search for: getnumiterationsinrange

Hi, I'm using pass ScalarEvolution to analyze the loop trip count on my application. And I found a possible bug in the code, that is in function SCEVAddRecExpr::getNumIterationsInRange(), Line 2905: 2904 // The exit value should be (End+A)/A. 2905 APInt ExitVal = (End + A).udiv(A); 2906 ConstantInt *ExitValue = ConstantInt::get(ExitVal); The divide should be sdiv, right? otherwise, the ExitVal will be zero when A = -1 For example, for (int i = 15; i > 7; --i)...

...mp slt i32 %tmp13, 0 ; <i1> [#uses=1] pass indvars should transform it into a canonical exit condtion EQ or NE, but as scalarevolution returned NonComputedItCount, it failed to do that. In pass ScalarEvolution three algorithms failed to compute the trip count: 1. In SCEVAddRecExpr::getNumIterationsInRange(), as the loop stride is negative, the exit value expression will be zero: (Here A is the stride value) // The exit value should be (End+A)/A. APInt ExitVal = (End + A).udiv(A); ConstantInt *ExitValue = ConstantInt::get(ExitVal); 2. In Line 1953, the switch-case computes the...

...nc = getelementptr i32* %arrayidx5.phi, i32 1 --> {(4 + %a),+,4}<%for.body> Exits: (1020 + %a) Determining loop execution counts for: @add Loop %for.body: backedge-taken count is -2 Loop %for.body: max backedge-taken count is -2 The problem seems to be in SCEVAddRecExpr:getNumIterationsInRange, specifically // If this is an affine expression then we have this situation: // Solve {0,+,A} in Range === Ax in Range // We know that zero is in the range. If A is positive then we know that // the upper value of the range must be the first possible exit value....

...into a canonical exit condtion EQ or >> > NE, but as scalarevolution returned NonComputedItCount, it failed to do >> > that. >> > >> > In pass ScalarEvolution three algorithms failed to compute the trip count: >> > >> > 1. In SCEVAddRecExpr::getNumIterationsInRange(), as the loop stride is >> > negative, the exit value expression will be zero: (Here A is the stride >> > value) >> > >> > // The exit value should be (End+A)/A. >> > APInt ExitVal = (End + A).udiv(A); >> > ConstantInt *E...