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[llvm-gcc] llvm-gcc lays out bitfields backwards on big endian systems #966

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lattner opened this issue Jul 14, 2005 · 2 comments
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[llvm-gcc] llvm-gcc lays out bitfields backwards on big endian systems #966

lattner opened this issue Jul 14, 2005 · 2 comments
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bugzilla Issues migrated from bugzilla llvm-tools All llvm tools that do not have corresponding tag miscompilation

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lattner commented Jul 14, 2005

Bugzilla Link 594
Resolution FIXED
Resolved on Feb 22, 2010 12:51
Version 1.0
OS MacOS X

Extended Description

This program is miscompiled by LLVM on powerpc. It appears that bitfields are
being layed out backwards by the CFE. This may be related to Bug 449. It
probably also affects Sparc. This testcase should be compiled with
-fno-strict-aliasing.

-Chris

struct X {
int A : 4;
int Z : 28;
};

void test(struct X *P, int A) {
P->A = A;
}

int main() {
int Y = ~0;
test((struct X*)&Y, 0);
printf("%x\n", Y);
}
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lattner commented Jul 14, 2005

assigned to @lattner

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lattner commented Jul 21, 2005

Fixed. Patches here and here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050711/027100.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20050718/027152.html

Fixing this fixes NAMD, 176.gcc and others.

-Chris

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 3, 2021
keryell pushed a commit to keryell/llvm-project that referenced this issue Oct 19, 2024
@mvvsmk @lanza
[CIR][CIRGen][Builtin][Type] Support for IEEE Quad (long double) adde…
0d894e1 
…d (in CIR + Direct to LLVM) (llvm#966)

Fixes llvm/clangir#931
Added type definition in CIRTypes.td, created appropriate functions for
the same in CIRTypes.cpp like getPreferredAlignment,
getPreferredAlignment, etc. Optionally added lowering in LowerToLLVM.cpp
xlauko pushed a commit to trailofbits/instafix-llvm that referenced this issue Mar 28, 2025
@mvvsmk @xlauko
[CIR][CIRGen][Builtin][Type] Support for IEEE Quad (long double) adde…
5a767e7 
…d (in CIR + Direct to LLVM) (llvm#966)

Fixes llvm/clangir#931
Added type definition in CIRTypes.td, created appropriate functions for
the same in CIRTypes.cpp like getPreferredAlignment,
getPreferredAlignment, etc. Optionally added lowering in LowerToLLVM.cpp
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