[cfe-commits] r147655 - in /cfe/trunk: lib/CodeGen/CGBuiltin.cpp test/CodeGen/no-builtin.c

[Richard Smith]

On Fri, January 6, 2012 12:20, David Chisnall wrote:
> Author: theraven
> Date: Fri Jan  6 06:20:19 2012
> New Revision: 147655
>
>
> URL: http://llvm.org/viewvc/llvm-project?rev=147655&view=rev
> Log:
> If we are compiling with -fno-builtin then don't do constant folding of
> builtins.
>
> This fixes PR11711.
>
>
>
> Added:
> cfe/trunk/test/CodeGen/no-builtin.c Modified:
> cfe/trunk/lib/CodeGen/CGBuiltin.cpp
>
> Modified: cfe/trunk/lib/CodeGen/CGBuiltin.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGBuiltin.cpp?rev=1
> 47655&r1=147654&r2=147655&view=diff
> ==============================================================================
>  --- cfe/trunk/lib/CodeGen/CGBuiltin.cpp (original)
> +++ cfe/trunk/lib/CodeGen/CGBuiltin.cpp Fri Jan  6 06:20:19 2012
> @@ -175,7 +175,8 @@
> unsigned BuiltinID, const CallExpr *E) { // See if we can constant fold this
> builtin.  If so, don't emit it at all. Expr::EvalResult Result;
> -  if (E->EvaluateAsRValue(Result, CGM.getContext()) &&
> +  if (!getContext().getLangOptions().NoBuiltin &&
> +      E->EvaluateAsRValue(Result, CGM.getContext()) &&
> !Result.hasSideEffects()) {
> if (Result.Val.isInt()) return
> RValue::get(llvm::ConstantInt::get(getLLVMContext(),

I don't understand this change. The constant folder doesn't fold any of the
builtins which the bug report complained about other than fabs. And the
constant folder only folds them when they're in the __builtin_ form (which
isn't what the PR was complaining about). And this change doesn't prevent the
same builtins from being folded in other situations where the constant folder
is run.

> Added: cfe/trunk/test/CodeGen/no-builtin.c
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/no-builtin.c?rev=1
> 47655&view=auto
> ==============================================================================
>  --- cfe/trunk/test/CodeGen/no-builtin.c (added)
> +++ cfe/trunk/test/CodeGen/no-builtin.c Fri Jan  6 06:20:19 2012
> @@ -0,0 +1,20 @@
> +// RUN: %clang_cc1 -fno-builtin -emit-llvm %s -o - | FileCheck %s
> +//
> +// Check that -fno-builtin prevents us from constant-folding through builtins
> +// (PR11711)

I cannot reproduce the problem reported in this bug, before or after your change.

> +
> +double
> +cos(double x)
> +{
> +  printf("ok\n");
> +  exit(0);
> +}
> +
> +int
> +main(int argc, char *argv[])
> +{
> +  cos(1); // CHECK: cos
> +  printf("not ok\n");
> +  abort();
> +}
> +

This test passes with or without your change, with or without -fno-builtin.