2b5f68a5f6
This implements the C++23 `[[assume]]` attribute. Assumption information is lowered to a call to `@llvm.assume`, unless the expression has side-effects, in which case it is discarded and a warning is issued to tell the user that the assumption doesn’t do anything. A failed assumption at compile time is an error (unless we are in `MSVCCompat` mode, in which case we don’t check assumptions at compile time). Due to performance regressions in LLVM, assumptions can be disabled with the `-fno-assumptions` flag. With it, assumptions will still be parsed and checked, but no calls to `@llvm.assume` will be emitted and assumptions will not be checked at compile time.
19 lines
660 B
C++
19 lines
660 B
C++
// RUN: %clang_cc1 -std=c++23 -x c++ %s -verify
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void f(int x, int y) {
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[[assume(true)]];
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[[assume(1)]];
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[[assume(1.0)]];
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[[assume(1 + 2 == 3)]];
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[[assume(x ? 1 : 2)]];
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[[assume(x && y)]];
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[[assume(true)]] [[assume(true)]];
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[[assume]]; // expected-error {{takes one argument}}
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[[assume(]]; // expected-error {{expected expression}}
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[[assume()]]; // expected-error {{expected expression}}
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[[assume(2]]; // expected-error {{expected ')'}} expected-note {{to match this '('}}
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[[assume(x = 2)]]; // expected-error {{requires parentheses}}
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[[assume(2, 3)]]; // expected-error {{requires parentheses}} expected-warning {{has no effect}}
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}
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