I figured it's easier to parse this as a series rather than one big patch, in particular since target-specific code is involved.
This adds an else operand to masked-load operations in order to avoid implicit dependencies on zeroed masked-out elements. riscv does not mandate zeroing for those but rather leaves them unspecified. The general idea is to query the proper operand of the target's respective optab for a supported else value. If the supported value is non-zero emit a cond_expr after the load in order to make the dependency explicit and allow it to be optimized with the surrounding code. In order to keep the fallout manageable the patch is, for now, restricted to only emit cond_exprs during explicit masking in tree-ifcvt. I have a local version that emits a vec_cond_expr for each vector mask load but that would cause several ripple effects further down the line. Loop masking in vectorizer context is as before. Also, the patch series only considers element masking else values and no else value for length masking. The backend changes are supposed to be more proof-of-concept than anything and are surely not idiomatic. x86's and aarch64's test suite results are, however, unchanged. Robin Dapp (8): docs: Document maskload else operand and behavior. ifn: Add else-operand handling. tree-ifcvt: Enforce zero else value after maskload. vect: Add maskload else value support. aarch64: Add masked-load else operands. gcn: Add else operand to masked loads. i386: Add else operand to masked loads. RISC-V: Add else operand to masked loads [PR115536]. .../aarch64/aarch64-sve-builtins-base.cc | 58 +++-- gcc/config/aarch64/aarch64-sve-builtins.cc | 5 + gcc/config/aarch64/aarch64-sve-builtins.h | 1 + gcc/config/aarch64/aarch64-sve.md | 47 +++- gcc/config/aarch64/aarch64-sve2.md | 3 +- gcc/config/aarch64/predicates.md | 4 + gcc/config/gcn/gcn-valu.md | 6 +- gcc/config/gcn/predicates.md | 3 + gcc/config/i386/i386-expand.cc | 59 ++++- gcc/config/i386/predicates.md | 15 ++ gcc/config/i386/sse.md | 124 ++++++---- gcc/config/riscv/autovec.md | 45 ++-- gcc/config/riscv/predicates.md | 3 + gcc/config/riscv/riscv-v.cc | 26 ++- gcc/doc/md.texi | 60 +++-- gcc/internal-fn.cc | 88 +++++-- gcc/internal-fn.h | 11 +- gcc/optabs-query.cc | 83 +++++-- gcc/optabs-query.h | 3 +- gcc/optabs-tree.cc | 43 ++-- gcc/optabs-tree.h | 8 +- .../gcc.target/riscv/rvv/autovec/pr115336.c | 20 ++ .../gcc.target/riscv/rvv/autovec/pr116059.c | 9 + gcc/tree-if-conv.cc | 78 +++++-- gcc/tree-vect-data-refs.cc | 39 +++- gcc/tree-vect-patterns.cc | 17 +- gcc/tree-vect-slp.cc | 22 +- gcc/tree-vect-stmts.cc | 218 ++++++++++++++---- gcc/tree-vectorizer.h | 11 +- 29 files changed, 848 insertions(+), 261 deletions(-) create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr115336.c create mode 100644 gcc/testsuite/gcc.target/riscv/rvv/autovec/pr116059.c -- 2.45.2
