[llvm] r284580 - [Thumb-1] Synthesize TBB/TBH instructions to make use of compressed jump tables

[Friedman, Eli via llvm-commits]

On 10/19/2016 5:06 AM, James Molloy via llvm-commits wrote:
> Author: jamesm
> Date: Wed Oct 19 07:06:49 2016
> New Revision: 284580
>
> URL: http://llvm.org/viewvc/llvm-project?rev=284580&view=rev
> Log:
> [Thumb-1] Synthesize TBB/TBH instructions to make use of compressed jump tables

This is crashing in some cases.  IR attached.

The crash is here:

      MachineInstr *Shift = User.MI->getPrevNode();
       if (Shift->getOpcode() != ARM::tLSLri ||
           Shift->getOperand(3).getImm() != 2 ||
           !Shift->getOperand(2).isKill())
         continue;

I think the problem is that you're incorrectly assuming that tLEApcrelJT 
isn't the first instruction in a basic block.

-Eli

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
target triple = "thumbv5e-none-linux-gnueabi"

%struct.MACROBLOCK.1.8.15.22.29.36.43.50.57.64.78.120.134 = type { [4 x %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133], [6 x [15 x i16]], [6 x i32], i32, i32, i32, i32, i32, i32, %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133, [4 x %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133], [4 x %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133], [4 x i32], i32, i32, i32, [4 x %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133], [4 x %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133], i32, %struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133, i32 }
%struct.VECTOR.0.7.14.21.28.35.42.49.56.63.77.119.133 = type { i32, i32 }

define void @predict_acdc(%struct.MACROBLOCK.1.8.15.22.29.36.43.50.57.64.78.120.134* %pMBs, i32 %block) {
entry:
  %arrayidx3 = getelementptr inbounds %struct.MACROBLOCK.1.8.15.22.29.36.43.50.57.64.78.120.134, %struct.MACROBLOCK.1.8.15.22.29.36.43.50.57.64.78.120.134* %pMBs, i32 undef, i32 2, i32 %block
  switch i32 %block, label %sw.epilog [
    i32 0, label %sw.bb
    i32 1, label %sw.bb79
    i32 2, label %sw.bb85
    i32 3, label %sw.bb91
    i32 4, label %sw.bb94
    i32 5, label %sw.bb107
  ]

sw.bb:                                            ; preds = %entry
  unreachable

sw.bb79:                                          ; preds = %entry
  unreachable

sw.bb85:                                          ; preds = %entry
  unreachable

sw.bb91:                                          ; preds = %entry
  unreachable

sw.bb94:                                          ; preds = %entry
  unreachable

sw.bb107:                                         ; preds = %entry
  unreachable

sw.epilog:                                        ; preds = %entry
  store i32 1, i32* %arrayidx3, align 4
  unreachable
}