[clang] 5bbe153 - Cap IntRange::Width to MaxWidth (#145356)

[via cfe-commits]

Author: Akira Hatanaka
Date: 2025-06-26T08:03:32-07:00
New Revision: 5bbe1536dfa6f1dce8737e466c209c553d614e50

URL: https://github.com/llvm/llvm-project/commit/5bbe1536dfa6f1dce8737e466c209c553d614e50
DIFF: https://github.com/llvm/llvm-project/commit/5bbe1536dfa6f1dce8737e466c209c553d614e50.diff

LOG: Cap IntRange::Width to MaxWidth (#145356)

This commit addresses a fallout introduced by #126846.

Previously, TryGetExprRange would return an IntRange that has an active
range exceeding the maximum representable range for the expression's
underlying type. This led to clang erroneously issuing warnings about
implicit conversions losing integer precision.

This commit fixes the bug by capping IntRange::Width to MaxWidth.

rdar://149444029

Added: 
    

Modified: 
    clang/lib/Sema/SemaChecking.cpp
    clang/test/Sema/implicit-int-conversion-on-int.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 3407fd2d57d32..048b0892f6a31 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -10805,10 +10805,9 @@ static std::optional<IntRange> TryGetExprRange(ASTContext &C, const Expr *E,
         return std::nullopt;
 
       // If the range was previously non-negative, we need an extra bit for the
-      // sign bit. If the range was not non-negative, we need an extra bit
-      // because the negation of the most-negative value is one bit wider than
-      // that value.
-      return IntRange(SubRange->Width + 1, false);
+      // sign bit. Otherwise, we need an extra bit because the negation of the
+      // most-negative value is one bit wider than that value.
+      return IntRange(std::min(SubRange->Width + 1, MaxWidth), false);
     }
 
     case UO_Not: {
@@ -10825,7 +10824,9 @@ static std::optional<IntRange> TryGetExprRange(ASTContext &C, const Expr *E,
 
       // The width increments by 1 if the sub-expression cannot be negative
       // since it now can be.
-      return IntRange(SubRange->Width + (int)SubRange->NonNegative, false);
+      return IntRange(
+          std::min(SubRange->Width + (int)SubRange->NonNegative, MaxWidth),
+          false);
     }
 
     default:

diff  --git a/clang/test/Sema/implicit-int-conversion-on-int.c b/clang/test/Sema/implicit-int-conversion-on-int.c
index f555893d9e17a..3b1d81cd6a9ab 100644
--- a/clang/test/Sema/implicit-int-conversion-on-int.c
+++ b/clang/test/Sema/implicit-int-conversion-on-int.c
@@ -48,3 +48,11 @@ unsigned long long test_ull(unsigned long long x) {
 unsigned _BitInt(16) test_unsigned_bit_int(unsigned _BitInt(16) x) {
   return -x;
 }
+
+unsigned test_shift_minus(int i) {
+  return -(1 << i);
+}
+
+unsigned test_shift_not(int i) {
+  return ~(1 << i);
+}