[GlobalISel] Add convenience matchers for nots and all-ones constants

Add a convenience matcher which handles

```
G_XOR %not_reg, -1
```

And a convenience matcher which returns true if an integer constant is
all-ones.

Differential Revision: https://reviews.llvm.org/D91459

Author: Jessica Paquette

llvm/include/llvm/CodeGen/GlobalISel/MIPatternMatch.h

@@ -68,8 +68,13 @@ inline SpecificConstantMatch m_SpecificICst(int64_t RequestedValue) {
   return SpecificConstantMatch(RequestedValue);
 }
 
-/// Matches an integer 0.
+///{
+/// Convenience matchers for specific integer values.
 inline SpecificConstantMatch m_ZeroInt() { return SpecificConstantMatch(0); }
+inline SpecificConstantMatch m_AllOnesInt() {
+  return SpecificConstantMatch(-1);
+}
+///}
 
 // TODO: Rework this for different kinds of MachineOperand.
 // Currently assumes the Src for a match is a register.
@@ -451,6 +456,14 @@ m_Neg(const SrcTy &&Src) {
   return m_GSub(m_ZeroInt(), Src);
 }
 
+/// Matches a register not-ed by a G_XOR.
+/// G_XOR %not_reg, -1
+template <typename SrcTy>
+inline BinaryOp_match<SrcTy, SpecificConstantMatch, TargetOpcode::G_XOR, true>
+m_Not(const SrcTy &&Src) {
+  return m_GXor(Src, m_AllOnesInt());
+}
+
 } // namespace GMIPatternMatch
 } // namespace llvm
 

llvm/unittests/CodeGen/GlobalISel/PatternMatchTest.cpp

@@ -426,6 +426,17 @@ TEST_F(AArch64GISelMITest, MatchZeroInt) {
   EXPECT_FALSE(mi_match(FortyTwo.getReg(0), *MRI, m_ZeroInt()));
 }
 
+TEST_F(AArch64GISelMITest, MatchAllOnesInt) {
+  setUp();
+  if (!TM)
+    return;
+  auto AllOnes = B.buildConstant(LLT::scalar(64), -1);
+  EXPECT_TRUE(mi_match(AllOnes.getReg(0), *MRI, m_AllOnesInt()));
+
+  auto FortyTwo = B.buildConstant(LLT::scalar(64), 42);
+  EXPECT_FALSE(mi_match(FortyTwo.getReg(0), *MRI, m_AllOnesInt()));
+}
+
 TEST_F(AArch64GISelMITest, MatchNeg) {
   setUp();
   if (!TM)
@@ -457,6 +468,39 @@ TEST_F(AArch64GISelMITest, MatchNeg) {
   EXPECT_TRUE(mi_match(AddInst.getReg(2), *MRI, m_Neg(m_Reg(NegatedReg))));
   EXPECT_EQ(NegatedReg, Copies[0]);
 }
+
+TEST_F(AArch64GISelMITest, MatchNot) {
+  setUp();
+  if (!TM)
+    return;
+
+  LLT s64 = LLT::scalar(64);
+  auto AllOnes = B.buildConstant(LLT::scalar(64), -1);
+  auto NotInst1 = B.buildXor(s64, Copies[0], AllOnes);
+  Register NotReg;
+
+  // Match: G_XOR %NotReg, -1
+  EXPECT_TRUE(mi_match(NotInst1.getReg(0), *MRI, m_Not(m_Reg(NotReg))));
+  EXPECT_EQ(NotReg, Copies[0]);
+
+  // Match: G_XOR -1, %NotReg
+  auto NotInst2 = B.buildXor(s64, AllOnes, Copies[1]);
+  EXPECT_TRUE(mi_match(NotInst2.getReg(0), *MRI, m_Not(m_Reg(NotReg))));
+  EXPECT_EQ(NotReg, Copies[1]);
+
+  // Don't match: G_XOR %NotReg, 42
+  auto FortyTwo = B.buildConstant(LLT::scalar(64), 42);
+  auto WrongCst = B.buildXor(s64, Copies[0], FortyTwo);
+  EXPECT_FALSE(mi_match(WrongCst.getReg(0), *MRI, m_Not(m_Reg(NotReg))));
+
+  // Complex testcase.
+  // %xor = G_XOR %NotReg, -1
+  // %add = G_ADD %x, %xor
+  auto AddInst = B.buildAdd(s64, Copies[1], NotInst1);
+  NotReg = Register();
+  EXPECT_TRUE(mi_match(AddInst.getReg(2), *MRI, m_Not(m_Reg(NotReg))));
+  EXPECT_EQ(NotReg, Copies[0]);
+}
 } // namespace
 
 int main(int argc, char **argv) {