From 5c211bf969a6ae6b549d0a53daf4c99870c82210 Mon Sep 17 00:00:00 2001 From: Martin Nowack Date: Sun, 30 Aug 2015 01:47:20 +0200 Subject: Fix signed division by constant 1/ -1 Division by constant divisor get optimized using shift and multiplication operations in STP builder. The used method cannot be applied for divisor 1 and -1. In that case use slow path. --- lib/Solver/STPBuilder.cpp | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'lib/Solver') diff --git a/lib/Solver/STPBuilder.cpp b/lib/Solver/STPBuilder.cpp index a5e4c5ad..c2f23c0a 100644 --- a/lib/Solver/STPBuilder.cpp +++ b/lib/Solver/STPBuilder.cpp @@ -382,6 +382,7 @@ ExprHandle STPBuilder::constructUDivByConstant(ExprHandle expr_n, unsigned width * @return n/d without doing explicit division */ ExprHandle STPBuilder::constructSDivByConstant(ExprHandle expr_n, unsigned width, uint64_t d) { + // Refactor using APInt::ms APInt::magic(); assert(width==32 && "can only compute udiv constants for 32-bit division"); // Compute the constants needed to compute n/d for constant d w/o division by d. @@ -673,11 +674,14 @@ ExprHandle STPBuilder::constructActual(ref e, int *width_out) { assert(*width_out!=1 && "uncanonicalized sdiv"); if (ConstantExpr *CE = dyn_cast(de->right)) - if (optimizeDivides) - if (*width_out == 32) //only works for 32-bit division - return constructSDivByConstant( left, *width_out, + if (optimizeDivides) { + llvm::APInt divisor = CE->getAPValue(); + if (divisor != llvm::APInt(CE->getWidth(),1, false /*unsigned*/) && + divisor != llvm::APInt(CE->getWidth(), -1, true /*signed*/)) + if (*width_out == 32) //only works for 32-bit division + return constructSDivByConstant( left, *width_out, CE->getZExtValue(32)); - + } // XXX need to test for proper handling of sign, not sure I // trust STP ExprHandle right = construct(de->right, width_out); -- cgit 1.4.1