jayfoad wrote: This diff looks suspicious to me in function `_ZN22__llvm_libc_22_0_0_git8internal18CharacterConverter8pop_utf8Ev`: ```diff --- 01-preopt-good.txt 2025-09-05 10:39:57.226224451 +0100 +++ 01-preopt-bad.txt 2025-09-05 10:39:56.149207707 +0100 @@ -11112,10 +11113,10 @@ if.then4: ; preds = %if.end - %sub7 = add nsw i64 %conv, -1 - %4 = extractelement <4 x i8> <i8 0, i8 -64, i8 -32, i8 -16>, i64 %sub7 - %5 = load i32, ptr %0, align 4, !tbaa !58 + %4 = add nuw nsw i64 %conv, 4294967295 + %5 = extractelement <4 x i8> <i8 0, i8 -64, i8 -32, i8 -16>, i64 %4 + %6 = load i32, ptr %0, align 4, !tbaa !58 %sh_prom = trunc nuw nsw i64 %mul to i32 - %shr = lshr i32 %5, %sh_prom + %shr = lshr i32 %6, %sh_prom %shr.tr = trunc i32 %shr to i8 - %or.narrow = or i8 %4, %shr.tr - %6 = zext i8 %or.narrow to i32 + %or.narrow = or i8 %5, %shr.tr + %7 = zext i8 %or.narrow to i32 br label %if.end15 ``` I am guessing that the `add nsw i64 %conv, -1` vs `add nuw nsw i64 %conv, 4294967295` are the result of transforming some `getelementptr` instructions, and it seems suspicious that the 64-bit offset is small and negative in the good case but large and positive in the bad case.
https://github.com/llvm/llvm-project/pull/155415 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
