llvm dev - Jan 2010 - [LLVMdev] safe to speculatively execute load of malloc?

I've just noticed this, in Instruction::isSafeToSpeculativelyExecute():

http://llvm.org/doxygen/Instruction_8cpp-source.html#l00408

00430   case Load: {
00431     if (cast<LoadInst>(this)->isVolatile())
00432       return false;
00433     if (isa<AllocaInst>(getOperand(0)) || isMalloc(getOperand(0)))
00434       return true;

This says that it's safe to speculatively execute a load from the
pointer returned by malloc(). But surely that's not true if malloc()
returns NULL.

Thanks,
Jay.

You're right, fixed in r92452.

-Chris

On Jan 3, 2010, at 4:54 AM, Jay Foad wrote:
> I've just noticed this, in Instruction::isSafeToSpeculativelyExecute():
> 
> http://llvm.org/doxygen/Instruction_8cpp-source.html#l00408
> 
> 00430   case Load: {
> 00431     if (cast<LoadInst>(this)->isVolatile())
> 00432       return false;
> 00433     if (isa<AllocaInst>(getOperand(0)) ||
isMalloc(getOperand(0)))
> 00434       return true;
> 
> This says that it's safe to speculatively execute a load from the
> pointer returned by malloc(). But surely that's not true if malloc()
> returns NULL.
> 
> Thanks,
> Jay.
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