From 0fa0fdb764da72f61b2a504345e7e2750658e133 Mon Sep 17 00:00:00 2001 From: Richard Biener Date: Thu, 14 Sep 2017 11:57:08 +0000 Subject: [PATCH] tree-ssa-sccvn.c (visit_phi): Merge undefined values similar to VN_TOP. 2017-09-14 Richard Biener * tree-ssa-sccvn.c (visit_phi): Merge undefined values similar to VN_TOP. * gcc.dg/tree-ssa/ssa-fre-59.c: New testcase. * gcc.dg/uninit-suppress_2.c: Adjust. * gcc.dg/tree-ssa/ssa-sccvn-2.c: Likewise. From-SVN: r252756 --- gcc/ChangeLog | 5 +++ gcc/testsuite/ChangeLog | 6 +++ gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-59.c | 14 +++++++ gcc/testsuite/gcc.dg/tree-ssa/ssa-sccvn-2.c | 2 +- gcc/testsuite/gcc.dg/uninit-suppress_2.c | 2 +- gcc/tree-ssa-sccvn.c | 61 +++++++++++++++++------------ 6 files changed, 63 insertions(+), 27 deletions(-) create mode 100644 gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-59.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 537005b..3925e46 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,8 @@ +2017-09-14 Richard Biener + + * tree-ssa-sccvn.c (visit_phi): Merge undefined values similar + to VN_TOP. + 2017-09-14 Eric Botcazou * dwarf2out.c (dwarf2out_source_line): Remove superfluous test. diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 77dae41..fe3cfa4 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,9 @@ +2017-09-14 Richard Biener + + * gcc.dg/tree-ssa/ssa-fre-59.c: New testcase. + * gcc.dg/uninit-suppress_2.c: Adjust. + * gcc.dg/tree-ssa/ssa-sccvn-2.c: Likewise. + 2017-09-14 Rainer Orth PR tree-optimization/80996 diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-59.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-59.c new file mode 100644 index 0000000..952934b --- /dev/null +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-fre-59.c @@ -0,0 +1,14 @@ +/* { dg-do compile } */ +/* { dg-options "-O -fdump-tree-fre1" } */ + +int i; +int foo (int b) +{ + int j; + i = 1; + if (b) + j = i; + return i - j; +} + +/* { dg-final { scan-tree-dump "return 0;" "fre1" } } */ diff --git a/gcc/testsuite/gcc.dg/tree-ssa/ssa-sccvn-2.c b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sccvn-2.c index 2fe0dc8..ab75825 100644 --- a/gcc/testsuite/gcc.dg/tree-ssa/ssa-sccvn-2.c +++ b/gcc/testsuite/gcc.dg/tree-ssa/ssa-sccvn-2.c @@ -21,4 +21,4 @@ int vnum_test8(int *data) } /* We should eliminate m - n, and set n = n + k into n = m, and set p to 0 */ -/* { dg-final { scan-tree-dump-times "Eliminated: 4" 1 "fre1"} } */ +/* { dg-final { scan-tree-dump-times "Eliminated: 5" 1 "fre1"} } */ diff --git a/gcc/testsuite/gcc.dg/uninit-suppress_2.c b/gcc/testsuite/gcc.dg/uninit-suppress_2.c index a4371ec..af0f192 100644 --- a/gcc/testsuite/gcc.dg/uninit-suppress_2.c +++ b/gcc/testsuite/gcc.dg/uninit-suppress_2.c @@ -1,5 +1,5 @@ /* { dg-do compile } */ -/* { dg-options "-fno-tree-ccp -fno-tree-vrp -O2 -Wuninitialized -Werror=uninitialized -Wno-error=maybe-uninitialized" } */ +/* { dg-options "-fno-tree-ccp -fno-tree-vrp -fno-tree-fre -fno-tree-pre -fno-code-hoisting -O2 -Wuninitialized -Werror=uninitialized -Wno-error=maybe-uninitialized" } */ void blah(); void bar (int); int gflag; diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c index 93342c0..44618da 100644 --- a/gcc/tree-ssa-sccvn.c +++ b/gcc/tree-ssa-sccvn.c @@ -3860,11 +3860,11 @@ visit_reference_op_store (tree lhs, tree op, gimple *stmt) static bool visit_phi (gimple *phi) { - bool changed = false; - tree result; - tree sameval = VN_TOP; - bool allsame = true; + tree result, sameval = VN_TOP, seen_undef = NULL_TREE; unsigned n_executable = 0; + bool allsame = true; + edge_iterator ei; + edge e; /* TODO: We could check for this in init_sccvn, and replace this with a gcc_assert. */ @@ -3873,8 +3873,6 @@ visit_phi (gimple *phi) /* See if all non-TOP arguments have the same value. TOP is equivalent to everything, so we can ignore it. */ - edge_iterator ei; - edge e; FOR_EACH_EDGE (e, ei, gimple_bb (phi)->preds) if (e->flags & EDGE_EXECUTABLE) { @@ -3884,8 +3882,12 @@ visit_phi (gimple *phi) if (TREE_CODE (def) == SSA_NAME) def = SSA_VAL (def); if (def == VN_TOP) - continue; - if (sameval == VN_TOP) + ; + /* Ignore undefined defs for sameval but record one. */ + else if (TREE_CODE (def) == SSA_NAME + && ssa_undefined_value_p (def, false)) + seen_undef = def; + else if (sameval == VN_TOP) sameval = def; else if (!expressions_equal_p (def, sameval)) { @@ -3893,30 +3895,39 @@ visit_phi (gimple *phi) break; } } - - /* If none of the edges was executable or all incoming values are - undefined keep the value-number at VN_TOP. If only a single edge - is exectuable use its value. */ - if (sameval == VN_TOP - || n_executable == 1) - return set_ssa_val_to (PHI_RESULT (phi), sameval); + + /* If none of the edges was executable keep the value-number at VN_TOP, + if only a single edge is exectuable use its value. */ + if (n_executable <= 1) + result = seen_undef ? seen_undef : sameval; + /* If we saw only undefined values create a new undef SSA name to + avoid false equivalences. */ + else if (sameval == VN_TOP) + { + gcc_assert (seen_undef); + result = seen_undef; + } /* First see if it is equivalent to a phi node in this block. We prefer this as it allows IV elimination - see PRs 66502 and 67167. */ - result = vn_phi_lookup (phi); - if (result) - changed = set_ssa_val_to (PHI_RESULT (phi), result); - /* Otherwise all value numbered to the same value, the phi node has that - value. */ - else if (allsame) - changed = set_ssa_val_to (PHI_RESULT (phi), sameval); + else if ((result = vn_phi_lookup (phi))) + ; + /* If all values are the same use that, unless we've seen undefined + values as well and the value isn't constant. + CCP/copyprop have the same restriction to not remove uninit warnings. */ + else if (allsame + && (! seen_undef || is_gimple_min_invariant (sameval))) + result = sameval; else { - vn_phi_insert (phi, PHI_RESULT (phi)); - changed = set_ssa_val_to (PHI_RESULT (phi), PHI_RESULT (phi)); + result = PHI_RESULT (phi); + /* Only insert PHIs that are varying, for constant value numbers + we mess up equivalences otherwise as we are only comparing + the immediate controlling predicates. */ + vn_phi_insert (phi, result); } - return changed; + return set_ssa_val_to (PHI_RESULT (phi), result); } /* Try to simplify RHS using equivalences and constant folding. */ -- 2.7.4