[Exegesis][AArch64] Use more generic cycles counter #133376
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Change counter name to more generic one
Update the test according to the change in the code
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@llvm/pr-subscribers-tools-llvm-exegesis @llvm/pr-subscribers-backend-aarch64 Author: None (r-belenov) Changes[Exegesis][AArch64] Use more generic cycles counter Full diff: https://github.com/llvm/llvm-project/pull/133376.diff 2 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AArch64PfmCounters.td b/llvm/lib/Target/AArch64/AArch64PfmCounters.td
index b1d1664e3f1b1..c7132b40ca2fe 100644
--- a/llvm/lib/Target/AArch64/AArch64PfmCounters.td
+++ b/llvm/lib/Target/AArch64/AArch64PfmCounters.td
@@ -10,7 +10,7 @@
//
//===----------------------------------------------------------------------===//
-def CpuCyclesPfmCounter : PfmCounter<"CPU_CYCLES">;
+def CpuCyclesPfmCounter : PfmCounter<"CYCLES">;
def DefaultPfmCounters : ProcPfmCounters {
let CycleCounter = CpuCyclesPfmCounter;
diff --git a/llvm/unittests/tools/llvm-exegesis/AArch64/TargetTest.cpp b/llvm/unittests/tools/llvm-exegesis/AArch64/TargetTest.cpp
index 71675d9f46739..ca5416eef39d5 100644
--- a/llvm/unittests/tools/llvm-exegesis/AArch64/TargetTest.cpp
+++ b/llvm/unittests/tools/llvm-exegesis/AArch64/TargetTest.cpp
@@ -65,7 +65,7 @@ TEST_F(AArch64TargetTest, SetRegToConstant) {
}
TEST_F(AArch64TargetTest, DefaultPfmCounters) {
- const std::string Expected = "CPU_CYCLES";
+ const std::string Expected = "CYCLES";
EXPECT_EQ(ExegesisTarget_->getPfmCounters("").CycleCounter, Expected);
EXPECT_EQ(ExegesisTarget_->getPfmCounters("unknown_cpu").CycleCounter,
Expected);
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@lakshayk-nv (since you aren't in the LLVM org and I can't request your review directly). |
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I'm not sure it is mentioned explicitly. libpfm4 uses PERF_COUNT_HW_CPU_CYCLES for "CYCLES" on all architectures (it's just the counter used for "perf stat -e cycles ..."). It is mapped to ARMV8_PMUV3_PERFCTR_CPU_CYCLES here - https://github.com/torvalds/linux/blob/acb4f33713b9f6cadb6143f211714c343465411c/drivers/perf/arm_pmuv3.c#L45 ; the definition of ARMV8_PMUV3_PERFCTR_CPU_CYCLES is here - https://github.com/torvalds/linux/blob/acb4f33713b9f6cadb6143f211714c343465411c/include/linux/perf/arm_pmuv3.h#L33 |
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Mapping of "CYCLES" to PERF_COUNT_HW_CPU_CYCLES in libpfm4 is done by generic code in pfmlib_parse_event() - https://sourceforge.net/p/perfmon2/libpfm4/ci/master/tree/lib/pfmlib_common.c#l1876 Note that most architectures supported by llvm-exegesis use "CYCLES" currently - see https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/RISCV/RISCVPfmCounters.td , https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/Mips/MipsPfmCounters.td , https://github.com/llvm/llvm-project/blob/main/llvm/lib/Target/PowerPC/PPCPfmCounters.td |
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(Merging since the author does not have commit access). |
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CPU_CYCLES counter does not work on some Aarch64 CPUs; CYCLES is more generic and is equivalent to CPU_CYCLES in case the latter is supported. Longer story - CPU_CYCLES work only on CPU models explicitly recognized by libpfm4 ( via pfm_arm_detect_*() functions in https://sourceforge.net/p/perfmon2/libpfm4/ci/master/tree/lib/pfmlib_arm_armv8.c ) and its name is consistent with ARM documentation. However, the counter is architectural and is supported on all ARMv8 CPUs; libpfm4 recognizes generic PMU on unknown ARMv8 CPUs, but does not provide CPU_CYCLES event. Instead, CYCLES is provided (an alias to PERF_COUNT_HW_CPU_CYCLES). Physically, it is the same event with code 0x11. On supported architectures CYCLES also work, so the change should not introduce regression.
CPU_CYCLES counter does not work on some Aarch64 CPUs; CYCLES is more generic and is equivalent to CPU_CYCLES in case the latter is supported.
Longer story - CPU_CYCLES work only on CPU models explicitly recognized by libpfm4 ( via pfm_arm_detect_*() functions in https://sourceforge.net/p/perfmon2/libpfm4/ci/master/tree/lib/pfmlib_arm_armv8.c ) and its name is consistent with ARM documentation. However, the counter is architectural and is supported on all ARMv8 CPUs; libpfm4 recognizes generic PMU on unknown ARMv8 CPUs, but does not provide CPU_CYCLES event. Instead, CYCLES is provided (an alias to PERF_COUNT_HW_CPU_CYCLES). Physically, it is the same event with code 0x11. On supported architectures CYCLES also work, so the change should not introduce regression.