[SVE] Make Constant::getSplatValue work for scalable vector splats

[ctetreau]

Summary

Make Constant::getSplatValue recognize scalable vector splats of the
form created by ConstantVector::getSplat. Add unit test to verify that
C == ConstantVector::getSplat(C)->getSplatValue() for fixed width and
scalable vector splats

[ctetreau]

appease clang-tidy

[ctetreau]

ping?

[efriedma]

It looks like this affects a bunch of the pattern-matchers in PatternMatch.h; for example, m_APInt. Is that right?

llvm/lib/IR/Constants.cpp

1604

I don't see any reason the index here would be a ConstantInt, in general. (I mean, the result here would be pretty silly if it wasn't, but nothing is actually enforcing it.)

[ctetreau]

rebase

[ctetreau]

This comment was removed by ctetreau.

[ctetreau]

add regression test

[ctetreau]

address code review issues

[efriedma]

LGTM

[ctetreau]

fix test

[ro]

This patch broke ninja check-all on the Solaris buildbots, e.g. clang-solaris11-sparcv9:

[530/724] Building CXX object unittests/IR/CMakeFiles/IRTests.dir/ConstantsTest.cpp.o
FAILED: unittests/IR/CMakeFiles/IRTests.dir/ConstantsTest.cpp.o 
/opt/llvm-buildbot/bin/c++  -DGTEST_HAS_RTTI=0 -DGTEST_HAS_TR1_TUPLE=0 -DGTEST_LANG_CXX11=1 -D_DEBUG -D_FILE_OFFSET_BITS=64 -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -Iunittests/IR -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR -Iinclude -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/Support/Solaris -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/utils/unittest/googletest/include -I/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/utils/unittest/googlemock/include -fPIC -fvisibility-inlines-hidden -Werror=date-time -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wno-missing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wno-maybe-uninitialized -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wno-comment -fdiagnostics-color -ffunction-sections -fdata-sections -O3     -Wno-variadic-macros -fno-exceptions -fno-rtti -UNDEBUG -std=c++14 -MD -MT unittests/IR/CMakeFiles/IRTests.dir/ConstantsTest.cpp.o -MF unittests/IR/CMakeFiles/IRTests.dir/ConstantsTest.cpp.o.d -o unittests/IR/CMakeFiles/IRTests.dir/ConstantsTest.cpp.o -c /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR/ConstantsTest.cpp
In file included from /usr/include/sys/select.h:27:0,
                 from /usr/include/sys/types.h:665,
                 from /usr/include/sys/wait.h:12,
                 from /usr/include/stdlib.h:16,
                 from /opt/llvm-buildbot/include/c++/7.4.0/cstdlib:75,
                 from /opt/llvm-buildbot/include/c++/7.4.0/bits/stl_algo.h:59,
                 from /opt/llvm-buildbot/include/c++/7.4.0/algorithm:62,
                 from /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/Support/MathExtras.h:17,
                 from /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/ADT/APInt.h:19,
                 from /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/ADT/APFloat.h:19,
                 from /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/include/llvm/IR/Constants.h:23,
                 from /opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR/ConstantsTest.cpp:9:
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR/ConstantsTest.cpp: In member function ‘virtual void llvm::{anonymous}::ConstantsTest_GetSplatValueRoundTrip_Test::TestBody()’:
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR/ConstantsTest.cpp:649:18: error: expected unqualified-id before numeric constant
     ElementCount SEC = {Min, true};
                  ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR/ConstantsTest.cpp:652:29: error: unable to deduce ‘std::initializer_list<auto>&&’ from ‘{1, FEC}’
     for (auto EC : {SEC, FEC}) {
                             ^
/opt/llvm-buildbot/home/solaris11-sparcv9/clang-solaris11-sparcv9/llvm/llvm/unittests/IR/ConstantsTest.cpp:652:29: note:   deduced conf

<sys/time.h> has #define SEC 1

Please fix.

[ctetreau]

@ro That's unfortunate. I pushed D83415, I'll submit without review when my local tests pass.

llvm/lib/IR/Constants.cpp

 Constant *Constant::getSplatValue(bool AllowUndefs) const {
   assert(this->getType()->isVectorTy() && "Only valid for vectors!");
   if (isa<ConstantAggregateZero>(this))
     return getNullValue(cast<VectorType>(getType())->getElementType());
   if (const ConstantDataVector *CV = dyn_cast<ConstantDataVector>(this))
     return CV->getSplatValue();
   if (const ConstantVector *CV = dyn_cast<ConstantVector>(this))
     return CV->getSplatValue(AllowUndefs);
+
+  // Check if this is a constant expression splat of the form returned by
+  // ConstantVector::getSplat()
+  const auto *Shuf = dyn_cast<ConstantExpr>(this);
+  if (Shuf && Shuf->getOpcode() == Instruction::ShuffleVector &&
+      isa<UndefValue>(Shuf->getOperand(1))) {
+
+    const auto *IElt = dyn_cast<ConstantExpr>(Shuf->getOperand(0));
+    if (IElt && IElt->getOpcode() == Instruction::InsertElement &&
+        isa<UndefValue>(IElt->getOperand(0))) {
+
+      ArrayRef<int> Mask = Shuf->getShuffleMask();
+      Constant *SplatVal = IElt->getOperand(1);
+      ConstantInt *Index = cast<ConstantInt>(IElt->getOperand(2));
+
+      if (Index->getValue() == 0 &&
+          std::all_of(Mask.begin(), Mask.end(), [](int I) { return I == 0; }))
+        return SplatVal;
+    }
+  }
+
   return nullptr;
 }
 
 Constant *ConstantVector::getSplatValue(bool AllowUndefs) const {
   // Check out first element.
   Constant *Elt = getOperand(0);
   // Then make sure all remaining elements point to the same value.
   for (unsigned I = 1, E = getNumOperands(); I < E; ++I) {

llvm/test/Transforms/InstSimplify/vscale.ll

 ; CHECK-LABEL: @insert_extract_element_same_vec_idx_2(
 ; CHECK-NEXT:    ret i32 1
 ;
   %v = insertelement <vscale x 4 x i32> undef, i32 1, i64 4
   %r = extractelement <vscale x 4 x i32> %v, i64 4
   ret i32 %r
 }
 
+; more complicated expressions
+
+define <vscale x 2 x i1> @cmp_le_smax_always_true(<vscale x 2 x i64> %x) {
+; CHECK_LABEL: @cmp_le_smax_always_true(
+; CHECK-NEXT:    ret <vscale x 2 x i1> shufflevector (<vscale x 2 x i1> insertelement (<vscale x 2 x i1> undef, i1 true, i32 0), <vscale x 2 x i1> undef, <vscale x 2 x i32> zeroinitializer)
+   %cmp = icmp sle <vscale x 2 x i64> %x, shufflevector (<vscale x 2 x i64> insertelement (<vscale x 2 x i64> undef, i64 9223372036854775807, i32 0), <vscale x 2 x i64> undef, <vscale x 2 x i32> zeroinitializer)
+   ret <vscale x 2 x i1> %cmp
+}
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Memory Access and Addressing Operations
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 
 ; getelementptr
 
 define <vscale x 4 x i32*> @getelementptr_constant_foldable_1() {
 ; CHECK-LABEL: @getelementptr_constant_foldable_1(

llvm/unittests/IR/ConstantsTest.cpp

TEST(ConstantsTest, isElementWiseEqual) {
   Constant *CP00U = ConstantVector::get({CP0, CP0, CPU});
 
   EXPECT_FALSE(CP0000->isElementWiseEqual(CP00U0));
   EXPECT_FALSE(CP00U0->isElementWiseEqual(CP0000));
   EXPECT_FALSE(CP0000->isElementWiseEqual(CP00U));
   EXPECT_FALSE(CP00U->isElementWiseEqual(CP00U0));
 }
 
+TEST(ConstantsTest, GetSplatValueRoundTrip) {
+  LLVMContext Context;
+
+  Type *FloatTy = Type::getFloatTy(Context);
+  Type *Int32Ty = Type::getInt32Ty(Context);
+  Type *Int8Ty = Type::getInt8Ty(Context);
+
+  for (unsigned Min : {1, 2, 8}) {
+    ElementCount SEC = {Min, true};
+    ElementCount FEC = {Min, false};
+
+    for (auto EC : {SEC, FEC}) {
+      for (auto *Ty : {FloatTy, Int32Ty, Int8Ty}) {
+        Constant *Zero = Constant::getNullValue(Ty);
+        Constant *One = Constant::getAllOnesValue(Ty);
+
+        for (auto *C : {Zero, One}) {
+          Constant *Splat = ConstantVector::getSplat(EC, C);
+          ASSERT_NE(nullptr, Splat);
+
+          Constant *SplatVal = Splat->getSplatValue();
+          EXPECT_NE(nullptr, SplatVal);
+          EXPECT_EQ(SplatVal, C);
+        }
+      }
+    }
+  }
+}
+
 }  // end anonymous namespace
 }  // end namespace llvm