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X86 can generate movb al, eax ? #1443

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llvmbot opened this issue Jan 3, 2007 · 1 comment
Closed

X86 can generate movb al, eax ? #1443

llvmbot opened this issue Jan 3, 2007 · 1 comment
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backend:X86 bugzilla Issues migrated from bugzilla compile-fail Use [accepts-invalid] and [rejects-valid] instead invalid Resolved as invalid, i.e. not a bug

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@llvmbot
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llvmbot commented Jan 3, 2007

Bugzilla Link 1071
Resolution INVALID
Resolved on Feb 22, 2010 12:52
Version trunk
OS Linux
Reporter LLVM Bugzilla Contributor

Extended Description

While testing this function:

define bool i32() { ret bool true; }

I noticed that it is possible for the X86 backend to generate:

movb al, eax

which doesn't assemble.

To make this happen, go to CodeGen/SelectionISel.cpp in the visitRetInst
function and make it not do an extend (of any kind) for boolean. This will
cause the Legalizer to apply an ANY_EXTEND which, presumably, means that not
doing an extend is okay. While that change is not correct, the X86 backend
shouldn't generate incorrect instructions either.
@llvmbot
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llvmbot commented Jan 3, 2007

Looks like legalizer isn't inserting an anyext to i32 so we ended up with a movb
with a 32-bit register destination.

If you let visitRet insert the anyext node, then it will not generate this
illegal instruction.

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 3, 2021
This issue was closed.
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backend:X86 bugzilla Issues migrated from bugzilla compile-fail Use [accepts-invalid] and [rejects-valid] instead invalid Resolved as invalid, i.e. not a bug
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