dd2362a8ba
A variable with `weak` attribute signifies that it can be replaced with a "strong" symbol link time. Therefore it must not emitted with "weak_odr" linkage, as that allows the backend to use its value in optimizations. The frontend already considers weak const variables as non-constant (note_constexpr_var_init_weak diagnostic) so this change makes frontend and backend consistent. This commit reverses the f49573d1 weak globals that are const should get weak_odr linkage. commit from 2009-08-05 which introduced this behavior. Unfortunately that commit doesn't provide any details on why the change was made. This was discussed in https://discourse.llvm.org/t/weak-attribute-semantics-on-const-variables/62311 Differential Revision: https://reviews.llvm.org/D126324
59 lines
1.8 KiB
C
59 lines
1.8 KiB
C
// RUN: %clang_cc1 -emit-llvm -o - -triple i386-linux-gnu %s | FileCheck %s
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// This checks that the global won't be marked as common.
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// (It shouldn't because it's being initialized).
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int a;
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int a = 242;
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// CHECK: @a ={{.*}} global i32 242
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// This should get normal weak linkage.
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int c __attribute__((weak))= 0;
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// CHECK: @c = weak global i32 0
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// Even though is marked const, it should get still get "weak"
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// linkage, not "weak_odr" as the weak attribute makes it possible
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// that there is a strong definition that changes the value linktime,
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// so the value must not be considered constant.
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// CHECK: @d = weak constant i32 0
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const int d __attribute__((weak))= 0;
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// However, "selectany" is similar to "weak", but isn't interposable
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// by a strong definition, and should appear as weak_odr.
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// CHECK: @e = weak_odr constant i32 17
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const int e __attribute__((selectany)) = 17;
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// PR6168 "too many undefs"
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struct ManyFields {
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int a;
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int b;
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int c;
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char d;
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int e;
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int f;
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};
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// CHECK: global %struct.ManyFields { i32 1, i32 2, i32 0, i8 0, i32 0, i32 0 }
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struct ManyFields FewInits = {1, 2};
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// PR6766
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// CHECK: @l ={{.*}} global %struct.K { [6 x i32] [i32 102, i32 111, i32 111, i32 0, i32 0, i32 0], i32 1 }
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typedef __WCHAR_TYPE__ wchar_t;
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struct K {
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wchar_t L[6];
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int M;
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} l = { { L"foo" }, 1 };
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// CHECK: @yuv_types ={{.*}} global [4 x [6 x i8]] {{\[}}[6 x i8] c"4:0:0\00", [6 x i8] c"4:2:0\00", [6 x i8] c"4:2:2\00", [6 x i8] c"4:4:4\00"]
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char yuv_types[4][6]= {"4:0:0","4:2:0","4:2:2","4:4:4"};
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// NOTE: tentative definitions are processed at the end of the translation unit.
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// This shouldn't be emitted as common because it has an explicit section.
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// rdar://7119244
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// CHECK: @b ={{.*}} global i32 0, section "foo"
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int b __attribute__((section("foo")));
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