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[llvm-gcc] volatile lost in struct copy #1724

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sunfishcode opened this issue Apr 24, 2007 · 4 comments
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[llvm-gcc] volatile lost in struct copy #1724

sunfishcode opened this issue Apr 24, 2007 · 4 comments
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@lattner
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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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@sunfishcode
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Bugzilla Link 1352
Resolution FIXED
Resolved on Mar 06, 2010 14:00
Version 1.9
OS All

Extended Description

I typed this into the online demo:

struct foo {
int x;
};

void copy(volatile struct foo *p, struct foo *q)
{
*p = *q;
}

It produced this:

void %copy(%struct.foo* %p, %struct.foo* %q) {
entry:
%tmp2 = getelementptr %struct.foo* %q, int 0, uint 0 ; <int*> [#uses=1]
%tmp = load int* %tmp2 ; [#uses=1]
%tmp4 = getelementptr %struct.foo* %p, int 0, uint 0 ; <int*> [#uses=1]
store int %tmp, int* %tmp4
ret void
}

The store should be volatile.
@sunfishcode
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assigned to @lattner

@llvmbot
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llvmbot commented Apr 24, 2007

The assignment happens in this bit of TreeToLLVM::EmitMODIFY_EXPR,
with isVolatile=true and DestLoc=0:

// Non-bitfield aggregate value.
Emit(TREE_OPERAND(exp, 1), LV.Ptr); <== the assignment
if (DestLoc)
  EmitAggregateCopy(DestLoc, LV.Ptr, TREE_TYPE(exp), isVolatile, false);
return 0;

And indeed nothing marks the store as volatile.

@lattner
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lattner commented Apr 25, 2007

Verified that this is broken on mainline, investigating.

@lattner
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lattner commented Apr 25, 2007

Fixed. Patch here:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070423/048374.html

Testcase here: test/CFrontend/2007-04-24-VolatileStructCopy.c

Thanks!

-Chris

@llvmbot llvmbot transferred this issue from llvm/llvm-bugzilla-archive Dec 3, 2021
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