[stubs] Implement unsigned/signed div/mod ti3 for Win64 #13295
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and use unsigned int directly instead of Compiler-RT's equivalent su_int.
| #define SWIFT_MODE_TI __attribute__((__mode__(TI))) | ||
| #else | ||
| #define SWIFT_MODE_DI | ||
| #define SWIFT_MODE_TI |
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Please make this a hard error. Without this, the types are completely the wrong size and you do not get any type of warning/error that things went wrong.
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The problem with a hard error is that I moved this out of the #if blocks, since the definitions are used by multiple disjoint if blocks. If we hard error, then that applies to every platform, even ones that will never need to use the types.
The alternatives would be to either warn or to duplicate these definitions and move them back into each #if block. The problem that then arises is that the definitions become conditional on what #if blocks we'd already encountered, unless we #defined and #undefd the types within each block.
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I've addressed this by adding a 3-line check for __mode__ support within each #if block.
stdlib/public/stubs/Stubs.cpp
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| #if defined(_WIN64) | ||
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| #define CHAR_BIT 8 // number of bits in a char |
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Can we not use the standard headers for this?
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Yes, sorry. I was blindly following Compiler-RT here, but it's already defined from <limits.h>.
| du_int low; | ||
| du_int high; | ||
| }s; | ||
| } utwords; |
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This technically is a GNU extension (union fields may only be access through initialized fields) and breaks aliasing. At that point, you should assume that the __mode__ extension is available
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@gparker42 When you get a chance, could you take a look at this in comparison to #13234 and see which approach you prefer? |
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Currently, |
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Okay, great. I’ll close these two PRs. |
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On Windows 64-bit, the
dividingFullWidthmethod onUInt64andInt64causes LLVM to emit references toudivti3,umodti3,divti3, andmodti3, which are undefined on Windows. Provide an implementation here based on Compiler-RT.This is an alternative fix to #13234.
cc @gparker42