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| author | Richard Biener <rguenther@suse.de> | 2020-03-12 14:18:35 +0100 |
|---|---|---|
| committer | Richard Biener <rguenther@suse.de> | 2020-03-12 14:19:36 +0100 |
| commit | 1dc00a8ec9aeba86b74b16bff6f171824bb7b4a1 (patch) | |
| tree | eadb3fa8164c3ad87d25d9a15f97b463e138cef6 /gcc/tree-ssa-sccvn.c | |
| parent | fcc443b97e19d9c8a2d8ccdfa4cc20682165827e (diff) | |
| download | gcc-1dc00a8ec9aeba86b74b16bff6f171824bb7b4a1.zip gcc-1dc00a8ec9aeba86b74b16bff6f171824bb7b4a1.tar.gz gcc-1dc00a8ec9aeba86b74b16bff6f171824bb7b4a1.tar.bz2 | |
tree-optimization/94103 avoid CSE of loads with padding
VN currently replaces a load of a 16 byte entity 128 bits of precision
(TImode) with the result of a load of a 16 byte entity with 80 bits of
mode precision (XFmode). That will go downhill since if the padding
bits are not actually filled with memory contents those bits are
missing.
2020-03-12 Richard Biener <rguenther@suse.de>
PR tree-optimization/94103
* tree-ssa-sccvn.c (visit_reference_op_load): Avoid type
punning when the mode precision is not sufficient.
* gcc.target/i386/pr94103.c: New testcase.
Diffstat (limited to 'gcc/tree-ssa-sccvn.c')
| -rw-r--r-- | gcc/tree-ssa-sccvn.c | 23 |
1 files changed, 16 insertions, 7 deletions
diff --git a/gcc/tree-ssa-sccvn.c b/gcc/tree-ssa-sccvn.c index b7174cd..150ddad 100644 --- a/gcc/tree-ssa-sccvn.c +++ b/gcc/tree-ssa-sccvn.c @@ -4899,13 +4899,22 @@ visit_reference_op_load (tree lhs, tree op, gimple *stmt) if (result && !useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (op))) { - /* We will be setting the value number of lhs to the value number - of VIEW_CONVERT_EXPR <TREE_TYPE (result)> (result). - So first simplify and lookup this expression to see if it - is already available. */ - gimple_match_op res_op (gimple_match_cond::UNCOND, - VIEW_CONVERT_EXPR, TREE_TYPE (op), result); - result = vn_nary_build_or_lookup (&res_op); + /* Avoid the type punning in case the result mode has padding where + the op we lookup has not. */ + if (maybe_lt (GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (result))), + GET_MODE_PRECISION (TYPE_MODE (TREE_TYPE (op))))) + result = NULL_TREE; + else + { + /* We will be setting the value number of lhs to the value number + of VIEW_CONVERT_EXPR <TREE_TYPE (result)> (result). + So first simplify and lookup this expression to see if it + is already available. */ + gimple_match_op res_op (gimple_match_cond::UNCOND, + VIEW_CONVERT_EXPR, TREE_TYPE (op), result); + result = vn_nary_build_or_lookup (&res_op); + } + /* When building the conversion fails avoid inserting the reference again. */ if (!result) |