[GlobalIsel] [Utility] [NFC] Added isConstantOrConstantSplatVectorFP to handle float constants.

llvm/include/llvm/CodeGen/GlobalISel/Utils.h

@@ -522,6 +522,13 @@ std::optional<APInt>
 isConstantOrConstantSplatVector(MachineInstr &MI,
                                 const MachineRegisterInfo &MRI);
 
+/// Determines if \p MI defines a float constant integer or a splat vector of
+/// float constant integers.
+/// \returns the float constant or std::nullopt.
+std::optional<APFloat>
+isConstantOrConstantSplatVectorFP(MachineInstr &MI,
+                                  const MachineRegisterInfo &MRI);
+
 /// Attempt to match a unary predicate against a scalar/splat constant or every
 /// element of a constant G_BUILD_VECTOR. If \p ConstVal is null, the source
 /// value was undef.

llvm/lib/CodeGen/GlobalISel/Utils.cpp

@@ -1517,6 +1517,18 @@ llvm::isConstantOrConstantSplatVector(MachineInstr &MI,
   return APInt(ScalarSize, *MaybeCst, true);
 }
 
+std::optional<APFloat>
+llvm::isConstantOrConstantSplatVectorFP(MachineInstr &MI,
+                                        const MachineRegisterInfo &MRI) {
+  Register Def = MI.getOperand(0).getReg();
+  if (auto FpConst = getFConstantVRegValWithLookThrough(Def, MRI))
+    return FpConst->Value;
+  auto MaybeCstFP = getFConstantSplat(Def, MRI, /*allowUndef=*/false);
+  if (!MaybeCstFP)
+    return std::nullopt;
+  return MaybeCstFP->Value;
+}
+
 bool llvm::isNullOrNullSplat(const MachineInstr &MI,
                              const MachineRegisterInfo &MRI, bool AllowUndefs) {
   switch (MI.getOpcode()) {

llvm/unittests/CodeGen/GlobalISel/GISelUtilsTest.cpp

@@ -77,6 +77,15 @@ static const LLT NXV3P0 = LLT::scalable_vector(3, P0);
 static const LLT NXV4P0 = LLT::scalable_vector(4, P0);
 static const LLT NXV12P0 = LLT::scalable_vector(12, P0);
 
+static void collectNonCopyMI(SmallVectorImpl<MachineInstr *> &MIList,
+                             MachineFunction *MF) {
+  for (auto &MBB : *MF)
+    for (MachineInstr &MI : MBB) {
+      if (MI.getOpcode() != TargetOpcode::COPY)
+        MIList.push_back(&MI);
+    }
+}
+
 TEST(GISelUtilsTest, getGCDType) {
   EXPECT_EQ(S1, getGCDType(S1, S1));
   EXPECT_EQ(S32, getGCDType(S32, S32));
@@ -408,4 +417,72 @@ TEST_F(AArch64GISelMITest, ConstFalseTest) {
     }
   }
 }
+
+TEST_F(AMDGPUGISelMITest, isConstantOrConstantSplatVectorFP) {
+  StringRef MIRString =
+      "  %cst0:_(s32) = G_FCONSTANT float 2.000000e+00\n"
+      "  %cst1:_(s32) = G_FCONSTANT float 0.0\n"
+      "  %cst2:_(s64) = G_FCONSTANT double 3.000000e-02\n"
+      "  %cst3:_(s32) = G_CONSTANT i32 2\n"
+      "  %cst4:_(<2 x s32>) = G_BUILD_VECTOR %cst0(s32), %cst0(s32)\n"
+      "  %cst5:_(<2 x s32>) = G_BUILD_VECTOR %cst1(s32), %cst0(s32)\n"
+      "  %cst6:_(<2 x s64>) = G_BUILD_VECTOR %cst2(s64), %cst2(s64)\n"
+      "  %cst7:_(<2 x s32>) = G_BUILD_VECTOR %cst3(s32), %cst3:_(s32)\n"
+      "  %cst8:_(<4 x s32>) = G_CONCAT_VECTORS %cst4:_(<2 x s32>), %cst4:_(<2 "
+      "x s32>)\n"
+      "  %cst9:_(<4 x s64>) = G_CONCAT_VECTORS %cst6:_(<2 x s64>), %cst6:_(<2 "
+      "x s64>)\n"
+      "  %cst10:_(<4 x s32>) = G_CONCAT_VECTORS %cst4:_(<2 x s32>), %cst5:_(<2 "
+      "x s32>)\n"
+      "  %cst11:_(<4 x s32>) = G_CONCAT_VECTORS %cst7:_(<2 x s32>), %cst7:_(<2 "
+      "x s32>)\n";
+
+  SmallVector<MachineInstr *, 16> MIList;
+
+  setUp(MIRString);
+  if (!TM)
+    GTEST_SKIP();
+
+  collectNonCopyMI(MIList, MF);
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[0], *MRI).has_value());
+  auto val = isConstantOrConstantSplatVectorFP(*MIList[0], *MRI).value();
+  EXPECT_EQ(2.0, val.convertToFloat());
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[1], *MRI).has_value());
+  val = isConstantOrConstantSplatVectorFP(*MIList[1], *MRI).value();
+  EXPECT_EQ(0.0, val.convertToFloat());
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[2], *MRI).has_value());
+  val = isConstantOrConstantSplatVectorFP(*MIList[2], *MRI).value();
+  EXPECT_EQ(0.03, val.convertToDouble());
+
+  EXPECT_FALSE(isConstantOrConstantSplatVectorFP(*MIList[3], *MRI).has_value());
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[4], *MRI).has_value());
+  val = isConstantOrConstantSplatVectorFP(*MIList[4], *MRI).value();
+  EXPECT_EQ(2.0, val.convertToFloat());
+
+  EXPECT_FALSE(isConstantOrConstantSplatVectorFP(*MIList[5], *MRI).has_value());
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[6], *MRI).has_value());
+  val = isConstantOrConstantSplatVectorFP(*MIList[6], *MRI).value();
+  EXPECT_EQ(0.03, val.convertToDouble());
+
+  EXPECT_FALSE(isConstantOrConstantSplatVectorFP(*MIList[7], *MRI).has_value());
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[8], *MRI).has_value());
+  val = isConstantOrConstantSplatVectorFP(*MIList[8], *MRI).value();
+  EXPECT_EQ(2.0, val.convertToFloat());
+
+  EXPECT_TRUE(isConstantOrConstantSplatVectorFP(*MIList[9], *MRI).has_value());
+  val = isConstantOrConstantSplatVectorFP(*MIList[9], *MRI).value();
+  EXPECT_EQ(0.03, val.convertToDouble());
+
+  EXPECT_FALSE(
+      isConstantOrConstantSplatVectorFP(*MIList[10], *MRI).has_value());
+
+  EXPECT_FALSE(
+      isConstantOrConstantSplatVectorFP(*MIList[11], *MRI).has_value());
+}
 }