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Previously we checked isCLZForZeroUndef and only added UBSan checks
if it returned true.
The builtin should be considered undefined for 0 regardless of
the target so that code using it is portable. The isCLZForZeroUndef
was only intended to disable optimizations in the middle end and
backend.
See
https://discourse.llvm.org/t/should-ubsan-detect-0-input-to-builtin-clz-ctz-regardless-of-target/71060
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D152023
Files:
clang/lib/CodeGen/CGBuiltin.cpp
clang/test/CodeGen/ubsan-builtin-checks.c
Index: clang/test/CodeGen/ubsan-builtin-checks.c
===================================================================
--- clang/test/CodeGen/ubsan-builtin-checks.c
+++ clang/test/CodeGen/ubsan-builtin-checks.c
@@ -1,7 +1,8 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -w -emit-llvm -o - %s
-fsanitize=builtin | FileCheck %s
-// RUN: %clang_cc1 -triple arm64-none-linux-gnu -w -emit-llvm -o - %s
-fsanitize=builtin | FileCheck %s --check-prefix=NOT-UB
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -w -emit-llvm -o - %s
-fsanitize=builtin | FileCheck %s --check-prefixes=CHECK,POISON
+// RUN: %clang_cc1 -triple arm64-none-linux-gnu -w -emit-llvm -o - %s
-fsanitize=builtin | FileCheck %s --check-prefixes=CHECK,NOPOISON
-// NOT-UB-NOT: __ubsan_handle_invalid_builtin
+// A zero input to __bultin_ctz/clz is considered UB even if the target does
not
+// want to optimize based on zero input being undefined.
// CHECK: define{{.*}} void @check_ctz
void check_ctz(int n) {
@@ -13,7 +14,8 @@
// CHECK-NEXT: unreachable
//
// Continuation block:
- // CHECK: call i32 @llvm.cttz.i32(i32 [[N]], i1 true)
+ // POISON: call i32 @llvm.cttz.i32(i32 [[N]], i1 true)
+ // NOPOISON: call i32 @llvm.cttz.i32(i32 [[N]], i1 false)
__builtin_ctz(n);
// CHECK: call void @__ubsan_handle_invalid_builtin
@@ -33,7 +35,8 @@
// CHECK-NEXT: unreachable
//
// Continuation block:
- // CHECK: call i32 @llvm.ctlz.i32(i32 [[N]], i1 true)
+ // POISON: call i32 @llvm.ctlz.i32(i32 [[N]], i1 true)
+ // NOPOISON: call i32 @llvm.ctlz.i32(i32 [[N]], i1 false)
__builtin_clz(n);
// CHECK: call void @__ubsan_handle_invalid_builtin
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -1741,7 +1741,7 @@
&& "Unsupported builtin check kind");
Value *ArgValue = EmitScalarExpr(E);
- if (!SanOpts.has(SanitizerKind::Builtin) || !getTarget().isCLZForZeroUndef())
+ if (!SanOpts.has(SanitizerKind::Builtin))
return ArgValue;
SanitizerScope SanScope(this);
Index: clang/test/CodeGen/ubsan-builtin-checks.c
===================================================================
--- clang/test/CodeGen/ubsan-builtin-checks.c
+++ clang/test/CodeGen/ubsan-builtin-checks.c
@@ -1,7 +1,8 @@
-// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -w -emit-llvm -o - %s -fsanitize=builtin | FileCheck %s
-// RUN: %clang_cc1 -triple arm64-none-linux-gnu -w -emit-llvm -o - %s -fsanitize=builtin | FileCheck %s --check-prefix=NOT-UB
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -w -emit-llvm -o - %s -fsanitize=builtin | FileCheck %s --check-prefixes=CHECK,POISON
+// RUN: %clang_cc1 -triple arm64-none-linux-gnu -w -emit-llvm -o - %s -fsanitize=builtin | FileCheck %s --check-prefixes=CHECK,NOPOISON
-// NOT-UB-NOT: __ubsan_handle_invalid_builtin
+// A zero input to __bultin_ctz/clz is considered UB even if the target does not
+// want to optimize based on zero input being undefined.
// CHECK: define{{.*}} void @check_ctz
void check_ctz(int n) {
@@ -13,7 +14,8 @@
// CHECK-NEXT: unreachable
//
// Continuation block:
- // CHECK: call i32 @llvm.cttz.i32(i32 [[N]], i1 true)
+ // POISON: call i32 @llvm.cttz.i32(i32 [[N]], i1 true)
+ // NOPOISON: call i32 @llvm.cttz.i32(i32 [[N]], i1 false)
__builtin_ctz(n);
// CHECK: call void @__ubsan_handle_invalid_builtin
@@ -33,7 +35,8 @@
// CHECK-NEXT: unreachable
//
// Continuation block:
- // CHECK: call i32 @llvm.ctlz.i32(i32 [[N]], i1 true)
+ // POISON: call i32 @llvm.ctlz.i32(i32 [[N]], i1 true)
+ // NOPOISON: call i32 @llvm.ctlz.i32(i32 [[N]], i1 false)
__builtin_clz(n);
// CHECK: call void @__ubsan_handle_invalid_builtin
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -1741,7 +1741,7 @@
&& "Unsupported builtin check kind");
Value *ArgValue = EmitScalarExpr(E);
- if (!SanOpts.has(SanitizerKind::Builtin) || !getTarget().isCLZForZeroUndef())
+ if (!SanOpts.has(SanitizerKind::Builtin))
return ArgValue;
SanitizerScope SanScope(this);
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