eee944e7f9
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
20 lines
648 B
C++
20 lines
648 B
C++
// RUN: %clang_cc1 -O3 -std=c++2a -S -emit-llvm -o - -disable-llvm-passes -triple x86_64-apple-macos10.14 %s | FileCheck %s
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void test_scalar() {
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// CHECK-LABEL: define void @_Z11test_scalarv
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__builtin_bit_cast(float, 42);
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// CHECK: load float, float* {{.*}}, align 4, !tbaa ![[MAY_ALIAS_TBAA:.*]]
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}
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void test_scalar2() {
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// CHECK-LABEL: define void @_Z12test_scalar2v
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struct S {int m;};
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__builtin_bit_cast(int, S{42});
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// CHECK: load i32, i32* {{.*}}, align 4, !tbaa ![[MAY_ALIAS_TBAA]]
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}
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// CHECK: ![[CHAR_TBAA:.*]] = !{!"omnipotent char", {{.*}}, i64 0}
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// CHECK: ![[MAY_ALIAS_TBAA]] = !{![[CHAR_TBAA]], ![[CHAR_TBAA]], i64 0}
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