[cfe-commits] r130163 - in /cfe/trunk: lib/CodeGen/CGBuiltin.cpp test/CodeGen/builtin-expect.c

[Chris Lattner]

On Apr 25, 2011, at 3:30 PM, Fariborz Jahanian wrote:

> Author: fjahanian
> Date: Mon Apr 25 17:30:02 2011
> New Revision: 130163
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=130163&view=rev
> Log:
> Ir-gen the side-effect(s) when __builtin_expect is
> constant-folded. // rdar://9330105

Hi Fariborz,

I don't think that this is the right approach, because other evaluatable expressions can have side effects as well.  Does something like this work:

if (E->Evaluate(Result, CGM.getContext()) &&
    !Result.hasSideEffects()) {
...
    if (Result.Val.isInt())


-Chris

> 
> Modified:
>    cfe/trunk/lib/CodeGen/CGBuiltin.cpp
>    cfe/trunk/test/CodeGen/builtin-expect.c
> 
> Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=130163&r1=130162&r2=130163&view=diff
> ==============================================================================
> --- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Mon Apr 25 17:30:02 2011
> @@ -177,6 +177,15 @@
>   // See if we can constant fold this builtin.  If so, don't emit it at all.
>   Expr::EvalResult Result;
>   if (E->Evaluate(Result, CGM.getContext())) {
> +    // Short circuiting the __builtin_expect on its 1st argument
> +    // must still IR-gen the 1st and 2nd argument's side-effect.
> +    if (BuiltinID == Builtin::BI__builtin_expect) {
> +      if (E->getArg(0)->HasSideEffects(getContext()))
> +        (void)EmitScalarExpr(E->getArg(0));
> +      if (E->getArg(1)->HasSideEffects(getContext()))
> +        (void)EmitScalarExpr(E->getArg(1));
> +    }
> +    
>     if (Result.Val.isInt())
>       return RValue::get(llvm::ConstantInt::get(getLLVMContext(),
>                                                 Result.Val.getInt()));
> 
> Modified: cfe/trunk/test/CodeGen/builtin-expect.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/builtin-expect.c?rev=130163&r1=130162&r2=130163&view=diff
> ==============================================================================
> --- cfe/trunk/test/CodeGen/builtin-expect.c (original)
> +++ cfe/trunk/test/CodeGen/builtin-expect.c Mon Apr 25 17:30:02 2011
> @@ -1,4 +1,4 @@
> -// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
> +// RUN: %clang_cc1 -triple x86_64-unknown-unknown -emit-llvm -o - %s | FileCheck %s
> 
> int x;
> int y(void);
> @@ -9,3 +9,13 @@
>     foo ();
> }
> 
> +// rdar://9330105
> +void isigprocmask(void);
> +long bar();
> +
> +int main() {
> +    (void) __builtin_expect((isigprocmask(), 0), bar());
> +}
> +
> +// CHECK: call void @isigprocmask()
> +// CHECK: [[C:%.*]] = call i64 (...)* @bar()
> 
> 
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