[PATCH] D63691: [APInt] Fix getBitsNeeded for INT_MIN values

[Dmitry Venikov via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL364710: [APInt] Fix getBitsNeeded for INT_MIN values (authored by Quolyk, committed by ).

Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D63691/new/

https://reviews.llvm.org/D63691

Files:
  llvm/trunk/lib/Support/APInt.cpp
  llvm/trunk/unittests/ADT/APIntTest.cpp


Index: llvm/trunk/unittests/ADT/APIntTest.cpp
===================================================================
--- llvm/trunk/unittests/ADT/APIntTest.cpp
+++ llvm/trunk/unittests/ADT/APIntTest.cpp
@@ -1263,8 +1263,21 @@
   EXPECT_EQ(6U, APInt::getBitsNeeded("-19", 10));
   EXPECT_EQ(6U, APInt::getBitsNeeded("-20", 10));
 
-  // TODO: INT_MIN cases need 1 less bit (PR40897)
-  EXPECT_EQ(9U, APInt::getBitsNeeded("-128", 10));
+  EXPECT_EQ(1U, APInt::getBitsNeeded("-1", 10));
+  EXPECT_EQ(2U, APInt::getBitsNeeded("-2", 10));
+  EXPECT_EQ(3U, APInt::getBitsNeeded("-4", 10));
+  EXPECT_EQ(4U, APInt::getBitsNeeded("-8", 10));
+  EXPECT_EQ(5U, APInt::getBitsNeeded("-16", 10));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("-23", 10));
+  EXPECT_EQ(6U, APInt::getBitsNeeded("-32", 10));
+  EXPECT_EQ(7U, APInt::getBitsNeeded("-64", 10));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("-127", 10));
+  EXPECT_EQ(8U, APInt::getBitsNeeded("-128", 10));
+  EXPECT_EQ(9U, APInt::getBitsNeeded("-255", 10));
+  EXPECT_EQ(9U, APInt::getBitsNeeded("-256", 10));
+  EXPECT_EQ(10U, APInt::getBitsNeeded("-512", 10));
+  EXPECT_EQ(11U, APInt::getBitsNeeded("-1024", 10));
+  EXPECT_EQ(12U, APInt::getBitsNeeded("-1025", 10));
 }
 
 TEST(APIntTest, StringBitsNeeded16) {
Index: llvm/trunk/lib/Support/APInt.cpp
===================================================================
--- llvm/trunk/lib/Support/APInt.cpp
+++ llvm/trunk/lib/Support/APInt.cpp
@@ -482,10 +482,13 @@
   APInt tmp(sufficient, StringRef(p, slen), radix);
 
   // Compute how many bits are required. If the log is infinite, assume we need
-  // just bit.
+  // just bit. If the log is exact and value is negative, then the value is
+  // MinSignedValue with (log + 1) bits.
   unsigned log = tmp.logBase2();
   if (log == (unsigned)-1) {
     return isNegative + 1;
+  } else if (isNegative && tmp.isPowerOf2()) {
+    return isNegative + log;
   } else {
     return isNegative + log + 1;
   }


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