[llvm-commits] [llvm] r169951 - in /llvm/trunk: lib/CodeGen/SelectionDAG/DAGCombiner.cpp test/CodeGen/X86/store_op_load_fold.ll

[Eli Friedman]

On Tue, Dec 11, 2012 at 5:13 PM, Manman Ren <mren at apple.com> wrote:
> Author: mren
> Date: Tue Dec 11 19:13:50 2012
> New Revision: 169951
>
> URL: http://llvm.org/viewvc/llvm-project?rev=169951&view=rev
> Log:
> DAGCombine: clamp hi bit in APInt::getBitsSet to avoid assertion
>
> rdar://12838504
>
> Modified:
>     llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
>     llvm/trunk/test/CodeGen/X86/store_op_load_fold.ll
>
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=169951&r1=169950&r2=169951&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Tue Dec 11 19:13:50 2012
> @@ -7433,7 +7433,8 @@
>      // start at the previous one.
>      if (ShAmt % NewBW)
>        ShAmt = (((ShAmt + NewBW - 1) / NewBW) * NewBW) - NewBW;
> -    APInt Mask = APInt::getBitsSet(BitWidth, ShAmt, ShAmt + NewBW);
> +    APInt Mask = APInt::getBitsSet(BitWidth, ShAmt,
> +                                   std::min(BitWidth, ShAmt + NewBW));
>      if ((Imm & Mask) == Imm) {
>        APInt NewImm = (Imm & Mask).lshr(ShAmt).trunc(NewBW);
>        if (Opc == ISD::AND)

Are you sure the math here is actually correct?  This looks really
suspicious, especially without a comment explaining how the math is
supposed to work.

-Eli

> Modified: llvm/trunk/test/CodeGen/X86/store_op_load_fold.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/store_op_load_fold.ll?rev=169951&r1=169950&r2=169951&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/store_op_load_fold.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/store_op_load_fold.ll Tue Dec 11 19:13:50 2012
> @@ -1,13 +1,30 @@
> -; RUN: llc < %s -march=x86 | not grep mov
> +; RUN: llc < %s -march=x86 | FileCheck %s
>  ;
>  ; Test the add and load are folded into the store instruction.
>
>  @X = internal global i16 0              ; <i16*> [#uses=2]
>
>  define void @foo() nounwind {
> +; CHECK: foo:
> +; CHECK-NOT: mov
> +; CHECK: add
> +; CHECK_NEXT: ret
>          %tmp.0 = load i16* @X           ; <i16> [#uses=1]
>          %tmp.3 = add i16 %tmp.0, 329            ; <i16> [#uses=1]
>          store i16 %tmp.3, i16* @X
>          ret void
>  }
>
> +; rdar://12838504
> +%struct.S2 = type { i64, i16, [2 x i8], i8, [3 x i8], [7 x i8], i8, [8 x i8] }
> + at s2 = external global %struct.S2, align 16
> +define void @test2() nounwind uwtable ssp {
> +; CHECK: test2:
> +; CHECK: mov
> +; CHECK-NEXT: and
> +; CHECK-NEXT: ret
> +  %bf.load35 = load i56* bitcast ([7 x i8]* getelementptr inbounds (%struct.S2* @s2, i32 0, i32 5) to i56*), align 16
> +  %bf.clear36 = and i56 %bf.load35, -1125895611875329
> +  store i56 %bf.clear36, i56* bitcast ([7 x i8]* getelementptr inbounds (%struct.S2* @s2, i32 0, i32 5) to i56*), align 16
> +  ret void
> +}
>
>
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