[llvm-commits] [llvm] r57465 - in /llvm/trunk: lib/Target/X86/X86ISelDAGToDAG.cpp test/CodeGen/X86/pr2849.ll

[Evan Cheng]

Thanks. I am kinda confused by the fix though. I thought the problem  
was the AND node (i.e. N) has already been added to the isel queue so  
NewAND node will not be selected? The newly created shift node doesn't  
have a node id. Is that ok? Is it guaranteed that its lone use has  
already been processed?

Please add some comments because this is tricky stuff.

Thanks,

Evan

On Oct 13, 2008, at 1:52 PM, Dan Gohman wrote:

> Author: djg
> Date: Mon Oct 13 15:52:04 2008
> New Revision: 57465
>
> URL: http://llvm.org/viewvc/llvm-project?rev=57465&view=rev
> Log:
> When doing the very-late shift-and address-mode optimization,
> create a new DAG node to represent the new shift to keep the
> DAG consistent, even though it'll almost always be folded into
> the address.
>
> If a user of the resulting address has multiple uses, the
> nodes may get revisited by a later MatchAddress call, in which
> case DAG inconsistencies do matter.
>
> This fixes PR2849.
>
> Added:
>    llvm/trunk/test/CodeGen/X86/pr2849.ll
> Modified:
>    llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp
>
> Modified: llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp?rev=57465&r1=57464&r2=57465&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp (original)
> +++ llvm/trunk/lib/Target/X86/X86ISelDAGToDAG.cpp Mon Oct 13  
> 15:52:04 2008
> @@ -989,8 +989,11 @@
>                                            SDValue(C2, 0),  
> SDValue(C1, 0));
>     SDValue NewAND = CurDAG->getNode(ISD::AND, N.getValueType(),
>                                        Shift.getOperand(0),  
> NewANDMask);
> +    SDValue NewSHIFT = CurDAG->getNode(ISD::SHL, N.getValueType(),
> +                                       NewAND, SDValue(C1, 0));
>     NewANDMask.getNode()->setNodeId(Shift.getNode()->getNodeId());
>     NewAND.getNode()->setNodeId(N.getNode()->getNodeId());
> +    CurDAG->ReplaceAllUsesWith(N, NewSHIFT);
>
>     AM.Scale = 1 << ShiftCst;
>     AM.IndexReg = NewAND;
>
> Added: llvm/trunk/test/CodeGen/X86/pr2849.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/pr2849.ll?rev=57465&view=auto
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- llvm/trunk/test/CodeGen/X86/pr2849.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/pr2849.ll Mon Oct 13 15:52:04 2008
> @@ -0,0 +1,38 @@
> +; RUN: llvm-as < %s | llc
> +; PR2849
> +
> +target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32- 
> i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64- 
> s0:64:64-f80:128:128"
> +target triple = "x86_64-unknown-linux-gnu"
> +	%struct.BaseBoundPtrs = type { i8*, i8* }
> +	%struct.HashEntry = type { %struct.BaseBoundPtrs }
> +	%struct.NODE = type { i8, i8, %struct.anon }
> +	%struct.anon = type { %struct.xlist }
> +	%struct.xlist = type { %struct.NODE*, %struct.NODE* }
> +	%struct.xvect = type { %struct.NODE** }
> + at hash_table_begin = external global %struct.HashEntry*
> +
> +define void @obshow() {
> +entry:
> +	%tmp = load %struct.HashEntry** @hash_table_begin, align 8
> +	br i1 false, label %xlygetvalue.exit, label %xlygetvalue.exit
> +
> +xlygetvalue.exit:
> +	%storemerge.in.i = phi %struct.NODE** [ null, %entry ], [ null,  
> %entry ]
> +	%storemerge.i = load %struct.NODE** %storemerge.in.i
> +	%tmp1 = ptrtoint %struct.NODE** %storemerge.in.i to i64
> +	%tmp2 = lshr i64 %tmp1, 3
> +	%tmp3 = and i64 %tmp2, 2147483647
> +	%tmp4 = getelementptr %struct.HashEntry* %tmp, i64 %tmp3, i32 0,  
> i32 1
> +	%tmp7 = load i8** %tmp4, align 8
> +	%tmp8 = getelementptr %struct.NODE* %storemerge.i, i64 0, i32 2
> +	%tmp9 = bitcast %struct.anon* %tmp8 to %struct.NODE***
> +	%tmp11 = load %struct.NODE*** %tmp9, align 8
> +	%tmp12 = ptrtoint %struct.NODE** %tmp11 to i64
> +	%tmp13 = lshr i64 %tmp12, 3
> +	%tmp14 = and i64 %tmp13, 2147483647
> +	%tmp15 = getelementptr %struct.HashEntry* %tmp, i64 %tmp14, i32 0,  
> i32 1
> +	call fastcc void @xlprint(i8** %tmp4, i8* %tmp7, i8** %tmp15)
> +	ret void
> +}
> +
> +declare fastcc void @xlprint(i8**, i8*, i8**)
>
>
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