[llvm-commits] [llvm] r66976 - in /llvm/trunk: lib/CodeGen/PHIElimination.cpp lib/Transforms/Scalar/CodeGenPrepare.cpp test/CodeGen/X86/2009-03-13-PHIElimBug.ll test/CodeGen/X86/split-eh-lpad-edges.ll

[Evan Cheng]

The copies are inserted by sdisel for liveout invoke return values.  
Your fix is doing the right thing now. What are the other issues?

Evan

On Mar 17, 2009, at 10:12 AM, Evan Cheng wrote:

> I'll look at these today.
>
> Evan
>
> On Mar 16, 2009, at 12:39 AM, Duncan Sands wrote:
>
>> Hi Evan,
>>
>>>>      %reg1031<def> = MOV32rr %EAX
>>>>      EH_LABEL 2
>>>>      %reg1025<def> = MOV32rr %reg1031  <= Invoke result, not an
>>>> EH_LABEL
>>>>      JMP mbb<entry.cont_crit_edge,0xa11af90>
>>>>
>>>> So in this case the logic bails out, putting the copy at the end of
>>>> the BB,
>>>> even though it might still need to be before the invoke.
>>>
>>> Something seems wrong with this. Who inserted the copy? The copy  
>>> from
>>> EAX to reg1031 is the copy lowered by isel. Is PHI elimination
>>> inserting the copy from reg1031 to reg1025? Then it should have done
>>> the right thing.
>>
>> I'm not sure where it's coming from (see testcase below).  By the
>> way, what
>> do you think of the patch I sent?  It's more efficient in the common
>> case of
>> an invoke with one def/use of SrcReg in the basic block, but less
>> efficient
>> when there is more than one def/use because it has to walk more of
>> the basic
>> block.
>>
>> Ciao,
>>
>> Duncan.
>>
>> Run: llc -march=x86 -f phi.bc
>>
>> If I break on WalkPassEHTryRange, then the first time I hit the
>> breakpoint
>> I see such a register copy after the EH_LABEL.  This is the MBB for
>> "cont",
>> and it is trying to find a place to put the copy for the phi node in
>> the
>> landing pad.
>>
>> declare i32 @f()
>>
>> declare i32 @g()
>>
>> define i32 @phi() {
>> entry:
>> 	%a = call i32 @f()		; <i32> [#uses=1]
>> 	%b = invoke i32 @g()
>> 			to label %cont unwind label %lpad		; <i32> [#uses=1]
>>
>> cont:		; preds = %entry
>> 	%x = phi i32 [ %b, %entry ]		; <i32> [#uses=0]
>> 	%aa = call i32 @f()		; <i32> [#uses=1]
>> 	%bb = invoke i32 @g()
>> 			to label %cont2 unwind label %lpad		; <i32> [#uses=1]
>>
>> cont2:		; preds = %cont
>> 	%xx = phi i32 [ %bb, %cont ]		; <i32> [#uses=1]
>> 	ret i32 %xx
>>
>> lpad:		; preds = %cont, %entry
>> 	%y = phi i32 [ %a, %entry ], [ %aa, %cont ]		; <i32> [#uses=1]
>> 	ret i32 %y
>> }
>
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