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This commit is debatable. There are two possible approaches, neither of which is really satisfactory: 1. Use "@foo(i1 zeroext)" to mean an extension to 32-bits on Darwin, and 8 bits otherwise. 2. Redefine "@foo(i1)" to mean that the i1 is extended by the caller to 8 bits. This goes against the spirit of "zeroext" I think, but it's a bit of a vague construct anyway (by definition you're going to extend to the amount required by the ABI, that's why it's the ABI!). This implements option 2. The DAG machinery really isn't setup for the first (there's a fairly strong assumption that "zeroext" goes to at least the smallest register size), and even if it was the resulting DAG looks like it would be inferior in many cases. Theoretically we could add AssertZext nodes in the consumers of ABI-passed values too now, but this actually seems to make the code worse in practice by making truncation proceed in two steps. The code produced is equally valid if we continue to assume only the low bit is defined. Should fix PR19850 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@209637 91177308-0d34-0410-b5e6-96231b3b80d8
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