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| author | Richard Biener <rguenther@suse.de> | 2021-01-13 09:43:52 +0100 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2021-01-13 11:13:33 +0100 |
| commit | ffd28c265e6d611983cd27e9332dc799039a3f04 (patch) | |
| tree | c4cc185c351fc1a6805b62c9ea3740ce1835b876 /gcc/tree-ssa-sccvn.c | |
| parent | 5d057bfeff70e5b8d00e521844c476f62d51e22c (diff) | |
| download | gcc-ffd28c265e6d611983cd27e9332dc799039a3f04.zip gcc-ffd28c265e6d611983cd27e9332dc799039a3f04.tar.gz gcc-ffd28c265e6d611983cd27e9332dc799039a3f04.tar.bz2 | |
tree-optimization/98640 - fix bogus sign-extension with VN
VN tried to express a sign extension from int to long of
a trucated quantity with a plain conversion but that loses the
truncation. Since there's no single operand doing truncate plus
sign extend (there was a proposed SEXT_EXPR to do that at some
point mapping to RTL sign_extract) don't bother to appropriately
model this with two ops (which the VN insert machinery doesn't
handle and which is unlikely to CSE fully).
2021-01-13 Richard Biener <rguenther@suse.de>
PR tree-optimization/98640
* tree-ssa-sccvn.c (visit_nary_op): Do not try to
handle plus or minus from a truncated operand to be
sign-extended.
* gcc.dg/torture/pr98640.c: New testcase.
Diffstat (limited to 'gcc/tree-ssa-sccvn.c')
| -rw-r--r-- | gcc/tree-ssa-sccvn.c | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c index 0ba846f..588f1b8 100644 --- a/gcc/tree-ssa-sccvn.c +++ b/gcc/tree-ssa-sccvn.c @@ -4681,7 +4681,7 @@ visit_copy (tree lhs, tree rhs) is the same. */ static tree -valueized_wider_op (tree wide_type, tree op) +valueized_wider_op (tree wide_type, tree op, bool allow_truncate) { if (TREE_CODE (op) == SSA_NAME) op = vn_valueize (op); @@ -4695,7 +4695,7 @@ valueized_wider_op (tree wide_type, tree op) return tem; /* Or the op is truncated from some existing value. */ - if (TREE_CODE (op) == SSA_NAME) + if (allow_truncate && TREE_CODE (op) == SSA_NAME) { gimple *def = SSA_NAME_DEF_STMT (op); if (is_gimple_assign (def) @@ -4760,12 +4760,15 @@ visit_nary_op (tree lhs, gassign *stmt) || gimple_assign_rhs_code (def) == MULT_EXPR)) { tree ops[3] = {}; + /* When requiring a sign-extension we cannot model a + previous truncation with a single op so don't bother. */ + bool allow_truncate = TYPE_UNSIGNED (TREE_TYPE (rhs1)); /* Either we have the op widened available. */ - ops[0] = valueized_wider_op (type, - gimple_assign_rhs1 (def)); + ops[0] = valueized_wider_op (type, gimple_assign_rhs1 (def), + allow_truncate); if (ops[0]) - ops[1] = valueized_wider_op (type, - gimple_assign_rhs2 (def)); + ops[1] = valueized_wider_op (type, gimple_assign_rhs2 (def), + allow_truncate); if (ops[0] && ops[1]) { ops[0] = vn_nary_op_lookup_pieces |