https://github.com/dtcxzyw updated
https://github.com/llvm/llvm-project/pull/137851
>From f1db3a540ec1383451955efab62b64ed8d180349 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2...@gmail.com>
Date: Wed, 30 Apr 2025 01:26:41 +0800
Subject: [PATCH 1/4] [Clang][CodeGen] Check
`isUnderlyingBasePointerConstantNull` in `emitPointerArithmetic`
---
clang/lib/CodeGen/CGExprScalar.cpp | 3 ++-
.../test/CodeGen/catch-nullptr-and-nonzero-offset.c | 12 ++++++++++++
2 files changed, 14 insertions(+), 1 deletion(-)
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp
b/clang/lib/CodeGen/CGExprScalar.cpp
index 8dbbcdaef25d8..d214d2af52563 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -4238,7 +4238,8 @@ static Value *emitPointerArithmetic(CodeGenFunction &CGF,
else
elemTy = CGF.ConvertTypeForMem(elementType);
- if (CGF.getLangOpts().PointerOverflowDefined)
+ if (CGF.getLangOpts().PointerOverflowDefined ||
+ CGF.isUnderlyingBasePointerConstantNull(pointerOperand))
return CGF.Builder.CreateGEP(elemTy, pointer, index, "add.ptr");
return CGF.EmitCheckedInBoundsGEP(
diff --git a/clang/test/CodeGen/catch-nullptr-and-nonzero-offset.c
b/clang/test/CodeGen/catch-nullptr-and-nonzero-offset.c
index 63b6db2c2adeb..c5ae3f8bcc368 100644
--- a/clang/test/CodeGen/catch-nullptr-and-nonzero-offset.c
+++ b/clang/test/CodeGen/catch-nullptr-and-nonzero-offset.c
@@ -431,6 +431,18 @@ char *void_ptr(void *base, unsigned long offset) {
return base + offset;
}
+int *constant_null_add(long offset) {
+ // CHECK: define{{.*}} ptr @constant_null_add(i64 noundef %[[OFFSET:.*]])
+ // CHECK-NEXT: [[ENTRY:.*]]:
+ // CHECK-NEXT: %[[OFFSET_ADDR:.*]] = alloca i64, align 8
+ // CHECK-NEXT: store i64 %[[OFFSET]], ptr %[[OFFSET_ADDR]], align 8
+ // CHECK-NEXT: %[[OFFSET_RELOADED:.*]] = load i64, ptr %[[OFFSET_ADDR]],
align 8
+ // CHECK-NEXT: %[[ADD_PTR:.*]] = getelementptr i32, ptr null, i64
%[[OFFSET_RELOADED]]
+ // CHECK-NEXT: ret ptr %[[ADD_PTR]]
+#line 1800
+ return (int *)0 + offset;
+}
+
#ifdef __cplusplus
}
#endif
>From 630ce89088ef4978eafe884766712279a0d8fd56 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2...@gmail.com>
Date: Wed, 30 Apr 2025 01:47:45 +0800
Subject: [PATCH 2/4] [Clang][CodeGen] Add pre-commit tests. NFC.
---
clang/test/CodeGen/glibc_ptr_align.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
create mode 100644 clang/test/CodeGen/glibc_ptr_align.c
diff --git a/clang/test/CodeGen/glibc_ptr_align.c
b/clang/test/CodeGen/glibc_ptr_align.c
new file mode 100644
index 0000000000000..ebdb53cf7b53d
--- /dev/null
+++ b/clang/test/CodeGen/glibc_ptr_align.c
@@ -0,0 +1,17 @@
+// 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 noalias noundef ptr @glibc_ptr_align(
+// CHECK-SAME: ptr noundef readnone captures(none) [[BASE:%.*]], ptr noundef
readnone captures(none) [[POINTER:%.*]], i64 noundef [[ALIGN_MASK:%.*]])
local_unnamed_addr #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT: [[ENTRY:.*:]]
+// CHECK-NEXT: ret ptr null
+//
+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));
+}
>From ff88c23843d07a1c3142294a3d7c0894f0267a48 Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2...@gmail.com>
Date: Wed, 30 Apr 2025 01:49:10 +0800
Subject: [PATCH 3/4] [Clang][CodeGen] Add workaround for old glibc
`__PTR_ALIGN` macro
---
clang/lib/CodeGen/CGExpr.cpp | 3 +++
clang/test/CodeGen/glibc_ptr_align.c | 11 ++++++++---
2 files changed, 11 insertions(+), 3 deletions(-)
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index bba7d1e805f3f..e9e22321e2634 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4820,6 +4820,9 @@ bool
CodeGenFunction::isUnderlyingBasePointerConstantNull(const Expr *E) {
const Expr *UnderlyingBaseExpr = E->IgnoreParens();
while (auto *BaseMemberExpr = dyn_cast<MemberExpr>(UnderlyingBaseExpr))
UnderlyingBaseExpr = BaseMemberExpr->getBase()->IgnoreParens();
+ if (auto *Select = dyn_cast<ConditionalOperator>(UnderlyingBaseExpr))
+ return isUnderlyingBasePointerConstantNull(Select->getTrueExpr()) ||
+ isUnderlyingBasePointerConstantNull(Select->getFalseExpr());
return getContext().isSentinelNullExpr(UnderlyingBaseExpr);
}
diff --git a/clang/test/CodeGen/glibc_ptr_align.c
b/clang/test/CodeGen/glibc_ptr_align.c
index ebdb53cf7b53d..14968a8326509 100644
--- a/clang/test/CodeGen/glibc_ptr_align.c
+++ b/clang/test/CodeGen/glibc_ptr_align.c
@@ -3,10 +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 noundef ptr @glibc_ptr_align(
-// CHECK-SAME: ptr noundef readnone captures(none) [[BASE:%.*]], ptr noundef
readnone captures(none) [[POINTER:%.*]], i64 noundef [[ALIGN_MASK:%.*]])
local_unnamed_addr #[[ATTR0:[0-9]+]] {
+// CHECK-LABEL: define dso_local noalias 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: ret ptr null
+// 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 i8, ptr null, i64 [[AND]]
+// CHECK-NEXT: ret ptr [[ADD_PTR]]
//
char *glibc_ptr_align(char *base, char *pointer, long align_mask) {
return (sizeof(long int) < sizeof(void *) ? (base) : (char *)0) +
>From e9954e1afd3dca5ab9be60e0a3d69573f2db316a Mon Sep 17 00:00:00 2001
From: Yingwei Zheng <dtcxzyw2...@gmail.com>
Date: Wed, 30 Apr 2025 15:25:21 +0800
Subject: [PATCH 4/4] [Clang][CodeGen] Try to constant fold conditions
---
clang/lib/CodeGen/CGExpr.cpp | 12 ++++++---
clang/test/CodeGen/glibc_ptr_align.c | 40 ++++++++++++++++++++++++++++
2 files changed, 49 insertions(+), 3 deletions(-)
diff --git a/clang/lib/CodeGen/CGExpr.cpp b/clang/lib/CodeGen/CGExpr.cpp
index e9e22321e2634..d504855c5e882 100644
--- a/clang/lib/CodeGen/CGExpr.cpp
+++ b/clang/lib/CodeGen/CGExpr.cpp
@@ -4820,9 +4820,15 @@ bool
CodeGenFunction::isUnderlyingBasePointerConstantNull(const Expr *E) {
const Expr *UnderlyingBaseExpr = E->IgnoreParens();
while (auto *BaseMemberExpr = dyn_cast<MemberExpr>(UnderlyingBaseExpr))
UnderlyingBaseExpr = BaseMemberExpr->getBase()->IgnoreParens();
- if (auto *Select = dyn_cast<ConditionalOperator>(UnderlyingBaseExpr))
- return isUnderlyingBasePointerConstantNull(Select->getTrueExpr()) ||
- isUnderlyingBasePointerConstantNull(Select->getFalseExpr());
+ // Workaround for old glibc's __PTR_ALIGN macro
+ // If the condition can be constant evaluated, we check the selected arm.
+ if (auto *Select = dyn_cast<ConditionalOperator>(UnderlyingBaseExpr)) {
+ if (auto *C = dyn_cast_if_present<llvm::Constant>(
+ ConstantEmitter(*this).tryEmitAbstract(
+ Select->getCond(), Select->getCond()->getType())))
+ return isUnderlyingBasePointerConstantNull(
+ C->isNullValue() ? Select->getFalseExpr() : Select->getTrueExpr());
+ }
return getContext().isSentinelNullExpr(UnderlyingBaseExpr);
}
diff --git a/clang/test/CodeGen/glibc_ptr_align.c
b/clang/test/CodeGen/glibc_ptr_align.c
index 14968a8326509..2c628273e13ed 100644
--- a/clang/test/CodeGen/glibc_ptr_align.c
+++ b/clang/test/CodeGen/glibc_ptr_align.c
@@ -20,3 +20,43 @@ char *glibc_ptr_align(char *base, char *pointer, long
align_mask) {
(align_mask)) &
~(align_mask));
}
+
+// CHECK-LABEL: define dso_local noalias 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 i8, ptr null, i64 [[AND]]
+// CHECK-NEXT: ret ptr [[ADD_PTR]]
+//
+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));
+}
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