[InstCombine] Fix SimplifyLibCalls erasing an instruction while IC still had references to it

[aemerson]

Summary

InstCombine keeps a worklist and assumes that optimizations don't eraseFromParent() the instruction, which SimplifyLibCalls violates. This change adds a new callback to SimplifyLibCalls to let clients specify their own hander for erasing actions.

[aemerson]

Ping.

[spatel]

include/llvm/Transforms/Utils/SimplifyLibCalls.h

105

This will fail at link time if a client has not provided the function? Isn't it better to just require this param (and the existing RAUW)?

[aemerson]

include/llvm/Transforms/Utils/SimplifyLibCalls.h

105

Yeah I did think it was a bit odd that the default implementation for the RAUW was removed at some point (it was there when the callback was originally added). I'll add them in.

[spatel]

LGTM

include/llvm/Transforms/Utils/SimplifyLibCalls.h

 class LibCallSimplifier {
 private:
   FortifiedLibCallSimplifier FortifiedSimplifier;
   const DataLayout &DL;
   const TargetLibraryInfo *TLI;
   OptimizationRemarkEmitter &ORE;
   bool UnsafeFPShrink;
   function_ref<void(Instruction *, Value *)> Replacer;
+  function_ref<void(Instruction *)> Eraser;
 
   /// Internal wrapper for RAUW that is the default implementation.
   ///
   /// Other users may provide an alternate function with this signature instead
   /// of this one.
   static void replaceAllUsesWithDefault(Instruction *I, Value *With);
 
+  /// Internal wrapper for eraseFromParent that is the default implementation.
+  static void eraseFromParentDefault(Instruction *I);
+
   /// Replace an instruction's uses with a value using our replacer.
   void replaceAllUsesWith(Instruction *I, Value *With);
 
+  /// Erase an instruction from its parent with our eraser.
+  void eraseFromParent(Instruction *I);
+
+  Value *foldMallocMemset(CallInst *Memset, IRBuilder<> &B);
+
 public:
-  LibCallSimplifier(const DataLayout &DL, const TargetLibraryInfo *TLI,
-                    OptimizationRemarkEmitter &ORE,
-                    function_ref<void(Instruction *, Value *)> Replacer =
-                        &replaceAllUsesWithDefault);
+  LibCallSimplifier(
+      const DataLayout &DL, const TargetLibraryInfo *TLI,
+          &replaceAllUsesWithDefault,
+      function_ref<void(Instruction *)> Eraser = &eraseFromParentDefault);
 
   /// optimizeCall - Take the given call instruction and return a more
   /// optimal value to replace the instruction with or 0 if a more
   /// optimal form can't be found.  Note that the returned value may
   /// be equal to the instruction being optimized.  In this case all
   /// other instructions that use the given instruction were modified
   /// and the given instruction is dead.
   /// The call must not be an indirect call.

lib/Transforms/InstCombine/InstCombineCalls.cpp

 }
 
 Instruction *InstCombiner::tryOptimizeCall(CallInst *CI) {
   if (!CI->getCalledFunction()) return nullptr;
 
   auto InstCombineRAUW = [this](Instruction *From, Value *With) {
     replaceInstUsesWith(*From, With);
   };
-  LibCallSimplifier Simplifier(DL, &TLI, ORE, InstCombineRAUW);
+  auto InstCombineErase = [this](Instruction *I) {
+    eraseInstFromFunction(*I);
+  };
+  LibCallSimplifier Simplifier(DL, &TLI, ORE, InstCombineRAUW,
+                               InstCombineErase);
   if (Value *With = Simplifier.optimizeCall(CI)) {
     ++NumSimplified;
     return CI->use_empty() ? CI : replaceInstUsesWith(*CI, With);
   }
 
   return nullptr;
 }
 

lib/Transforms/Utils/SimplifyLibCalls.cpp

 Value *LibCallSimplifier::optimizeMemMove(CallInst *CI, IRBuilder<> &B) {
   // memmove(x, y, n) -> llvm.memmove(align 1 x, align 1 y, n)
   B.CreateMemMove(CI->getArgOperand(0), 1, CI->getArgOperand(1), 1,
                   CI->getArgOperand(2));
   return CI->getArgOperand(0);
 }
 
 /// Fold memset[_chk](malloc(n), 0, n) --> calloc(1, n).
-static Value *foldMallocMemset(CallInst *Memset, IRBuilder<> &B,
-                               const TargetLibraryInfo &TLI) {
+Value *LibCallSimplifier::foldMallocMemset(CallInst *Memset, IRBuilder<> &B) {
   // This has to be a memset of zeros (bzero).
   auto *FillValue = dyn_cast<ConstantInt>(Memset->getArgOperand(1));
   if (!FillValue || FillValue->getZExtValue() != 0)
     return nullptr;
 
   // TODO: We should handle the case where the malloc has more than one use.
   // This is necessary to optimize common patterns such as when the result of
   // the malloc is checked against null or when a memset intrinsic is used in
   // place of a memset library call.
   auto *Malloc = dyn_cast<CallInst>(Memset->getArgOperand(0));
   if (!Malloc || !Malloc->hasOneUse())
     return nullptr;
 
   // Is the inner call really malloc()?
   Function *InnerCallee = Malloc->getCalledFunction();
   if (!InnerCallee)
     return nullptr;
 
   LibFunc Func;
-  if (!TLI.getLibFunc(*InnerCallee, Func) || !TLI.has(Func) ||
+  if (!TLI->getLibFunc(*InnerCallee, Func) || !TLI->has(Func) ||
       Func != LibFunc_malloc)
     return nullptr;
 
   // The memset must cover the same number of bytes that are malloc'd.
   if (Memset->getArgOperand(2) != Malloc->getArgOperand(0))
     return nullptr;
 
   // Replace the malloc with a calloc. We need the data layout to know what the
   // actual size of a 'size_t' parameter is.
   B.SetInsertPoint(Malloc->getParent(), ++Malloc->getIterator());
   const DataLayout &DL = Malloc->getModule()->getDataLayout();
   IntegerType *SizeType = DL.getIntPtrType(B.GetInsertBlock()->getContext());
   Value *Calloc = emitCalloc(ConstantInt::get(SizeType, 1),
                              Malloc->getArgOperand(0), Malloc->getAttributes(),
-                             B, TLI);
+                             B, *TLI);
   if (!Calloc)
     return nullptr;
 
   Malloc->replaceAllUsesWith(Calloc);
-  Malloc->eraseFromParent();
+  eraseFromParent(Malloc);
 
   return Calloc;
 }
 
 Value *LibCallSimplifier::optimizeMemSet(CallInst *CI, IRBuilder<> &B) {
-  if (auto *Calloc = foldMallocMemset(CI, B, *TLI))
+  if (auto *Calloc = foldMallocMemset(CI, B))
     return Calloc;
 
   // memset(p, v, n) -> llvm.memset(align 1 p, v, n)
   Value *Val = B.CreateIntCast(CI->getArgOperand(1), B.getInt8Ty(), false);
   B.CreateMemSet(CI->getArgOperand(0), Val, CI->getArgOperand(2), 1);
   return CI->getArgOperand(0);
 }
 
if (CalleeFn &&
                              FMul, ExpName)
               : emitUnaryFloatFnCall(FMul, ExpName, B, BaseFn->getAttributes());
 
       // Since the new exp{,2}() is different from the original one, dead code
       // elimination cannot be trusted to remove it, since it may have side
       // effects (e.g., errno).  When the only consumer for the original
       // exp{,2}() is pow(), then it has to be explicitly erased.
       BaseFn->replaceAllUsesWith(ExpFn);
-      BaseFn->eraseFromParent();
+      eraseFromParent(BaseFn);
 
       return ExpFn;
     }
   }
 
   // Evaluate special cases related to a constant base.
 
   const APFloat *BaseF;
if (Value *SimplifiedFortifiedCI = FortifiedSimplifier.optimizeCall(CI)) {
     CallInst *SimplifiedCI = dyn_cast<CallInst>(SimplifiedFortifiedCI);
     if (SimplifiedCI && SimplifiedCI->getCalledFunction()) {
       // Use an IR Builder from SimplifiedCI if available instead of CI
       // to guarantee we reach all uses we might replace later on.
       IRBuilder<> TmpBuilder(SimplifiedCI);
       if (Value *V = optimizeStringMemoryLibCall(SimplifiedCI, TmpBuilder)) {
         // If we were able to further simplify, remove the now redundant call.
         SimplifiedCI->replaceAllUsesWith(V);
-        SimplifiedCI->eraseFromParent();
+        eraseFromParent(SimplifiedCI);
         return V;
       }
     }
     return SimplifiedFortifiedCI;
   }
 
   // Then check for known library functions.
   if (TLI->getLibFunc(*Callee, Func) && TLI->has(Func)) {
if (TLI->getLibFunc(*Callee, Func) && TLI->has(Func)) {
     }
   }
   return nullptr;
 }
 
 LibCallSimplifier::LibCallSimplifier(
     const DataLayout &DL, const TargetLibraryInfo *TLI,
     OptimizationRemarkEmitter &ORE,
-    function_ref<void(Instruction *, Value *)> Replacer)
+    function_ref<void(Instruction *, Value *)> Replacer,
+    function_ref<void(Instruction *)> Eraser)
     : FortifiedSimplifier(TLI), DL(DL), TLI(TLI), ORE(ORE),
-      UnsafeFPShrink(false), Replacer(Replacer) {}
+      UnsafeFPShrink(false), Replacer(Replacer), Eraser(Eraser) {}
 
 void LibCallSimplifier::replaceAllUsesWith(Instruction *I, Value *With) {
   // Indirect through the replacer used in this instance.
   Replacer(I, With);
 }
 
+void LibCallSimplifier::eraseFromParent(Instruction *I) {
+  Eraser(I);
+}
+
 // TODO:
 //   Additional cases that we need to add to this file:
 //
 // cbrt:
 //   * cbrt(expN(X))  -> expN(x/3)
 //   * cbrt(sqrt(x))  -> pow(x,1/6)
 //   * cbrt(cbrt(x))  -> pow(x,1/9)
 //

test/Transforms/InstCombine/simplify-libcalls-erased.ll

+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S < %s -instcombine | FileCheck %s
+
+target triple = "x86_64"
+
+define double @pow_exp(double %x, double %y) {
+; CHECK-LABEL: @pow_exp(
+; CHECK-NEXT:    [[MUL:%.*]] = fmul fast double [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT:    [[EXP:%.*]] = call fast double @llvm.exp.f64(double [[MUL]])
+; CHECK-NEXT:    ret double [[EXP]]
+;
+  %A = alloca i1
+  %call = call fast double @exp(double %x) #1
+  %pow = call fast double @llvm.pow.f64(double %call, double %y)
+  %C1 = fcmp ule double %call, %pow
+  store i1 %C1, i1* %A
+  ret double %pow
+}
+
+declare double @exp(double)
+
+declare double @llvm.pow.f64(double, double) #0
+
+attributes #0 = { nounwind readnone speculatable }
+attributes #1 = { nounwind readnone }