[Sema] Fixed faulty shift count warning #1
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Constant values of _BitInt have the bitwith to exactly fit the constant number. This patch fix a problem in Sema when building an APInt where the supplied bitwidth can become too small and simply truncate the value leading to a faulty warning.
karka228
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Jun 24, 2024
…on (llvm#94752) Fixes llvm#62925. The following code: ```cpp #include <map> int main() { std::map m1 = {std::pair{"foo", 2}, {"bar", 3}}; // guide llvm#2 std::map m2(m1.begin(), m1.end()); // guide #1 } ``` Is rejected by clang, but accepted by both gcc and msvc: https://godbolt.org/z/6v4fvabb5 . So basically CTAD with copy-list-initialization is rejected. Note that this exact code is also used in a cppreference article: https://en.cppreference.com/w/cpp/container/map/deduction_guides I checked the C++11 and C++20 standard drafts to see whether suppressing user conversion is the correct thing to do for user conversions. Based on the standard I don't think that it is correct. ``` 13.3.1.4 Copy-initialization of class by user-defined conversion [over.match.copy] Under the conditions specified in 8.5, as part of a copy-initialization of an object of class type, a user-defined conversion can be invoked to convert an initializer expression to the type of the object being initialized. Overload resolution is used to select the user-defined conversion to be invoked ``` So we could use user defined conversions according to the standard. ``` If a narrowing conversion is required to initialize any of the elements, the program is ill-formed. ``` We should not do narrowing. ``` In copy-list-initialization, if an explicit constructor is chosen, the initialization is ill-formed. ``` We should not use explicit constructors.
karka228
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Jun 24, 2024
`rethrow` instruction is a terminator, but when when its DAG is built in `SelectionDAGBuilder` in a custom routine, it was NOT treated as such. ```ll rethrow: ; preds = %catch.start invoke void @llvm.wasm.rethrow() #1 [ "funclet"(token %1) ] to label %unreachable unwind label %ehcleanup ehcleanup: ; preds = %rethrow, %catch.dispatch %tmp = phi i32 [ 10, %catch.dispatch ], [ 20, %rethrow ] ... ``` In this bitcode, because of the `phi`, a `CONST_I32` will be created in the `rethrow` BB. Without this patch, the DAG for the `rethrow` BB looks like this: ``` t0: ch,glue = EntryToken t3: ch = CopyToReg t0, Register:i32 %9, Constant:i32<20> t5: ch = llvm.wasm.rethrow t0, TargetConstant:i32<12161> t6: ch = TokenFactor t3, t5 t8: ch = br t6, BasicBlock:ch<unreachable 0x562532e43c50> ``` Note that `CopyToReg` and `llvm.wasm.rethrow` don't have dependence so either can come first in the selected code, which can result in the code like ```mir bb.3.rethrow: RETHROW 0, implicit-def dead $arguments %9:i32 = CONST_I32 20, implicit-def dead $arguments BR %bb.6, implicit-def dead $arguments ``` After this patch, `llvm.wasm.rethrow` is treated as a terminator, and the DAG will look like ``` t0: ch,glue = EntryToken t3: ch = CopyToReg t0, Register:i32 %9, Constant:i32<20> t5: ch = llvm.wasm.rethrow t3, TargetConstant:i32<12161> t7: ch = br t5, BasicBlock:ch<unreachable 0x5555e3d32c70> ``` Note that now `rethrow` takes a token from `CopyToReg`, so `rethrow` has to come after `CopyToReg`. And the resulting code will be ```mir bb.3.rethrow: %9:i32 = CONST_I32 20, implicit-def dead $arguments RETHROW 0, implicit-def dead $arguments BR %bb.6, implicit-def dead $arguments ``` I'm not very familiar with the internals of `getRoot` vs. `getControlRoot`, but other terminator instructions seem to use the latter, and using it for `rethrow` too worked.
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Constant values of _BitInt have the bitwith to exactly fit the constant
number. This patch fix a problem in Sema when building an APInt where the
supplied bitwidth can become too small and simply truncate the value leading to
a faulty warning.