Hello,
Many RISC-V builtins operate in signed integer types but in many cases,
they are better to be unsigned.
There are a few reasons to do that:
1. Being more natural
For bit manipulation operations, the direct input and the result should
have an unsigned type.
e.g. __builtin_bswap16
Both input and output should be (and are) unsigned.
e.g. __builtin_popcount
The input should be (and is) unsigned.
The output is a bit count and is in int (signed integer).
2. In parity with LLVM 17
LLVM made similar changes to this patch set in commit 599421ae36c3
("[RISCV] Use unsigned instead of signed types for Zk* and Zb*
builtins.") by Craig Topper.
Note that shift amount / round number argument types are changed to
unsigned in this LLVM commit, I did the same.
3. Minimum compatibility breakage
This change rarely causes warnings even if both -Wall and -Wextra are
specified. In fact, only applying PATCH 1/2 does not cause any
additional test failures. PATCH 2/2 only contains testsuite changes
(uses correct types as the builtin uses).
But not completely compatible. For instance, we will notice when operating
with for instance C++'s "auto" / "decltype" or overload resolution.
So, I would like to hear your thoughts first.
Note that, the only reason I separated this RFC patch set to two patches
is to demonstrate that no additional warnings occur even if only PATCH 1/2
is applied. If approved or leaves an RFC PATCH, both will be merged.
p.s.
LLVM has another type of different builtin types (with the same name),
scalar cryptography builtins that operate in 32-bit integers, not XLEN-
specific (applies to SHA-256, SM3 and SM4). For those cases, GCC prefers
XLEN-specific integer type but LLVM 17 always prefers uint32_t.
This is a result of LLVM commit 599421ae36c3 ("[RISCV] Re-define sha256,
Zksed, and Zksh intrinsics to use i32 types.").
Because just changing the width causes errors on GCC, even if I change them
to uint32_t, that would be in a different patch set.
Sincerely,
Tsukasa
Tsukasa OI (2):
RISC-V: Make bit manipulation value / round number and shift amount
types for builtins unsigned
RISC-V: Update testsuite for type-changed builtins
gcc/config/riscv/riscv-builtins.cc | 7 +-
gcc/config/riscv/riscv-cmo.def | 16 +--
gcc/config/riscv/riscv-ftypes.def | 24 ++--
gcc/config/riscv/riscv-scalar-crypto.def | 104 +++++++++---------
gcc/testsuite/gcc.target/riscv/zbc32.c | 6 +-
gcc/testsuite/gcc.target/riscv/zbc64.c | 6 +-
gcc/testsuite/gcc.target/riscv/zbkb32.c | 10 +-
gcc/testsuite/gcc.target/riscv/zbkb64.c | 8 +-
gcc/testsuite/gcc.target/riscv/zbkc32.c | 4 +-
gcc/testsuite/gcc.target/riscv/zbkc64.c | 4 +-
gcc/testsuite/gcc.target/riscv/zbkx32.c | 4 +-
gcc/testsuite/gcc.target/riscv/zbkx64.c | 4 +-
gcc/testsuite/gcc.target/riscv/zknd32.c | 4 +-
gcc/testsuite/gcc.target/riscv/zknd64.c | 10 +-
gcc/testsuite/gcc.target/riscv/zkne32.c | 4 +-
gcc/testsuite/gcc.target/riscv/zkne64.c | 8 +-
gcc/testsuite/gcc.target/riscv/zknh-sha256.c | 8 +-
.../gcc.target/riscv/zknh-sha512-32.c | 12 +-
.../gcc.target/riscv/zknh-sha512-64.c | 8 +-
gcc/testsuite/gcc.target/riscv/zksed32.c | 4 +-
gcc/testsuite/gcc.target/riscv/zksed64.c | 4 +-
gcc/testsuite/gcc.target/riscv/zksh32.c | 4 +-
gcc/testsuite/gcc.target/riscv/zksh64.c | 4 +-
23 files changed, 133 insertions(+), 134 deletions(-)
base-commit: af88776caa20342482b11ccb580742a46c621250
--
2.42.0
