[PATCH] D140418: [APSInt] Fix bug in APSInt in issue 59513

[Peter Rong via Phabricator via llvm-commits]

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Also provide a tryExtValue() API like APInt did in D139683 <https://reviews.llvm.org/D139683>
Fix a use case in MIParser that used APSInt wrong and was revealed because of this patch.
This patch is almost identical to D140059 <https://reviews.llvm.org/D140059>, that one got reverted due to the previous MIParser use case.

getExtValue() used to provide a 64bit representation regardless of the sign.
After this patch, only 63 bits are allowed for unsigned value since the return value is int64_t.
This change of semantics caused some unit testing w/ large constants to fail.

We modify MIParser to refelect the intended behavior using `try` API introduced in D139683 <https://reviews.llvm.org/D139683>.
It's also a show case how `try` API can be used conveniently where user don't need to worry about
the detailed condition.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D140418

Files:
  llvm/include/llvm/ADT/APSInt.h
  llvm/lib/CodeGen/MIRParser/MIParser.cpp
  llvm/unittests/ADT/APSIntTest.cpp


Index: llvm/unittests/ADT/APSIntTest.cpp
===================================================================
--- llvm/unittests/ADT/APSIntTest.cpp
+++ llvm/unittests/ADT/APSIntTest.cpp
@@ -62,6 +62,13 @@
   EXPECT_EQ(UINT64_C(0) - 7, APSInt::getUnsigned(-7).getZExtValue());
 }
 
+TEST(APSIntTest, isRepresentableByInt64) {
+  ASSERT_TRUE(APSInt(APInt(3, 7), true).isRepresentableByInt64());
+  ASSERT_TRUE(APSInt(APInt(128, 7), true).isRepresentableByInt64());
+  ASSERT_TRUE(APSInt(APInt(128, 7), false).isRepresentableByInt64());
+  ASSERT_TRUE(APSInt(APInt(64, -1), false).isRepresentableByInt64());
+  ASSERT_FALSE(APSInt(APInt(64, (uint64_t)-1), true).isRepresentableByInt64());
+}
 TEST(APSIntTest, getExtValue) {
   EXPECT_TRUE(APSInt(APInt(3, 7), true).isUnsigned());
   EXPECT_TRUE(APSInt(APInt(3, 7), false).isSigned());
@@ -76,6 +83,16 @@
   EXPECT_EQ(9, APSInt(APInt(4, -7), true).getExtValue());
   EXPECT_EQ(-7, APSInt(APInt(4, -7), false).getExtValue());
 }
+TEST(APSIntTest, tryExtValue) {
+  ASSERT_EQ(-7, APSInt(APInt(64, -7), false).tryExtValue().value_or(42));
+  ASSERT_EQ(42, APSInt(APInt(128, -7), false).tryExtValue().value_or(42));
+  ASSERT_EQ(-1,
+            APSInt(APInt::getAllOnes(128), false).tryExtValue().value_or(42));
+  ASSERT_EQ(42, APSInt(APInt(64, -7), true).tryExtValue().value_or(42));
+  ASSERT_EQ(1, APSInt(APInt(128, 1), true).tryExtValue().value_or(42));
+  ASSERT_EQ(42,
+            APSInt(APInt::getAllOnes(128), true).tryExtValue().value_or(42));
+}
 
 TEST(APSIntTest, compareValues) {
   auto U = [](uint64_t V) { return APSInt::getUnsigned(V); };
Index: llvm/lib/CodeGen/MIRParser/MIParser.cpp
===================================================================
--- llvm/lib/CodeGen/MIRParser/MIParser.cpp
+++ llvm/lib/CodeGen/MIRParser/MIParser.cpp
@@ -1778,9 +1778,12 @@
 bool MIParser::parseImmediateOperand(MachineOperand &Dest) {
   assert(Token.is(MIToken::IntegerLiteral));
   const APSInt &Int = Token.integerValue();
-  if (Int.getMinSignedBits() > 64)
+  if (auto SImm = Int.trySExtValue(); Int.isSigned() && SImm.has_value())
+    Dest = MachineOperand::CreateImm(*SImm);
+  else if (auto UImm = Int.tryZExtValue(); !Int.isSigned() && UImm.has_value())
+    Dest = MachineOperand::CreateImm(*UImm);
+  else
     return error("integer literal is too large to be an immediate operand");
-  Dest = MachineOperand::CreateImm(Int.getExtValue());
   lex();
   return false;
 }
Index: llvm/include/llvm/ADT/APSInt.h
===================================================================
--- llvm/include/llvm/ADT/APSInt.h
+++ llvm/include/llvm/ADT/APSInt.h
@@ -85,12 +85,26 @@
   }
   using APInt::toString;
 
+  /// If this int is representable using an int64_t.
+  bool isRepresentableByInt64() const {
+    // For unsigned values with 64 active bits, they technically fit into a
+    // int64_t, but the user may get negative numbers and has to manually cast
+    // them to unsigned. Let's not bet the user has the sanity to do that and
+    // not give them a vague value at the first place.
+    return isSigned() ? isSignedIntN(64) : isIntN(63);
+  }
+
   /// Get the correctly-extended \c int64_t value.
   int64_t getExtValue() const {
-    assert(getMinSignedBits() <= 64 && "Too many bits for int64_t");
+    assert(isRepresentableByInt64() && "Too many bits for int64_t");
     return isSigned() ? getSExtValue() : getZExtValue();
   }
 
+  std::optional<int64_t> tryExtValue() const {
+    return isRepresentableByInt64() ? std::optional<int64_t>(getExtValue())
+                                    : std::nullopt;
+  }
+
   APSInt trunc(uint32_t width) const {
     return APSInt(APInt::trunc(width), IsUnsigned);
   }


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