[Bug tree-optimization/106476] New: ICE generating FOLD_EXTRACT_LAST
ams at gcc dot gnu.org
gcc-bugzilla@gcc.gnu.org
Fri Jul 29 13:08:51 GMT 2022
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106476
Bug ID: 106476
Summary: ICE generating FOLD_EXTRACT_LAST
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: ams at gcc dot gnu.org
CC: rguenther at suse dot de
Target Milestone: ---
Target: amdgcn-amdhsa
Commit 8f4d9c1deda "amdgcn: 64-bit not" exposed an ICE in tree-vect_stmts.cc
when compiling gcc.dg/torture/pr67470.c at -O2 for amdgcn. The newly
implemented op is not the problem, but it allows this optimization (and many
others) to proceed, and the error is no longer hidden.
amdgcn has masked vectors and fold_extract_last, which leads to a code path
through tree-vect-stmts.cc that has
vec_then_clause = vec_oprnds2[i];
if (reduction_type != EXTRACT_LAST_REDUCTION)
vec_else_clause = vec_oprnds3[i];
and then
/* Instead of doing ~x ? y : z do x ? z : y. */
vec_compare = new_temp;
std::swap (vec_then_clause, vec_else_clause);
and finally
new_stmt = gimple_build_call_internal
(IFN_FOLD_EXTRACT_LAST, 3, else_clause, vec_compare,
vec_then_clause);
in which vec_then_clause remains set to NULL_TREE.
The dump shows
e_lsm.16_32 = .FOLD_EXTRACT_LAST (e_lsm.16_8, _70, );
(note the last field is missing.)
I can fix the ICE if I add "else vec_else_clause = integer_zero_node", but I'm
not sure that is the correct logical solution.
(CC Richi who touched this code last)
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