From 43356a2548cfde76e164d446cb69004b488c6a71 Mon Sep 17 00:00:00 2001 From: Aurelien Jarno Date: Tue, 19 Mar 2024 21:40:23 +0100 Subject: [PATCH] unscaledcycleclock: remove RISC-V support Starting with Linux 6.6 [1], RDCYCLE is a privileged instruction on RISC-V and can't be used directly from userland. There is a sysctl option to change that as a transition period, but it will eventually disappear. The RDTIME instruction is another less accurate alternative, however its frequency varies from board to board, and there is currently now way to get its frequency from userland [2]. Therefore this patch just removes the code for unscaledcycleclock on RISC-V. Without processor specific implementation, abseil relies on std::chrono::steady_clock::now().time_since_epoch() which is basically a wrapper around clock_gettime (CLOCK_MONOTONIC), which in turns use __vdso_clock_gettime(). On RISC-V this VDSO is just a wrapper around RDTIME correctly scaled to use nanoseconds units. This fixes the testsuite on riscv64, tested on a VisionFive 2 board. [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=cc4c07c89aada16229084eeb93895c95b7eabaa3 [2] https://github.com/abseil/abseil-cpp/pull/1631 --- absl/base/internal/unscaledcycleclock.cc | 12 ------------ absl/base/internal/unscaledcycleclock_config.h | 6 +++--- 2 files changed, 3 insertions(+), 15 deletions(-) diff --git a/absl/base/internal/unscaledcycleclock.cc b/absl/base/internal/unscaledcycleclock.cc index 05e0e7ba5ee..a0bf3a65f7c 100644 --- a/absl/base/internal/unscaledcycleclock.cc +++ b/absl/base/internal/unscaledcycleclock.cc @@ -121,18 +121,6 @@ double UnscaledCycleClock::Frequency() { return aarch64_timer_frequency; } -#elif defined(__riscv) - -int64_t UnscaledCycleClock::Now() { - int64_t virtual_timer_value; - asm volatile("rdcycle %0" : "=r"(virtual_timer_value)); - return virtual_timer_value; -} - -double UnscaledCycleClock::Frequency() { - return base_internal::NominalCPUFrequency(); -} - #elif defined(_M_IX86) || defined(_M_X64) #pragma intrinsic(__rdtsc) diff --git a/absl/base/internal/unscaledcycleclock_config.h b/absl/base/internal/unscaledcycleclock_config.h index 24b324ac99f..a214a443176 100644 --- a/absl/base/internal/unscaledcycleclock_config.h +++ b/absl/base/internal/unscaledcycleclock_config.h @@ -21,8 +21,8 @@ // The following platforms have an implementation of a hardware counter. #if defined(__i386__) || defined(__x86_64__) || defined(__aarch64__) || \ - defined(__powerpc__) || defined(__ppc__) || defined(__riscv) || \ - defined(_M_IX86) || (defined(_M_X64) && !defined(_M_ARM64EC)) + defined(__powerpc__) || defined(__ppc__) || defined(_M_IX86) || \ + (defined(_M_X64) && !defined(_M_ARM64EC)) #define ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION 1 #else #define ABSL_HAVE_UNSCALED_CYCLECLOCK_IMPLEMENTATION 0 @@ -53,7 +53,7 @@ #if ABSL_USE_UNSCALED_CYCLECLOCK // This macro can be used to test if UnscaledCycleClock::Frequency() // is NominalCPUFrequency() on a particular platform. -#if (defined(__i386__) || defined(__x86_64__) || defined(__riscv) || \ +#if (defined(__i386__) || defined(__x86_64__) || \ defined(_M_IX86) || defined(_M_X64)) #define ABSL_INTERNAL_UNSCALED_CYCLECLOCK_FREQUENCY_IS_CPU_FREQUENCY #endif