[llvm] r279647 - [SCCP] Don't delete side-effecting instructions

[Davide Italiano via llvm-commits]

Thanks for the quick fix!

On Aug 24, 2016 8:18 PM, "Sanjoy Das via llvm-commits" <
llvm-commits at lists.llvm.org> wrote:

> Author: sanjoy
> Date: Wed Aug 24 13:10:21 2016
> New Revision: 279647
>
> URL: http://llvm.org/viewvc/llvm-project?rev=279647&view=rev
> Log:
> [SCCP] Don't delete side-effecting instructions
>
> I'm not sure if the `!isa<CallInst>(Inst) &&
> !isa<TerminatorInst>(Inst))` bit is correct either, but this fixes the
> case we know is broken.
>
> Modified:
>     llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
>     llvm/trunk/test/Transforms/SCCP/calltest.ll
>
> Modified: llvm/trunk/lib/Transforms/Scalar/SCCP.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/
> Transforms/Scalar/SCCP.cpp?rev=279647&r1=279646&r2=279647&view=diff
> ============================================================
> ==================
> --- llvm/trunk/lib/Transforms/Scalar/SCCP.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/SCCP.cpp Wed Aug 24 13:10:21 2016
> @@ -1559,17 +1559,6 @@ static bool tryToReplaceWithConstant(SCC
>    return true;
>  }
>
> -static bool tryToReplaceInstWithConstant(SCCPSolver &Solver, Instruction
> *Inst,
> -                                         bool shouldEraseFromParent) {
> -  if (!tryToReplaceWithConstant(Solver, Inst))
> -    return false;
> -
> -  // Delete the instruction.
> -  if (shouldEraseFromParent)
> -    Inst->eraseFromParent();
> -  return true;
> -}
> -
>  // runSCCP() - Run the Sparse Conditional Constant Propagation algorithm,
>  // and return true if the function was modified.
>  //
> @@ -1618,8 +1607,9 @@ static bool runSCCP(Function &F, const D
>        if (Inst->getType()->isVoidTy() || isa<TerminatorInst>(Inst))
>          continue;
>
> -      if (tryToReplaceInstWithConstant(Solver, Inst,
> -                                       true /* shouldEraseFromParent */))
> {
> +      if (tryToReplaceWithConstant(Solver, Inst)) {
> +        if (isInstructionTriviallyDead(Inst))
> +          Inst->eraseFromParent();
>          // Hey, we just changed something!
>          MadeChanges = true;
>          ++NumInstRemoved;
> @@ -1823,10 +1813,9 @@ static bool runIPSCCP(Module &M, const D
>          Instruction *Inst = &*BI++;
>          if (Inst->getType()->isVoidTy())
>            continue;
> -        if (tryToReplaceInstWithConstant(
> -                Solver, Inst,
> -                !isa<CallInst>(Inst) &&
> -                    !isa<TerminatorInst>(Inst) /* shouldEraseFromParent
> */)) {
> +        if (tryToReplaceWithConstant(Solver, Inst)) {
> +          if (!isa<CallInst>(Inst) && !isa<TerminatorInst>(Inst))
> +            Inst->eraseFromParent();
>            // Hey, we just changed something!
>            MadeChanges = true;
>            ++IPNumInstRemoved;
>
> Modified: llvm/trunk/test/Transforms/SCCP/calltest.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/
> Transforms/SCCP/calltest.ll?rev=279647&r1=279646&r2=279647&view=diff
> ============================================================
> ==================
> --- llvm/trunk/test/Transforms/SCCP/calltest.ll (original)
> +++ llvm/trunk/test/Transforms/SCCP/calltest.ll Wed Aug 24 13:10:21 2016
> @@ -1,12 +1,16 @@
> -; RUN: opt < %s -sccp -loop-deletion -simplifycfg -S | not grep br
> +; RUN: opt < %s -sccp -loop-deletion -simplifycfg -S | FileCheck %s
>
> +declare double @sqrt(double) readnone nounwind
> +%empty = type {}
> +declare %empty @has_side_effects()
> +
> +define double @test_0(i32 %param) {
> +; CHECK-LABEL: @test_0(
> +; CHECK-NOT: br
> +entry:
>  ; No matter how hard you try, sqrt(1.0) is always 1.0.  This allows the
>  ; optimizer to delete this loop.
>
> -declare double @sqrt(double)
> -
> -define double @test(i32 %param) {
> -entry:
>         br label %Loop
>  Loop:          ; preds = %Loop, %entry
>         %I2 = phi i32 [ 0, %entry ], [ %I3, %Loop ]             ; <i32>
> [#uses=1]
> @@ -19,3 +23,9 @@ Exit:         ; preds = %Loop
>         ret double %V
>  }
>
> +define i32 @test_1() {
> +; CHECK-LABEL: @test_1(
> +; CHECK: call %empty @has_side_effects()
> +  %1 = call %empty @has_side_effects()
> +  ret i32 0
> +}
>
>
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