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llvm-project/clang/test/CodeGen/padding-init.c

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Variable auto-init: don't initialize aggregate padding of all aggregates Summary: C guarantees that brace-init with fewer initializers than members in the aggregate will initialize the rest of the aggregate as-if it were static initialization. In turn static initialization guarantees that padding is initialized to zero bits. Quoth the Standard: C17 6.7.9 Initialization ❡21 If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration. C17 6.7.9 Initialization ❡10 If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static or thread storage duration is not initialized explicitly, then: * if it has pointer type, it is initialized to a null pointer; * if it has arithmetic type, it is initialized to (positive or unsigned) zero; * if it is an aggregate, every member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; * if it is a union, the first named member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; <rdar://problem/50188861> Reviewers: glider, pcc, kcc, rjmccall, erik.pilkington Subscribers: jkorous, dexonsmith, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D61280 llvm-svn: 359628
2019-05-01 06:56:53 +08:00
// RUN: %clang_cc1 -triple x86_64-unknown-unknown -ftrivial-auto-var-init=pattern %s -emit-llvm -o - | FileCheck %s
// RUN: %clang_cc1 -triple x86_64-unknown-unknown -ftrivial-auto-var-init=zero %s -emit-llvm -o - | FileCheck %s
// C guarantees that brace-init with fewer initializers than members in the
// aggregate will initialize the rest of the aggregate as-if it were static
// initialization. In turn static initialization guarantees that padding is
// initialized to zero bits.
// CHECK: @__const.partial_init.s = private unnamed_addr constant { i8, [7 x i8], i64 } { i8 42, [7 x i8] zeroinitializer, i64 0 }, align 8
// Technically, we could initialize this padding to non-zero because all of the
// struct's members have initializers.
// CHECK: @__const.init_all.s = private unnamed_addr constant { i8, [7 x i8], i64 } { i8 42, [7 x i8] zeroinitializer, i64 -2401053089374216531 }, align 8
struct S {
char c;
long long l;
};
void use(struct S*);
// CHECK-LABEL: @empty_braces(
// CHECK: %s = alloca
// CHECK-NEXT: %[[B:[0-9+]]] = bitcast %struct.S* %s to i8*
// CHECK-NEXT: call void @llvm.memset{{.*}}(i8* align 8 %[[B]], i8 0,
[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions. I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default. Test updates are made as a separate patch: D108453 Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D105169
2022-01-16 17:53:11 +08:00
// CHECK-NEXT: call void @use(%struct.S* noundef %s)
Variable auto-init: don't initialize aggregate padding of all aggregates Summary: C guarantees that brace-init with fewer initializers than members in the aggregate will initialize the rest of the aggregate as-if it were static initialization. In turn static initialization guarantees that padding is initialized to zero bits. Quoth the Standard: C17 6.7.9 Initialization ❡21 If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration. C17 6.7.9 Initialization ❡10 If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static or thread storage duration is not initialized explicitly, then: * if it has pointer type, it is initialized to a null pointer; * if it has arithmetic type, it is initialized to (positive or unsigned) zero; * if it is an aggregate, every member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; * if it is a union, the first named member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; <rdar://problem/50188861> Reviewers: glider, pcc, kcc, rjmccall, erik.pilkington Subscribers: jkorous, dexonsmith, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D61280 llvm-svn: 359628
2019-05-01 06:56:53 +08:00
void empty_braces() {
struct S s = {};
return use(&s);
}
// CHECK-LABEL: @partial_init(
// CHECK: %s = alloca
// CHECK-NEXT: %[[B:[0-9+]]] = bitcast %struct.S* %s to i8*
// CHECK-NEXT: call void @llvm.memcpy{{.*}}(i8* align 8 %[[B]], {{.*}}@__const.partial_init.s
[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions. I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default. Test updates are made as a separate patch: D108453 Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D105169
2022-01-16 17:53:11 +08:00
// CHECK-NEXT: call void @use(%struct.S* noundef %s)
Variable auto-init: don't initialize aggregate padding of all aggregates Summary: C guarantees that brace-init with fewer initializers than members in the aggregate will initialize the rest of the aggregate as-if it were static initialization. In turn static initialization guarantees that padding is initialized to zero bits. Quoth the Standard: C17 6.7.9 Initialization ❡21 If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration. C17 6.7.9 Initialization ❡10 If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static or thread storage duration is not initialized explicitly, then: * if it has pointer type, it is initialized to a null pointer; * if it has arithmetic type, it is initialized to (positive or unsigned) zero; * if it is an aggregate, every member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; * if it is a union, the first named member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; <rdar://problem/50188861> Reviewers: glider, pcc, kcc, rjmccall, erik.pilkington Subscribers: jkorous, dexonsmith, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D61280 llvm-svn: 359628
2019-05-01 06:56:53 +08:00
void partial_init() {
struct S s = { .c = 42 };
return use(&s);
}
// CHECK-LABEL: @init_all(
// CHECK: %s = alloca
// CHECK-NEXT: %[[B:[0-9+]]] = bitcast %struct.S* %s to i8*
// CHECK-NEXT: call void @llvm.memcpy{{.*}}(i8* align 8 %[[B]], {{.*}}@__const.init_all.s
[Clang/Test]: Rename enable_noundef_analysis to disable-noundef-analysis and turn it off by default Turning on `enable_noundef_analysis` flag allows better codegen by removing freeze instructions. I modified clang by renaming `enable_noundef_analysis` flag to `disable-noundef-analysis` and turning it off by default. Test updates are made as a separate patch: D108453 Reviewed By: eugenis Differential Revision: https://reviews.llvm.org/D105169
2022-01-16 17:53:11 +08:00
// CHECK-NEXT: call void @use(%struct.S* noundef %s)
Variable auto-init: don't initialize aggregate padding of all aggregates Summary: C guarantees that brace-init with fewer initializers than members in the aggregate will initialize the rest of the aggregate as-if it were static initialization. In turn static initialization guarantees that padding is initialized to zero bits. Quoth the Standard: C17 6.7.9 Initialization ❡21 If there are fewer initializers in a brace-enclosed list than there are elements or members of an aggregate, or fewer characters in a string literal used to initialize an array of known size than there are elements in the array, the remainder of the aggregate shall be initialized implicitly the same as objects that have static storage duration. C17 6.7.9 Initialization ❡10 If an object that has automatic storage duration is not initialized explicitly, its value is indeterminate. If an object that has static or thread storage duration is not initialized explicitly, then: * if it has pointer type, it is initialized to a null pointer; * if it has arithmetic type, it is initialized to (positive or unsigned) zero; * if it is an aggregate, every member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; * if it is a union, the first named member is initialized (recursively) according to these rules, and any padding is initialized to zero bits; <rdar://problem/50188861> Reviewers: glider, pcc, kcc, rjmccall, erik.pilkington Subscribers: jkorous, dexonsmith, cfe-commits Tags: #clang Differential Revision: https://reviews.llvm.org/D61280 llvm-svn: 359628
2019-05-01 06:56:53 +08:00
void init_all() {
struct S s = { .c = 42, .l = 0xdeadbeefc0fedead };
return use(&s);
}