C++: Support IRGuards with no implicit boolean conversion
#16364
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Co-authored-by: Jeroen Ketema <[email protected]>
geoffw0
approved these changes
Apr 30, 2024
| // value.(BooleanValue).getValue() = true | ||
| // ``` | ||
| // but all we know is that the value is non-zero in the true branch. | ||
| // So we can only conclude something in the false branch. |
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What would be the consequences if we included common values for true (namely 1 and -1)? Would any results be wrong, or just incomplete?
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Results would be wrong. For example, consider this example:
void foo(char* p) {
if(p) { // assume we uncommented the above so that we inferred that `p == 1` is implied by this
if(p == 1) { // I know this is a weird comparison to do on a pointer, but oh well.
// We would conclude that this branch was always taken
}
}
}
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When this is compiled as C code:
there's no implicit conversion to boolean, and thus we don't generate a
CompareInstructionthat theIRGuardslibrary rely on.This PR adds a case to
IRGuardsso that we can also infer guards when noCompareInstructions are present in the condition