[Bug target/68785] New: [6 Regression] valgrind reports issues with folding on x86_64

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68785

            Bug ID: 68785
           Summary: [6 Regression] valgrind reports issues with folding on
                    x86_64
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: trippels at gcc dot gnu.org
  Target Milestone: ---
              Host: x86_64-unknown-linux-gnu
            Target: x86_64-unknown-linux-gnu
             Build: x86_64-unknown-linux-gnu

I configured gcc with --enable-valgrind-annotations and built the 
Linux kernel under valgrind on a compile farm machine on x86_64.

The following issue popped up a few times:

==40045== Conditional jump or move depends on uninitialised value(s)
==40045==    at 0xD6F632: get_int_cst_ext_nunits(tree_node*,
generic_wide_int<wide_int_storage> const&) (wide-int.h:795)
==40045==    by 0xD90B52: wide_int_to_tree(tree_node*,
generic_wide_int<wide_int_ref_storage<false> > const&) (tree.c:1432)
==40045==    by 0x808EB4: native_interpret_expr(tree_node*, unsigned char
const*, int) (fold-const.c:7305)
==40045==    by 0x871C03: fold_ctor_reference(tree_node*, tree_node*, unsigned
long, unsigned long, tree_node*) (gimple-fold.c:5500)
==40045==    by 0x8721C9: fold_const_aggregate_ref_1(tree_node*, tree_node*
(*)(tree_node*)) (gimple-fold.c:5616)
==40045==    by 0x87311F: gimple_fold_stmt_to_constant_1(gimple*, tree_node*
(*)(tree_node*), tree_node* (*)(tree_node*)) (gimple-fold.c:5095)
==40045==    by 0xBEE645: evaluate_stmt(gimple*) (tree-ssa-ccp.c:1214)
==40045==    by 0xBEFA0A: visit_assignment(gimple*, tree_node**)
(tree-ssa-ccp.c:2290)
==40045==    by 0xBEFAD7: ccp_visit_stmt(gimple*, edge_def**, tree_node**)
(tree-ssa-ccp.c:2368)
==40045==    by 0xC7E82C: simulate_stmt(gimple*) (tree-ssa-propagate.c:331)
==40045==    by 0xC80385: ssa_propagate(ssa_prop_result (*)(gimple*,
edge_def**, tree_node**), ssa_prop_result (*)(gphi*))
(tree-ssa-propagate.c:509)
==40045==    by 0xBE83E4: (anonymous namespace)::pass_ccp::execute(function*)
(tree-ssa-ccp.c:2408)
==40045== 
==40045== Conditional jump or move depends on uninitialised value(s)
==40045==    at 0xD90EEB: wide_int_to_tree(tree_node*,
generic_wide_int<wide_int_ref_storage<false> > const&) (tree.c:1473)
==40045==    by 0x808EB4: native_interpret_expr(tree_node*, unsigned char
const*, int) (fold-const.c:7305)
==40045==    by 0x871C03: fold_ctor_reference(tree_node*, tree_node*, unsigned
long, unsigned long, tree_node*) (gimple-fold.c:5500)
==40045==    by 0x8721C9: fold_const_aggregate_ref_1(tree_node*, tree_node*
(*)(tree_node*)) (gimple-fold.c:5616)
==40045==    by 0x87311F: gimple_fold_stmt_to_constant_1(gimple*, tree_node*
(*)(tree_node*), tree_node* (*)(tree_node*)) (gimple-fold.c:5095)
==40045==    by 0xBEE645: evaluate_stmt(gimple*) (tree-ssa-ccp.c:1214)
==40045==    by 0xBEFA0A: visit_assignment(gimple*, tree_node**)
(tree-ssa-ccp.c:2290)
==40045==    by 0xBEFAD7: ccp_visit_stmt(gimple*, edge_def**, tree_node**)
(tree-ssa-ccp.c:2368)
==40045==    by 0xC7E82C: simulate_stmt(gimple*) (tree-ssa-propagate.c:331)
==40045==    by 0xC80385: ssa_propagate(ssa_prop_result (*)(gimple*,
edge_def**, tree_node**), ssa_prop_result (*)(gphi*))
(tree-ssa-propagate.c:509)
==40045==    by 0xBE83E4: (anonymous namespace)::pass_ccp::execute(function*)
(tree-ssa-ccp.c:2408)
==40045==    by 0xA10CAC: execute_one_pass(opt_pass*) (passes.c:2336)
==40045== 
==40045== Conditional jump or move depends on uninitialised value(s)
==40045==    at 0xD90E67: wide_int_to_tree(tree_node*,
generic_wide_int<wide_int_ref_storage<false> > const&) (tree.c:1492)
==40045==    by 0x808EB4: native_interpret_expr(tree_node*, unsigned char
const*, int) (fold-const.c:7305)
==40045==    by 0x871C03: fold_ctor_reference(tree_node*, tree_node*, unsigned
long, unsigned long, tree_node*) (gimple-fold.c:5500)
==40045==    by 0x8721C9: fold_const_aggregate_ref_1(tree_node*, tree_node*
(*)(tree_node*)) (gimple-fold.c:5616)
==40045==    by 0x87311F: gimple_fold_stmt_to_constant_1(gimple*, tree_node*
(*)(tree_node*), tree_node* (*)(tree_node*)) (gimple-fold.c:5095)
==40045==    by 0xBEE645: evaluate_stmt(gimple*) (tree-ssa-ccp.c:1214)
==40045==    by 0xBEFA0A: visit_assignment(gimple*, tree_node**)
(tree-ssa-ccp.c:2290)
==40045==    by 0xBEFAD7: ccp_visit_stmt(gimple*, edge_def**, tree_node**)
(tree-ssa-ccp.c:2368)
==40045==    by 0xC7E82C: simulate_stmt(gimple*) (tree-ssa-propagate.c:331)
==40045==    by 0xC80385: ssa_propagate(ssa_prop_result (*)(gimple*,
edge_def**, tree_node**), ssa_prop_result (*)(gphi*))
(tree-ssa-propagate.c:509)
==40045==    by 0xBE83E4: (anonymous namespace)::pass_ccp::execute(function*)
(tree-ssa-ccp.c:2408)
==40045==    by 0xA10CAC: execute_one_pass(opt_pass*) (passes.c:2336)
==40045== 
==40045== Conditional jump or move depends on uninitialised value(s)
==40045==    at 0xD90D13: wide_int_to_tree(tree_node*,
generic_wide_int<wide_int_ref_storage<false> > const&) (tree.h:3217)
==40045==    by 0x808EB4: native_interpret_expr(tree_node*, unsigned char
const*, int) (fold-const.c:7305)
==40045==    by 0x871C03: fold_ctor_reference(tree_node*, tree_node*, unsigned
long, unsigned long, tree_node*) (gimple-fold.c:5500)
==40045==    by 0x8721C9: fold_const_aggregate_ref_1(tree_node*, tree_node*
(*)(tree_node*)) (gimple-fold.c:5616)
==40045==    by 0x87311F: gimple_fold_stmt_to_constant_1(gimple*, tree_node*
(*)(tree_node*), tree_node* (*)(tree_node*)) (gimple-fold.c:5095)
==40045==    by 0xBEE645: evaluate_stmt(gimple*) (tree-ssa-ccp.c:1214)
==40045==    by 0xBEFA0A: visit_assignment(gimple*, tree_node**)
(tree-ssa-ccp.c:2290)
==40045==    by 0xBEFAD7: ccp_visit_stmt(gimple*, edge_def**, tree_node**)
(tree-ssa-ccp.c:2368)
==40045==    by 0xC7E82C: simulate_stmt(gimple*) (tree-ssa-propagate.c:331)
==40045==    by 0xC80385: ssa_propagate(ssa_prop_result (*)(gimple*,
edge_def**, tree_node**), ssa_prop_result (*)(gphi*))
(tree-ssa-propagate.c:509)
==40045==    by 0xBE83E4: (anonymous namespace)::pass_ccp::execute(function*)
(tree-ssa-ccp.c:2408)
==40045==    by 0xA10CAC: execute_one_pass(opt_pass*) (passes.c:2336)
==40045== 
==40045== Use of uninitialised value of size 8
==40045==    at 0xD90D1C: wide_int_to_tree(tree_node*,
generic_wide_int<wide_int_ref_storage<false> > const&) (tree.c:1501)
==40045==    by 0x808EB4: native_interpret_expr(tree_node*, unsigned char
const*, int) (fold-const.c:7305)
==40045==    by 0x871C03: fold_ctor_reference(tree_node*, tree_node*, unsigned
long, unsigned long, tree_node*) (gimple-fold.c:5500)
==40045==    by 0x8721C9: fold_const_aggregate_ref_1(tree_node*, tree_node*
(*)(tree_node*)) (gimple-fold.c:5616)
==40045==    by 0x87311F: gimple_fold_stmt_to_constant_1(gimple*, tree_node*
(*)(tree_node*), tree_node* (*)(tree_node*)) (gimple-fold.c:5095)
==40045==    by 0xBEE645: evaluate_stmt(gimple*) (tree-ssa-ccp.c:1214)
==40045==    by 0xBEFA0A: visit_assignment(gimple*, tree_node**)
(tree-ssa-ccp.c:2290)
==40045==    by 0xBEFAD7: ccp_visit_stmt(gimple*, edge_def**, tree_node**)
(tree-ssa-ccp.c:2368)
==40045==    by 0xC7E82C: simulate_stmt(gimple*) (tree-ssa-propagate.c:331)
==40045==    by 0xC80385: ssa_propagate(ssa_prop_result (*)(gimple*,
edge_def**, tree_node**), ssa_prop_result (*)(gphi*))
(tree-ssa-propagate.c:509)
==40045==    by 0xBE83E4: (anonymous namespace)::pass_ccp::execute(function*)
(tree-ssa-ccp.c:2408)
==40045==    by 0xA10CAC: execute_one_pass(opt_pass*) (passes.c:2336)
==40045== 
==40045== Conditional jump or move depends on uninitialised value(s)
==40045==    at 0xD90D68: wide_int_to_tree(tree_node*,
generic_wide_int<wide_int_ref_storage<false> > const&) (tree.c:1504)
==40045==    by 0x808EB4: native_interpret_expr(tree_node*, unsigned char
const*, int) (fold-const.c:7305)
==40045==    by 0x871C03: fold_ctor_reference(tree_node*, tree_node*, unsigned
long, unsigned long, tree_node*) (gimple-fold.c:5500)
==40045==    by 0x8721C9: fold_const_aggregate_ref_1(tree_node*, tree_node*
(*)(tree_node*)) (gimple-fold.c:5616)
==40045==    by 0x87311F: gimple_fold_stmt_to_constant_1(gimple*, tree_node*
(*)(tree_node*), tree_node* (*)(tree_node*)) (gimple-fold.c:5095)
==40045==    by 0xBEE645: evaluate_stmt(gimple*) (tree-ssa-ccp.c:1214)
==40045==    by 0xBEFA0A: visit_assignment(gimple*, tree_node**)
(tree-ssa-ccp.c:2290)
==40045==    by 0xBEFAD7: ccp_visit_stmt(gimple*, edge_def**, tree_node**)
(tree-ssa-ccp.c:2368)
==40045==    by 0xC7E82C: simulate_stmt(gimple*) (tree-ssa-propagate.c:331)
==40045==    by 0xC80385: ssa_propagate(ssa_prop_result (*)(gimple*,
edge_def**, tree_node**), ssa_prop_result (*)(gphi*))
(tree-ssa-propagate.c:509)
==40045==    by 0xBE83E4: (anonymous namespace)::pass_ccp::execute(function*)
(tree-ssa-ccp.c:2408)
==40045==    by 0xA10CAC: execute_one_pass(opt_pass*) (passes.c:2336)
==40045==