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[Analysis] add isSplatValue() for vectors in IR

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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
This commit is contained in:
Sanjay Patel 2019-06-11 22:25:18 +00:00
parent 0ea02e1312
commit 9db50a3254
3 changed files with 235 additions and 0 deletions
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6
include/llvm/Analysis/VectorUtils.h
View File

@ -78,6 +78,12 @@ Value *findScalarElement(Value *V, unsigned EltNo);
/// a sequence of instructions that broadcast a single value into a vector.
const Value *getSplatValue(const Value *V);
/// Return true if the input value is known to be a vector with all identical
/// elements (potentially including undefined elements).
/// This may be more powerful than the related getSplatValue() because it is
/// not limited by finding a scalar source value to a splatted vector.
bool isSplatValue(const Value *V, unsigned Depth = 0);
/// Compute a map of integer instructions to their minimum legal type
/// size.
///

39
lib/Analysis/VectorUtils.cpp
View File

@ -321,6 +321,45 @@ const llvm::Value *llvm::getSplatValue(const Value *V) {
return nullptr;
}
// This setting is based on its counterpart in value tracking, but it could be
// adjusted if needed.
const unsigned MaxDepth = 6;
bool llvm::isSplatValue(const Value *V, unsigned Depth) {
assert(Depth <= MaxDepth && "Limit Search Depth");
if (isa<VectorType>(V->getType())) {
if (isa<UndefValue>(V))
return true;
// FIXME: Constant splat analysis does not allow undef elements.
if (auto *C = dyn_cast<Constant>(V))
return C->getSplatValue() != nullptr;
}
// FIXME: Constant splat analysis does not allow undef elements.
Constant *Mask;
if (match(V, m_ShuffleVector(m_Value(), m_Value(), m_Constant(Mask))))
return Mask->getSplatValue() != nullptr;
// The remaining tests are all recursive, so bail out if we hit the limit.
if (Depth++ == MaxDepth)
return false;
// If both operands of a binop are splats, the result is a splat.
Value *X, *Y, *Z;
if (match(V, m_BinOp(m_Value(X), m_Value(Y))))
return isSplatValue(X, Depth) && isSplatValue(Y, Depth);
// If all operands of a select are splats, the result is a splat.
if (match(V, m_Select(m_Value(X), m_Value(Y), m_Value(Z))))
return isSplatValue(X, Depth) && isSplatValue(Y, Depth) &&
isSplatValue(Z, Depth);
// TODO: Add support for unary ops (fneg), casts, intrinsics (overflow ops).
return false;
}
MapVector<Instruction *, uint64_t>
llvm::computeMinimumValueSizes(ArrayRef<BasicBlock *> Blocks, DemandedBits &DB,
const TargetTransformInfo *TTI) {

190
unittests/Analysis/VectorUtilsTest.cpp
View File

@ -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"