On 4/20/23 09:56, Jeff Law via Gcc-patches wrote:
On 1/17/23 15:59, Vineet Gupta wrote:This could be useful for library writers who want to write code variants for fast vs. slow unaligned accesses. We distinguish explicit -mstrict-align (1) vs. slow_unaligned_access cpu tune param (2) for even more code divesity. gcc/ChangeLog: * config/riscv-c.cc (riscv_cpu_cpp_builtins): Generate __riscv_strict_align with value 1 or 2. * config/riscv/riscv.cc: Define riscv_user_wants_strict_align. (riscv_option_override) Set riscv_user_wants_strict_align to TARGET_STRICT_ALIGN. * config/riscv/riscv.h: Declare riscv_user_wants_strict_align. gcc/testsuite/ChangeLog: * gcc.target/riscv/attribute.c: Check for __riscv_strict_align=1. * gcc.target/riscv/predef-align-1.c: New test. * gcc.target/riscv/predef-align-2.c: New test. * gcc.target/riscv/predef-align-3.c: New test. * gcc.target/riscv/predef-align-4.c: New test. * gcc.target/riscv/predef-align-5.c: New test. Signed-off-by: Vineet Gupta <vine...@rivosinc.com> --- gcc/config/riscv/riscv-c.cc | 11 +++++++++++ gcc/config/riscv/riscv.cc | 9 +++++++++ gcc/config/riscv/riscv.h | 1 + gcc/testsuite/gcc.target/riscv/attribute-4.c | 9 +++++++++ gcc/testsuite/gcc.target/riscv/predef-align-1.c | 12 ++++++++++++ gcc/testsuite/gcc.target/riscv/predef-align-2.c | 11 +++++++++++ gcc/testsuite/gcc.target/riscv/predef-align-3.c | 15 +++++++++++++++ gcc/testsuite/gcc.target/riscv/predef-align-4.c | 16 ++++++++++++++++ gcc/testsuite/gcc.target/riscv/predef-align-5.c | 16 ++++++++++++++++ 9 files changed, 100 insertions(+) create mode 100644 gcc/testsuite/gcc.target/riscv/predef-align-1.c create mode 100644 gcc/testsuite/gcc.target/riscv/predef-align-2.c create mode 100644 gcc/testsuite/gcc.target/riscv/predef-align-3.c create mode 100644 gcc/testsuite/gcc.target/riscv/predef-align-4.c create mode 100644 gcc/testsuite/gcc.target/riscv/predef-align-5.c diff --git a/gcc/config/riscv/riscv-c.cc b/gcc/config/riscv/riscv-c.cc index 826ae0067bb8..47a396501d74 100644 --- a/gcc/config/riscv/riscv-c.cc +++ b/gcc/config/riscv/riscv-c.cc @@ -102,6 +102,17 @@ riscv_cpu_cpp_builtins (cpp_reader *pfile) } + /* TARGET_STRICT_ALIGN does not cover all cases. */ + if (riscv_slow_unaligned_access_p) + { + /* Explicit -mstruct-align preceedes cpu tune param + slow_unaligned_access=true. */Did you mean "-mstrict-align" above?
Doh sorry yes.
So I don't understand why we're testing "riscv_user_wants_strict_align" instead of TARGET_STRICT_ALIGN here. AFAICT they're equivalent. But maybe there's something subtle I'm missing.+ if (riscv_user_wants_strict_align) + builtin_define_with_int_value ("__riscv_strict_align", 1); + else + builtin_define_with_int_value ("__riscv_strict_align", 2);
The missing part is slightly over-engineered unaligned access signaling in RV gcc frontend IMHO.
Thing is -mno-strict-align can be over-ruled by the cpu tune param slow_unaligned_access=true (and behave as if -mstrict-align was passed) And I wanted the macro to reflect this (for future proofing) by being defined but with different values.
There's some renewed discussion with Kito on [1] so I need to respin this after getting the agreed upon specification in there.
Thx, -Vineet [1] https://github.com/riscv-non-isa/riscv-c-api-doc/issues/32
