[cfe-commits] r76522 - in /cfe/trunk: lib/Analysis/CFG.cpp test/Analysis/dead-stores.c

[Ted Kremenek]

Thanks Mike!

On Jul 20, 2009, at 5:38 PM, Mike Stump wrote:

> Author: mrs
> Date: Mon Jul 20 19:38:52 2009
> New Revision: 76522
>
> URL: http://llvm.org/viewvc/llvm-project?rev=76522&view=rev
> Log:
> Wire up CFG improvements for while when the condition is known.
>
> Modified:
>    cfe/trunk/lib/Analysis/CFG.cpp
>    cfe/trunk/test/Analysis/dead-stores.c
>
> Modified: cfe/trunk/lib/Analysis/CFG.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Analysis/CFG.cpp?rev=76522&r1=76521&r2=76522&view=diff
>
> =
> =
> =
> =
> =
> =
> =
> =
> ======================================================================
> --- cfe/trunk/lib/Analysis/CFG.cpp (original)
> +++ cfe/trunk/lib/Analysis/CFG.cpp Mon Jul 20 19:38:52 2009
> @@ -701,7 +701,7 @@
> }
>
> CFGBlock* CFGBuilder::VisitIfStmt(IfStmt* I) {
> -  // See if this is a known constant first.
> +  // See if this is a known constant.
>   bool KnownTrue = false;
>   bool KnownFalse = false;
>   Expr::EvalResult Result;
> @@ -1102,6 +1102,18 @@
>   // "while" is a control-flow statement.  Thus we stop processing  
> the current
>   // block.
>
> +  // See if this is a known constant.
> +  bool KnownTrue = false;
> +  bool KnownFalse = false;
> +  Expr::EvalResult Result;
> +  if (W->getCond()->Evaluate(Result, *Context)
> +      && Result.Val.isInt()) {
> +    if (Result.Val.getInt().getBoolValue())
> +      KnownTrue = true;
> +    else
> +      KnownFalse = true;
> +  }
> +
>   CFGBlock* LoopSuccessor = NULL;
>
>   if (Block) {
> @@ -1170,13 +1182,21 @@
>         return 0;
>     }
>
> -    // Add the loop body entry as a successor to the condition.
> -    ExitConditionBlock->addSuccessor(BodyBlock);
> +    if (KnownFalse)
> +      ExitConditionBlock->addSuccessor(0);
> +    else {
> +      // Add the loop body entry as a successor to the condition.
> +      ExitConditionBlock->addSuccessor(BodyBlock);
> +    }
>   }
>
> -  // Link up the condition block with the code that follows the  
> loop.  (the
> -  // false branch).
> -  ExitConditionBlock->addSuccessor(LoopSuccessor);
> +  if (KnownTrue)
> +    ExitConditionBlock->addSuccessor(0);
> +  else {
> +    // Link up the condition block with the code that follows the  
> loop.  (the
> +    // false branch).
> +    ExitConditionBlock->addSuccessor(LoopSuccessor);
> +  }
>
>   // There can be no more statements in the condition block since we  
> loop back
>   // to this block.  NULL out Block to force lazy creation of  
> another block.
>
> Modified: cfe/trunk/test/Analysis/dead-stores.c
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/dead-stores.c?rev=76522&r1=76521&r2=76522&view=diff
>
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
> --- cfe/trunk/test/Analysis/dead-stores.c (original)
> +++ cfe/trunk/test/Analysis/dead-stores.c Mon Jul 20 19:38:52 2009
> @@ -199,6 +199,8 @@
>   int y8 = 4;
>   int y9 = 4;
>   int y10 = 4;
> +  int y11 = 4;
> +  int y12 = 4;
>
>   ++x; // expected-warning{{never read}}
>   ++y1;
> @@ -211,6 +213,8 @@
>   ++y8;
>   ++y9;
>   ++y10;
> +  ++y11;
> +  ++y12;
>
>   switch (j) {
>   case 1:
> @@ -265,5 +269,18 @@
>   case 9:
>     (void)(1 || x);
>     (void)y10;
> +    break;
> +  case 10:
> +    while (1) {
> +      (void)y11;
> +    }
> +    (void)x;
> +    break;
> +  case 11:
> +    while (0) {
> +      (void)x;
> +    }
> +    (void)y12;
> +    break;
>   }
> }
>
>
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