[llvm-commits] [llvm] r168970 - in /llvm/trunk: lib/Transforms/Utils/SimplifyCFG.cpp test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll

[Matt Beaumont-Gay]

Hi Evan,

With this change, we're seeing stage2/stage3 differences in our
bootstrap build. I haven't looked at it in detail, but I wanted to
give everybody a heads-up.

-Matt

On Thu, Nov 29, 2012 at 6:02 PM, Evan Cheng <evan.cheng at apple.com> wrote:
> Author: evancheng
> Date: Thu Nov 29 20:02:42 2012
> New Revision: 168970
>
> URL: http://llvm.org/viewvc/llvm-project?rev=168970&view=rev
> Log:
> Fix logic to determine whether to turn a switch into a lookup table. When
> the tables cannot fit in registers (i.e. bitmap), do not emit the table
> if it's using an illegal type.
>
> rdar://12779436
>
> Modified:
>     llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
>     llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
>
> Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=168970&r1=168969&r2=168970&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
> +++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Thu Nov 29 20:02:42 2012
> @@ -3511,22 +3511,29 @@
>  static bool ShouldBuildLookupTable(SwitchInst *SI,
>                                     uint64_t TableSize,
>                                     const DataLayout *TD,
> +                                   const TargetTransformInfo *TTI,
>                              const SmallDenseMap<PHINode*, Type*>& ResultTypes) {
>    // The table density should be at least 40%. This is the same criterion as for
>    // jump tables, see SelectionDAGBuilder::handleJTSwitchCase.
>    // FIXME: Find the best cut-off.
>    if (SI->getNumCases() > TableSize || TableSize >= UINT64_MAX / 10)
>      return false; // TableSize overflowed, or mul below might overflow.
> -  if (SI->getNumCases() * 10 >= TableSize * 4)
> -    return true;
>
>    // If each table would fit in a register, we should build it anyway.
> +  bool AllFit = true;
> +  bool HasIllegalType = false;
>    for (SmallDenseMap<PHINode*, Type*>::const_iterator I = ResultTypes.begin(),
>         E = ResultTypes.end(); I != E; ++I) {
> -    if (!SwitchLookupTable::WouldFitInRegister(TD, TableSize, I->second))
> -      return false;
> +    Type *Ty = I->second;
> +    if (!TTI->getScalarTargetTransformInfo()->isTypeLegal(Ty))
> +      HasIllegalType = true;
> +    if (!SwitchLookupTable::WouldFitInRegister(TD, TableSize, Ty)) {
> +      AllFit = false;
> +      break;
> +    }
>    }
> -  return true;
> +
> +  return AllFit || (!HasIllegalType && (SI->getNumCases() * 10 >= TableSize * 4));
>  }
>
>  /// SwitchToLookupTable - If the switch is only used to initialize one or more
> @@ -3607,7 +3614,7 @@
>
>    APInt RangeSpread = MaxCaseVal->getValue() - MinCaseVal->getValue();
>    uint64_t TableSize = RangeSpread.getLimitedValue() + 1;
> -  if (!ShouldBuildLookupTable(SI, TableSize, TD, ResultTypes))
> +  if (!ShouldBuildLookupTable(SI, TableSize, TD, TTI, ResultTypes))
>      return false;
>
>    // Create the BB that does the lookups.
>
> Modified: llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll?rev=168970&r1=168969&r2=168970&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll (original)
> +++ llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll Thu Nov 29 20:02:42 2012
> @@ -777,3 +777,29 @@
>  ; CHECK: switch.lookup:
>  ; CHECK: getelementptr inbounds [5 x i32]* @switch.table6, i32 0, i32 %switch.tableidx
>  }
> +
> +; Don't create a table with illegal type
> +; rdar://12779436
> +define i96 @illegaltype(i32 %c) {
> +entry:
> +  switch i32 %c, label %sw.default [
> +    i32 42, label %return
> +    i32 43, label %sw.bb1
> +    i32 44, label %sw.bb2
> +    i32 45, label %sw.bb3
> +    i32 46, label %sw.bb4
> +  ]
> +
> +sw.bb1: br label %return
> +sw.bb2: br label %return
> +sw.bb3: br label %return
> +sw.bb4: br label %return
> +sw.default: br label %return
> +return:
> +  %retval.0 = phi i96 [ 15, %sw.default ], [ 27, %sw.bb4 ], [ -1, %sw.bb3 ], [ 0, %sw.bb2 ], [ 123, %sw.bb1 ], [ 55, %entry ]
> +  ret i96 %retval.0
> +
> +; CHECK: @illegaltype
> +; CHECK-NOT: @switch.table
> +; CHECK: switch i32 %c
> +}
>
>
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