[clang] Revert "[Sema] Add check for bitfield assignments to integral types" (PR #68963)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: None (vabridgers)

<details>
<summary>Changes</summary>

This reverts commit 47e36266e93de9c34ba3028951a58124864bb2b4.

This change broke some arm8/arm7 build bots because int and void * have the same size.

---
Full diff: https://github.com/llvm/llvm-project/pull/68963.diff


5 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (-3) 
- (modified) clang/include/clang/Basic/DiagnosticGroups.td (-2) 
- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (-3) 
- (modified) clang/lib/Sema/SemaChecking.cpp (+1-12) 
- (removed) clang/test/SemaCXX/bitfield-width.c (-34) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 31969201a1cac8c..2d918967e7f0b02 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -185,9 +185,6 @@ New Compiler Flags
   the preprocessed text to the output. This can greatly reduce the size of the
   preprocessed output, which can be helpful when trying to reduce a test case.
 
-* ``-Wbitfield-conversion`` was added to detect assignments of integral
-  types to a bitfield that may change the value.
-
 Deprecated Compiler Flags
 -------------------------
 
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 674eb9f4ef2e73f..0b09c002191848a 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -53,7 +53,6 @@ def SingleBitBitFieldConstantConversion :
 def BitFieldConstantConversion : DiagGroup<"bitfield-constant-conversion",
                                            [SingleBitBitFieldConstantConversion]>;
 def BitFieldEnumConversion : DiagGroup<"bitfield-enum-conversion">;
-def BitFieldConversion : DiagGroup<"bitfield-conversion">;
 def BitFieldWidth : DiagGroup<"bitfield-width">;
 def CompoundTokenSplitByMacro : DiagGroup<"compound-token-split-by-macro">;
 def CompoundTokenSplitBySpace : DiagGroup<"compound-token-split-by-space">;
@@ -934,7 +933,6 @@ def Conversion : DiagGroup<"conversion",
                             ConstantConversion,
                             EnumConversion,
                             BitFieldEnumConversion,
-                            BitFieldConversion,
                             FloatConversion,
                             Shorten64To32,
                             IntConversion,
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index ab7fe881976aad2..c1a6e3831127e56 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6171,9 +6171,6 @@ def warn_signed_bitfield_enum_conversion : Warning<
   "signed bit-field %0 needs an extra bit to represent the largest positive "
   "enumerators of %1">,
   InGroup<BitFieldEnumConversion>, DefaultIgnore;
-def warn_bitfield_too_small_for_integral_type : Warning<
-  "conversion from %2 (%3 bits) to bit-field %0 (%1 bits) may change value">,
-  InGroup<BitFieldConversion>, DefaultIgnore;
 def note_change_bitfield_sign : Note<
   "consider making the bitfield type %select{unsigned|signed}0">;
 
diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index cd61459cfbb13d6..35b36db2049db09 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -14298,18 +14298,6 @@ static bool AnalyzeBitFieldAssignment(Sema &S, FieldDecl *Bitfield, Expr *Init,
         S.Diag(WidthExpr->getExprLoc(), diag::note_widen_bitfield)
             << BitsNeeded << ED << WidthExpr->getSourceRange();
       }
-    } else if (OriginalInit->getType()->isIntegralType(S.Context)) {
-      IntRange LikelySourceRange =
-          GetExprRange(S.Context, Init, S.isConstantEvaluatedContext(),
-                       /*Approximate=*/true);
-
-      if (LikelySourceRange.Width > FieldWidth) {
-        Expr *WidthExpr = Bitfield->getBitWidth();
-        S.Diag(InitLoc, diag::warn_bitfield_too_small_for_integral_type)
-            << Bitfield << FieldWidth << OriginalInit->getType()
-            << LikelySourceRange.Width;
-        S.Diag(WidthExpr->getExprLoc(), diag::note_declared_at);
-      }
     }
 
     return false;
@@ -15207,6 +15195,7 @@ static void CheckImplicitConversion(Sema &S, Expr *E, QualType T,
 
   if (LikelySourceRange.Width > TargetRange.Width) {
     // If the source is a constant, use a default-on diagnostic.
+    // TODO: this should happen for bitfield stores, too.
     Expr::EvalResult Result;
     if (E->EvaluateAsInt(Result, S.Context, Expr::SE_AllowSideEffects,
                          S.isConstantEvaluatedContext())) {
diff --git a/clang/test/SemaCXX/bitfield-width.c b/clang/test/SemaCXX/bitfield-width.c
deleted file mode 100644
index 8219054b959e544..000000000000000
--- a/clang/test/SemaCXX/bitfield-width.c
+++ /dev/null
@@ -1,34 +0,0 @@
-// RUN: %clang_cc1 -Wconversion -fsyntax-only -verify %s
-// RUN: %clang_cc1 -Wbitfield-conversion -fsyntax-only -verify %s
-
-typedef struct _xx {
-     int bf:9; // expected-note 4{{declared here}}
- } xx, *pxx; 
-
- xx vxx;
-
- void foo1(int x) {     
-     vxx.bf = x; // expected-warning{{conversion from 'int' (32 bits) to bit-field 'bf' (9 bits) may change value}}
- } 
- void foo2(short x) {     
-     vxx.bf = x; // expected-warning{{conversion from 'short' (16 bits) to bit-field 'bf' (9 bits) may change value}}
- } 
- void foo3(char x) {     
-     vxx.bf = x; // no warning expected
- } 
- void foo5(void * x) {     
-     vxx.bf = (int)x; // expected-warning{{cast to smaller integer type 'int' from 'void *'}}
-     // expected-warning at -1{{conversion from 'int' (32 bits) to bit-field 'bf' (9 bits) may change value}}
- } 
- void foo6(short x) {     
-     vxx.bf = 0xff & x; // no warning expected 
- } 
- void foo7(short x) {     
-     vxx.bf = 0x1ff & x; // no warning expected 
- } 
- void foo8(short x) {     
-     vxx.bf = 0x3ff & x; // expected-warning{{conversion from 'int' (10 bits) to bit-field 'bf' (9 bits) may change value}}
- } 
- int fee(void) {
-     return 0;
- }

``````````

</details>


https://github.com/llvm/llvm-project/pull/68963