuilder<NoFolder> IRB;
+
+  BasicTest()
+      : M(new Module("VectorUtils", Ctx)),
+        F(Function::Create(
+            FunctionType::get(Type::getVoidTy(Ctx), /* IsVarArg */ false),
+            Function::ExternalLinkage, "f", M.get())),
+        BB(BasicBlock::Create(Ctx, "entry", F)), IRB(BB) {}
+};
+
+
 } // namespace
 
+TEST_F(BasicTest, isSplat) {
+  Value *UndefVec = UndefValue::get(VectorType::get(IRB.getInt8Ty(), 4));
+  EXPECT_TRUE(isSplatValue(UndefVec));
+
+  Constant *UndefScalar = UndefValue::get(IRB.getInt8Ty());
+  EXPECT_FALSE(isSplatValue(UndefScalar));
+
+  Constant *ScalarC = IRB.getInt8(42);
+  EXPECT_FALSE(isSplatValue(ScalarC));
+
+  Constant *OtherScalarC = IRB.getInt8(-42);
+  Constant *NonSplatC = ConstantVector::get({ScalarC, OtherScalarC});
+  EXPECT_FALSE(isSplatValue(NonSplatC));
+
+  Value *SplatC = IRB.CreateVectorSplat(5, ScalarC);
+  EXPECT_TRUE(isSplatValue(SplatC));
+
+  // FIXME: Constant splat analysis does not allow undef elements.
+  Constant *SplatWithUndefC = ConstantVector::get({ScalarC, UndefScalar});
+  EXPECT_FALSE(isSplatValue(SplatWithUndefC));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_00) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %A = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> zeroinitializer\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_11) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %A = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_01) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %A = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 0, i32 1>\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+// FIXME: Constant (mask) splat analysis does not allow undef elements.
+
+TEST_F(VectorUtilsTest, isSplatValue_0u) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %A = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 0, i32 undef>\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Binop) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %v0 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 0, i32 0>\n"
+      "  %v1 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = udiv <2 x i8> %v0, %v1\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Binop_ConstantOp0) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %v1 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = ashr <2 x i8> <i8 42, i8 42>, %v1\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Binop_Not_Op0) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %v0 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 1, i32 0>\n"
+      "  %v1 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = add <2 x i8> %v0, %v1\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Binop_Not_Op1) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i8> %x) {\n"
+      "  %v0 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %v1 = shufflevector <2 x i8> %x, <2 x i8> undef, <2 x i32> <i32 0, i32 1>\n"
+      "  %A = shl <2 x i8> %v0, %v1\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Select) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i1> %x, <2 x i8> %y, <2 x i8> %z) {\n"
+      "  %v0 = shufflevector <2 x i1> %x, <2 x i1> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %v1 = shufflevector <2 x i8> %y, <2 x i8> undef, <2 x i32> <i32 0, i32 0>\n"
+      "  %v2 = shufflevector <2 x i8> %z, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = select <2 x i1> %v0, <2 x i8> %v1, <2 x i8> %v2\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Select_ConstantOp) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i1> %x, <2 x i8> %y, <2 x i8> %z) {\n"
+      "  %v0 = shufflevector <2 x i1> %x, <2 x i1> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %v2 = shufflevector <2 x i8> %z, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = select <2 x i1> %v0, <2 x i8> <i8 42, i8 42>, <2 x i8> %v2\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Select_NotCond) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i1> %x, <2 x i8> %y, <2 x i8> %z) {\n"
+      "  %v1 = shufflevector <2 x i8> %y, <2 x i8> undef, <2 x i32> <i32 0, i32 0>\n"
+      "  %v2 = shufflevector <2 x i8> %z, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = select <2 x i1> %x, <2 x i8> %v1, <2 x i8> %v2\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Select_NotOp1) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i1> %x, <2 x i8> %y, <2 x i8> %z) {\n"
+      "  %v0 = shufflevector <2 x i1> %x, <2 x i1> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %v2 = shufflevector <2 x i8> %z, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %A = select <2 x i1> %v0, <2 x i8> %y, <2 x i8> %v2\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_Select_NotOp2) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i1> %x, <2 x i8> %y, <2 x i8> %z) {\n"
+      "  %v0 = shufflevector <2 x i1> %x, <2 x i1> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %v1 = shufflevector <2 x i8> %y, <2 x i8> undef, <2 x i32> <i32 0, i32 0>\n"
+      "  %A = select <2 x i1> %v0, <2 x i8> %v1, <2 x i8> %z\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_FALSE(isSplatValue(A));
+}
+
+TEST_F(VectorUtilsTest, isSplatValue_SelectBinop) {
+  parseAssembly(
+      "define <2 x i8> @test(<2 x i1> %x, <2 x i8> %y, <2 x i8> %z) {\n"
+      "  %v0 = shufflevector <2 x i1> %x, <2 x i1> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %v1 = shufflevector <2 x i8> %y, <2 x i8> undef, <2 x i32> <i32 0, i32 0>\n"
+      "  %v2 = shufflevector <2 x i8> %z, <2 x i8> undef, <2 x i32> <i32 1, i32 1>\n"
+      "  %bo = xor <2 x i8> %v1, %v2\n"
+      "  %A = select <2 x i1> %v0, <2 x i8> %bo, <2 x i8> %v2\n"
+      "  ret <2 x i8> %A\n"
+      "}\n");
+  EXPECT_TRUE(isSplatValue(A));
+}
+
 TEST_F(VectorUtilsTest, getSplatValueElt0) {
   parseAssembly(
       "define <2 x i8> @test(i8 %x) {\n"