[Clang][CodeGen] Add workaround for old glibc __PTR_ALIGN macro

Author: dtcxzyw

clang/lib/AST/Expr.cpp

@@ -2247,6 +2247,15 @@ bool BinaryOperator::isNullPointerArithmeticExtension(ASTContext &Ctx,
     return false;
   }
 
+  // Workaround for old glibc's __PTR_ALIGN macro
+  if (auto *Select = dyn_cast<ConditionalOperator>(PExp->IgnoreParenCasts())) {
+    // If the condition can be constant evaluated, we check the selected arm.
+    bool EvalResult;
+    if (!Select->getCond()->EvaluateAsBooleanCondition(EvalResult, Ctx))
+      return false;
+    PExp = EvalResult ? Select->getTrueExpr() : Select->getFalseExpr();
+  }
+
   // Check that the pointer is a nullptr.
   if (!PExp->IgnoreParenCasts()
           ->isNullPointerConstant(Ctx, Expr::NPC_ValueDependentIsNotNull))

clang/test/CodeGen/glibc_ptr_align.c

@@ -3,15 +3,15 @@
 
 // Make sure that we do not set inbounds flag if the base pointer may be a constant null.
 
-// CHECK-LABEL: define dso_local noalias ptr @glibc_ptr_align(
+// CHECK-LABEL: define dso_local ptr @glibc_ptr_align(
 // CHECK-SAME: ptr noundef readnone captures(none) [[BASE:%.*]], ptr noundef [[POINTER:%.*]], i64 noundef [[ALIGN_MASK:%.*]]) local_unnamed_addr #[[ATTR0:[0-9]+]] {
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[POINTER]] to i64
 // CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[ALIGN_MASK]], [[SUB_PTR_LHS_CAST]]
 // CHECK-NEXT:    [[NOT:%.*]] = xor i64 [[ALIGN_MASK]], -1
 // CHECK-NEXT:    [[AND:%.*]] = and i64 [[ADD]], [[NOT]]
-// CHECK-NEXT:    [[ADD_PTR:%.*]] = getelementptr inbounds i8, ptr null, i64 [[AND]]
-// CHECK-NEXT:    ret ptr [[ADD_PTR]]
+// CHECK-NEXT:    [[TMP0:%.*]] = inttoptr i64 [[AND]] to ptr
+// CHECK-NEXT:    ret ptr [[TMP0]]
 //
 char *glibc_ptr_align(char *base, char *pointer, long align_mask) {
   return (sizeof(long int) < sizeof(void *) ? (base) : (char *)0) +
@@ -21,15 +21,15 @@ char *glibc_ptr_align(char *base, char *pointer, long align_mask) {
           ~(align_mask));
 }
 
-// CHECK-LABEL: define dso_local noalias ptr @glibc_ptr_align_commuted(
+// CHECK-LABEL: define dso_local ptr @glibc_ptr_align_commuted(
 // CHECK-SAME: ptr noundef readnone captures(none) [[BASE:%.*]], ptr noundef [[POINTER:%.*]], i64 noundef [[ALIGN_MASK:%.*]]) local_unnamed_addr #[[ATTR0]] {
 // CHECK-NEXT:  [[ENTRY:.*:]]
 // CHECK-NEXT:    [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[POINTER]] to i64
 // CHECK-NEXT:    [[ADD:%.*]] = add nsw i64 [[ALIGN_MASK]], [[SUB_PTR_LHS_CAST]]
 // CHECK-NEXT:    [[NOT:%.*]] = xor i64 [[ALIGN_MASK]], -1
 // CHECK-NEXT:    [[AND:%.*]] = and i64 [[ADD]], [[NOT]]
-// CHECK-NEXT:    [[ADD_PTR:%.*]] = getelementptr inbounds i8, ptr null, i64 [[AND]]
-// CHECK-NEXT:    ret ptr [[ADD_PTR]]
+// CHECK-NEXT:    [[TMP0:%.*]] = inttoptr i64 [[AND]] to ptr
+// CHECK-NEXT:    ret ptr [[TMP0]]
 //
 char *glibc_ptr_align_commuted(char *base, char *pointer, long align_mask) {
   return (sizeof(long int) >= sizeof(void *) ? (char *)0 : (base)) +