On Tue, 2012-05-15 at 14:17 +0200, Richard Guenther wrote: > This is the first patch to make the generated code for the testcase > in PR53355 better. It teaches VRP about LSHIFT_EXPRs (albeit only > of a very simple form). > > Bootstrapped on x86_64-unknown-linux-gnu, testing in progress.
This appears to have caused http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53385. Thanks, Bill > > Richard. > > 2012-05-15 Richard Guenther <rguent...@suse.de> > > PR tree-optimization/53355 > * tree-vrp.c (extract_range_from_binary_expr_1): Handle LSHIFT_EXPRs > by constants. > > * gcc.dg/tree-ssa/vrp67.c: New testcase. > > Index: gcc/tree-vrp.c > =================================================================== > *** gcc/tree-vrp.c (revision 187503) > --- gcc/tree-vrp.c (working copy) > *************** extract_range_from_binary_expr_1 (value_ > *** 2403,2408 **** > --- 2403,2409 ---- > && code != ROUND_DIV_EXPR > && code != TRUNC_MOD_EXPR > && code != RSHIFT_EXPR > + && code != LSHIFT_EXPR > && code != MIN_EXPR > && code != MAX_EXPR > && code != BIT_AND_EXPR > *************** extract_range_from_binary_expr_1 (value_ > *** 2596,2601 **** > --- 2597,2636 ---- > extract_range_from_multiplicative_op_1 (vr, code, &vr0, &vr1); > return; > } > + else if (code == LSHIFT_EXPR) > + { > + /* If we have a LSHIFT_EXPR with any shift values outside [0..prec-1], > + then drop to VR_VARYING. Outside of this range we get undefined > + behavior from the shift operation. We cannot even trust > + SHIFT_COUNT_TRUNCATED at this stage, because that applies to rtl > + shifts, and the operation at the tree level may be widened. */ > + if (vr1.type != VR_RANGE > + || !value_range_nonnegative_p (&vr1) > + || TREE_CODE (vr1.max) != INTEGER_CST > + || compare_tree_int (vr1.max, TYPE_PRECISION (expr_type) - 1) == 1) > + { > + set_value_range_to_varying (vr); > + return; > + } > + > + /* We can map shifts by constants to MULT_EXPR handling. */ > + if (range_int_cst_singleton_p (&vr1)) > + { > + value_range_t vr1p = { VR_RANGE, NULL_TREE, NULL_TREE, NULL }; > + vr1p.min > + = double_int_to_tree (expr_type, > + double_int_lshift (double_int_one, > + TREE_INT_CST_LOW (vr1.min), > + TYPE_PRECISION (expr_type), > + false)); > + vr1p.max = vr1p.min; > + extract_range_from_multiplicative_op_1 (vr, MULT_EXPR, &vr0, &vr1p); > + return; > + } > + > + set_value_range_to_varying (vr); > + return; > + } > else if (code == TRUNC_DIV_EXPR > || code == FLOOR_DIV_EXPR > || code == CEIL_DIV_EXPR > Index: gcc/testsuite/gcc.dg/tree-ssa/vrp67.c > =================================================================== > *** gcc/testsuite/gcc.dg/tree-ssa/vrp67.c (revision 0) > --- gcc/testsuite/gcc.dg/tree-ssa/vrp67.c (revision 0) > *************** > *** 0 **** > --- 1,38 ---- > + /* { dg-do compile } */ > + /* { dg-options "-O2 -fdump-tree-vrp1" } */ > + > + unsigned foo (unsigned i) > + { > + if (i == 2) > + { > + i = i << 2; > + if (i != 8) > + link_error (); > + } > + return i; > + } > + unsigned bar (unsigned i) > + { > + if (i == 1 << (sizeof (unsigned) * 8 - 1)) > + { > + i = i << 1; > + if (i != 0) > + link_error (); > + } > + return i; > + } > + unsigned baz (unsigned i) > + { > + i = i & 15; > + if (i == 0) > + return 0; > + i = 1000 - i; > + i >>= 1; > + i <<= 1; > + if (i == 0) > + link_error (); > + return i; > + } > + > + /* { dg-final { scan-tree-dump-times "Folding predicate" 3 "vrp1" } } */ > + /* { dg-final { cleanup-tree-dump "vrp1" } } */
