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[Clang][CodeGen] Add workaround for old glibc __PTR_ALIGN macro (#137851)

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This patch adds a workaround for the old glibc `__PTR_ALIGN` macro:
```
((sizeof(long int) < sizeof(void *) ? (base) : (char *)0) +
   (((pointer) - (sizeof(long int) < sizeof(void *) ? (base) : (char *)0) +
     (align_mask)) &
    ~(align_mask)));
```
Closes https://github.com/llvm/llvm-project/issues/137833.
This commit is contained in:
Yingwei Zheng
2025-05-09 19:23:48 +08:00
committed by GitHub
parent 4923cffc1d
commit 61a8da9367
2 changed files with 72 additions and 0 deletions
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10
clang/lib/AST/Expr.cpp
View File

@@ -2247,6 +2247,16 @@ bool BinaryOperator::isNullPointerArithmeticExtension(ASTContext &Ctx,
return false;
}
// Workaround for old glibc's __PTR_ALIGN macro
if (auto *Select =
dyn_cast<ConditionalOperator>(PExp->IgnoreParenNoopCasts(Ctx))) {
// 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))

62
clang/test/CodeGen/glibc_ptr_align.c Normal file
View File

@@ -0,0 +1,62 @@
// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 5
// RUN: %clang_cc1 -triple=x86_64-unknown-unknown -O3 -o - -emit-llvm %s | FileCheck %s
// Make sure that we do not set inbounds flag if the base pointer may be a constant null.
// 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: [[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) +
(((pointer) -
(sizeof(long int) < sizeof(void *) ? (base) : (char *)0) +
(align_mask)) &
~(align_mask));
}
// 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: [[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)) +
(((pointer) -
(sizeof(long int) >= sizeof(void *) ? (char *)0 : (base)) +
(align_mask)) &
~(align_mask));
}
// CHECK-LABEL: define dso_local ptr @glibc_ptr_align_non_constexpr(
// CHECK-SAME: ptr noundef [[BASE:%.*]], ptr noundef [[POINTER:%.*]], i64 noundef [[ALIGN_MASK:%.*]], i32 noundef [[COND:%.*]]) local_unnamed_addr #[[ATTR0]] {
// CHECK-NEXT: [[ENTRY:.*:]]
// CHECK-NEXT: [[TOBOOL_NOT:%.*]] = icmp eq i32 [[COND]], 0
// CHECK-NEXT: [[COND1:%.*]] = select i1 [[TOBOOL_NOT]], ptr null, ptr [[BASE]]
// CHECK-NEXT: [[SUB_PTR_LHS_CAST:%.*]] = ptrtoint ptr [[POINTER]] to i64
// CHECK-NEXT: [[SUB_PTR_RHS_CAST:%.*]] = ptrtoint ptr [[COND1]] to i64
// CHECK-NEXT: [[SUB_PTR_SUB:%.*]] = add i64 [[ALIGN_MASK]], [[SUB_PTR_LHS_CAST]]
// CHECK-NEXT: [[ADD:%.*]] = sub i64 [[SUB_PTR_SUB]], [[SUB_PTR_RHS_CAST]]
// CHECK-NEXT: [[NOT:%.*]] = xor i64 [[ALIGN_MASK]], -1
// CHECK-NEXT: [[AND:%.*]] = and i64 [[ADD]], [[NOT]]
// CHECK-NEXT: [[ADD_PTR:%.*]] = getelementptr inbounds i8, ptr [[COND1]], i64 [[AND]]
// CHECK-NEXT: ret ptr [[ADD_PTR]]
//
char *glibc_ptr_align_non_constexpr(char *base, char *pointer, long align_mask, int cond) {
return (cond ? (base) : (char *)0) +
(((pointer) -
(cond ? (base) : (char *)0) +
(align_mask)) &
~(align_mask));
}