| Issue |
132628
|
| Summary |
Missed Optimization: comparing the result of a disjoint or with a constant can be simplified
|
| Labels |
new issue
|
| Assignees |
|
| Reporter |
Cancelll
|
godbolt: https://godbolt.org/z/KhbTx6jM5
Alive2: https://alive2.llvm.org/ce/z/dYuU3i
```llvm
define i1 @src1(ptr readonly captures(none) %0) local_unnamed_addr #0 {
%2 = getelementptr inbounds nuw i8, ptr %0, i64 1
%3 = load i8, ptr %2, align 1
%4 = zext i8 %3 to i32
%5 = shl nuw nsw i32 %4, 8
%6 = getelementptr inbounds nuw i8, ptr %0, i64 2
%7 = load i8, ptr %6, align 1
%8 = zext i8 %7 to i32
%9 = or disjoint i32 %5, %8
%10 = icmp ne i32 %9, 256
ret i1 %10
}
define i1 @tgt1(ptr readonly captures(none) %0) local_unnamed_addr #0 {
%2 = getelementptr inbounds nuw i8, ptr %0, i64 1
%3 = load i8, ptr %2, align 1
%4 = getelementptr inbounds nuw i8, ptr %0, i64 2
%5 = load i8, ptr %4, align 1
%6 = icmp ne i8 %3, 1
%7 = icmp ne i8 %5, 0
%8 = or i1 %6, %7
ret i1 %8
}
define i1 @src2(ptr readonly captures(none) %0) local_unnamed_addr #0 {
%2 = getelementptr inbounds nuw i8, ptr %0, i64 8
%3 = load i8, ptr %2, align 1
%4 = zext i8 %3 to i16
%5 = shl nuw i16 %4, 8
%6 = getelementptr inbounds nuw i8, ptr %0, i64 9
%7 = load i8, ptr %6, align 1
%8 = zext i8 %7 to i16
%9 = or disjoint i16 %5, %8
%.not103170.i = icmp eq i16 %9, 0
ret i1 %.not103170.i
}
define i1 @tgt2(ptr readonly captures(none) %0) local_unnamed_addr #0 {
%2 = getelementptr inbounds nuw i8, ptr %0, i64 8
%3 = load i8, ptr %2, align 1
%4 = getelementptr inbounds nuw i8, ptr %0, i64 9
%5 = load i8, ptr %4, align 1
%6 = or i8 %5, %3
%.not103170.i = icmp eq i8 %6, 0
ret i1 %.not103170.i
}
```
The first pattern is found here: https://github.com/dtcxzyw/llvm-opt-benchmark/blob/4eda6e7d8f48cfd3eadcc8778a1a557e670e2f08/bench/openssl/optimized/bad_dtls_test.ll#L685-L693
The second pattern is found here: https://github.com/dtcxzyw/llvm-opt-benchmark/blob/4eda6e7d8f48cfd3eadcc8778a1a557e670e2f08/bench/curl/optimized/doh.ll#L1139-L1147
Although in this case, the result of ```or disjoint``` is used else where, and thus probably cannot be optimized.
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