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llvm-project/clang/test/CodeGenCXX/builtin-bit-cast-no-tbaa.cpp

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[C++2a] Add __builtin_bit_cast, used to implement std::bit_cast This commit adds a new builtin, __builtin_bit_cast(T, v), which performs a bit_cast from a value v to a type T. This expression can be evaluated at compile time under specific circumstances. The compile time evaluation currently doesn't support bit-fields, but I'm planning on fixing this in a follow up (some of the logic for figuring this out is in CodeGen). I'm also planning follow-ups for supporting some more esoteric types that the constexpr evaluator supports, as well as extending __builtin_memcpy constexpr evaluation to use the same infrastructure. rdar://44987528 Differential revision: https://reviews.llvm.org/D62825 llvm-svn: 364954
2019-07-03 02:28:13 +08:00
// RUN: %clang_cc1 -O3 -std=c++2a -S -emit-llvm -o - -disable-llvm-passes -triple x86_64-apple-macos10.14 %s | FileCheck %s
void test_scalar() {
// CHECK-LABEL: define void @_Z11test_scalarv
__builtin_bit_cast(float, 42);
// CHECK: load float, float* {{.*}}, align 4, !tbaa ![[MAY_ALIAS_TBAA:.*]]
}
void test_scalar2() {
// CHECK-LABEL: define void @_Z12test_scalar2v
struct S {int m;};
__builtin_bit_cast(int, S{42});
// CHECK: load i32, i32* {{.*}}, align 4, !tbaa ![[MAY_ALIAS_TBAA]]
}
// CHECK: ![[CHAR_TBAA:.*]] = !{!"omnipotent char", {{.*}}, i64 0}
// CHECK: ![[MAY_ALIAS_TBAA]] = !{![[CHAR_TBAA]], ![[CHAR_TBAA]], i64 0}