[llvm] r325630 - [MemoryBuiltins] Check nobuiltin status when identifying calls to free.

[Sam Clegg via llvm-commits]

We have some test code on the WebAssembly waterfall the broke as a
result of this.  Perhaps the test is bad but I've distilled to the
following:

```
#include <stdio.h>
#include <stdlib.h>

void* operator new(size_t s) {
  static int n = 1;
  printf("new %zu\n", s);
  return &n;
}

int main() {
  int* foo = new int;
  printf("%p\n", foo);
  return 0;
}
```

Before this change the above program will always print "new ...".
After this change it only prints this O0.  In O1 and O2 the call to
new is elided.  Is this intended?

On Tue, Feb 20, 2018 at 2:00 PM, Benjamin Kramer via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> Author: d0k
> Date: Tue Feb 20 14:00:33 2018
> New Revision: 325630
>
> URL: http://llvm.org/viewvc/llvm-project?rev=325630&view=rev
> Log:
> [MemoryBuiltins] Check nobuiltin status when identifying calls to free.
>
> This is usually not a problem because this code's main purpose is
> eliminating unused new/delete pairs. We got deletes of nullptr or
> nobuiltin deletes of builtin new wrong though.
>
> Modified:
>     llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
>     llvm/trunk/test/Transforms/InstCombine/malloc-free-delete.ll
>
> Modified: llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryBuiltins.cpp?rev=325630&r1=325629&r2=325630&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Analysis/MemoryBuiltins.cpp (original)
> +++ llvm/trunk/lib/Analysis/MemoryBuiltins.cpp Tue Feb 20 14:00:33 2018
> @@ -112,10 +112,9 @@ static const Function *getCalledFunction
>
>    IsNoBuiltin = CS.isNoBuiltin();
>
> -  const Function *Callee = CS.getCalledFunction();
> -  if (!Callee || !Callee->isDeclaration())
> -    return nullptr;
> -  return Callee;
> +  if (const Function *Callee = CS.getCalledFunction())
> +    return Callee;
> +  return nullptr;
>  }
>
>  /// Returns the allocation data for the given value if it's either a call to a
> @@ -350,11 +349,10 @@ const CallInst *llvm::extractCallocCall(
>
>  /// isFreeCall - Returns non-null if the value is a call to the builtin free()
>  const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
> -  const CallInst *CI = dyn_cast<CallInst>(I);
> -  if (!CI || isa<IntrinsicInst>(CI))
> -    return nullptr;
> -  Function *Callee = CI->getCalledFunction();
> -  if (Callee == nullptr)
> +  bool IsNoBuiltinCall;
> +  const Function *Callee =
> +      getCalledFunction(I, /*LookThroughBitCast=*/false, IsNoBuiltinCall);
> +  if (Callee == nullptr || IsNoBuiltinCall)
>      return nullptr;
>
>    StringRef FnName = Callee->getName();
> @@ -400,7 +398,7 @@ const CallInst *llvm::isFreeCall(const V
>    if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
>      return nullptr;
>
> -  return CI;
> +  return dyn_cast<CallInst>(I);
>  }
>
>  //===----------------------------------------------------------------------===//
>
> Modified: llvm/trunk/test/Transforms/InstCombine/malloc-free-delete.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/malloc-free-delete.ll?rev=325630&r1=325629&r2=325630&view=diff
> ==============================================================================
> --- llvm/trunk/test/Transforms/InstCombine/malloc-free-delete.ll (original)
> +++ llvm/trunk/test/Transforms/InstCombine/malloc-free-delete.ll Tue Feb 20 14:00:33 2018
> @@ -146,7 +146,11 @@ lpad.i:
>  }
>
>  declare i8* @_Znwm(i64) nobuiltin
> -declare i8* @_Znwj(i32) nobuiltin
> +define i8* @_Znwj(i32 %n) nobuiltin {
> +  %z = zext i32 %n to i64
> +  call i8* @_Znwm(i64 %z)
> +  ret i8* %m
> +}
>  declare i8* @_Znam(i64) nobuiltin
>  declare i8* @_Znaj(i32) nobuiltin
>  declare void @_ZdlPv(i8*) nobuiltin
> @@ -197,3 +201,19 @@ define void @test9() {
>    call void @"\01??3 at YAXPEAX@Z"(i8* %new_long_long) builtin
>    ret void
>  }
> +
> +define void @test10()  {
> +; CHECK-LABEL: @test10
> +; CHECK: call void @_ZdlPv
> +  call void @_ZdlPv(i8* null)
> +  ret void
> +}
> +
> +define void @test11() {
> +; CHECK-LABEL: @test11
> +; CHECK: call i8* @_Znwm
> +; CHECK: call void @_ZdlPv
> +  %call = call i8* @_Znwm(i64 8) builtin
> +  call void @_ZdlPv(i8* %call)
> +  ret void
> +}
>
>
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