Commit ce25e1a7 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r279647: 

------------------------------------------------------------------------
r279647 | sanjoy | 2016-08-24 11:10:21 -0700 (Wed, 24 Aug 2016) | 5 lines

[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.
------------------------------------------------------------------------

llvm-svn: 279689
parent 08064c20

llvm/lib/Transforms/Scalar/SCCP.cpp

+6 −17
Original line number Diff line number Diff line
@@ -1538,17 +1538,6 @@ static bool tryToReplaceWithConstant(SCCPSolver &Solver, Value *V) { 
  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.

//
@@ -1597,8 +1586,9 @@ static bool runSCCP(Function &F, const DataLayout &DL, 
      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;
@@ -1789,10 +1779,9 @@ static bool runIPSCCP(Module &M, const DataLayout &DL, 
        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;

llvm/test/Transforms/SCCP/calltest.ll

+15 −5
Original line number Diff line number Diff line 
; 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

}