[llvm] [RISCV][MISched] Set EnableIntervals to true for SiFive7 (PR #75681)
Michael Maitland via llvm-commits
llvm-commits at lists.llvm.org
Fri Dec 15 18:16:07 PST 2023
https://github.com/michaelmaitland created https://github.com/llvm/llvm-project/pull/75681
The SiFive7 scheduler model has been using AcquireAtCycles and ReleaseAtCycles for some time. Without EnableIntervals, the scheduler was not making decisions based on this information. This patch sets EnableIntervals to true, and the test case demonstrates that the VADD instructions can be issued one cycle earlier since the VCQ is not reserved. This leads to better saturation of the VA.
I wonder whether it would be better (in a future patch) to move EnableIntervals out of the scheduler model and add an option like `use-intervals-to-schedule` so that we can control per-program basis. EnableIntervals isn't really a property of the scheduler model itself, and more a property of how the scheduler behaves.
FWIW, I had no idea EnableIntervals existed, and when I added AcquireAtCycles and ReleaseAtCycles, I totally assumed that the scheduler had been using this information out of the box.
>From 63181e77662966f417efde7f08ce93296ac1cf79 Mon Sep 17 00:00:00 2001
From: Michael Maitland <michaeltmaitland at gmail.com>
Date: Fri, 15 Dec 2023 18:05:57 -0800
Subject: [PATCH] [RISCV][MISched] Set EnableIntervals to true for SiFive7
The SiFive7 scheduler model has been using AcquireAtCycles and
ReleaseAtCycles for some time. Without EnableIntervals, the
scheduler was not making decisions based on this information. This patch
sets EnableIntervals to true, and the test case demonstrates that the
VADD instructions can be issued one cycle earlier since the VCQ is not
reserved. This leads to better saturation of the VA.
I wonder whether it would be better (in a future patch) to move EnableIntervals
out of the scheduler model and add an option like `use-intervals-to-schedule`
so that we can control per-program basis. EnableIntervals isn't really a
property of the scheduler model itself, and more a property of how the scheduler
behaves.
FWIW, I had no idea EnableIntervals existed, and when I added
AcquireAtCycles and ReleaseAtCycles, I totally assumed that the
scheduler had been using this information out of the box.
---
llvm/lib/Target/RISCV/RISCVSchedSiFive7.td | 1 +
.../RISCV/sifive7-enable-intervals.mir | 56 +++++++++++++++++++
2 files changed, 57 insertions(+)
create mode 100644 llvm/test/CodeGen/RISCV/sifive7-enable-intervals.mir
diff --git a/llvm/lib/Target/RISCV/RISCVSchedSiFive7.td b/llvm/lib/Target/RISCV/RISCVSchedSiFive7.td
index 45783d482f3bd7..f531ab2fac8f9f 100644
--- a/llvm/lib/Target/RISCV/RISCVSchedSiFive7.td
+++ b/llvm/lib/Target/RISCV/RISCVSchedSiFive7.td
@@ -198,6 +198,7 @@ def SiFive7Model : SchedMachineModel {
let LoadLatency = 3;
let MispredictPenalty = 3;
let CompleteModel = 0;
+ let EnableIntervals = true;
let UnsupportedFeatures = [HasStdExtZbkb, HasStdExtZbkc, HasStdExtZbkx,
HasStdExtZcmt, HasStdExtZknd, HasStdExtZkne,
HasStdExtZknh, HasStdExtZksed, HasStdExtZksh,
diff --git a/llvm/test/CodeGen/RISCV/sifive7-enable-intervals.mir b/llvm/test/CodeGen/RISCV/sifive7-enable-intervals.mir
new file mode 100644
index 00000000000000..20bebc4d2b5f8b
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/sifive7-enable-intervals.mir
@@ -0,0 +1,56 @@
+# RUN: llc -mtriple=riscv64 -mcpu=sifive-x280 -run-pass=machine-scheduler \
+# RUN: -debug-only=machine-scheduler -misched-dump-schedule-trace \
+# RUN: -misched-topdown -o - %s 2>&1 | FileCheck %s
+
+# The purpose of this test is to show that the VADD instructions are issued at
+# so that the SiFive7VA is saturated.
+---
+name: add_m2
+tracksRegLiveness: true
+body: |
+ bb.0.entry:
+ liveins: $v8m2, $v10m2, $v12m2, $v14m2, $x10
+
+ %4:gprnox0 = COPY $x10
+ %3:vrm2 = COPY $v14m2
+ %2:vrm2 = COPY $v12m2
+ %1:vrm2 = COPY $v10m2
+ %0:vrm2 = COPY $v8m2
+ dead $x0 = PseudoVSETVLI %4, 217 /* e64, m2, ta, ma */, implicit-def $vl, implicit-def $vtype
+ %5:vrm2 = PseudoVADD_VV_M2 undef %5, %0, %1, $noreg, 6 /* e64 */, 0 /* tu, mu */, implicit $vl, implicit $vtype
+ %6:vrm2 = PseudoVADD_VV_M2 undef %6, %3, %2, $noreg, 6 /* e64 */, 0 /* tu, mu */, implicit $vl, implicit $vtype
+ %7:vrm2 = PseudoVADD_VV_M2 undef %7, %5, %6, $noreg, 6 /* e64 */, 0 /* tu, mu */, implicit $vl, implicit $vtype
+ $v8m2 = COPY %7
+ PseudoRET implicit $v8m2
+
+# CHECK: *** Final schedule for %bb.0 ***
+# CHECK-NEXT: * Schedule table (TopDown):
+# CHECK-NEXT: i: issue
+# CHECK-NEXT: x: resource booked
+# CHECK-NEXT: Cycle | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 |
+# CHECK-NEXT: SU(0) | i | | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeAB | x | | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SU(1) | i | | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeAB | x | | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SU(2) | | i | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeAB | | x | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SU(3) | | i | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeAB | | x | | | | | | | | | | | | | | | |
+# CHECK-NEXT: SU(4) | | | i | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeAB | | | x | | | | | | | | | | | | | | |
+# CHECK-NEXT: SU(5) | | | i | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeA | | | x | | | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7PipeAB | | | x | | | | | | | | | | | | | | |
+# CHECK-NEXT: SU(7) | | | | | i | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7VCQ | | | | | x | | | | | | | | | | | | |
+# CHECK-NEXT: SiFive7VA | | | | | | x | x | x | x | | | | | | | | |
+# CHECK-NEXT: SU(6) | | | | | | | | | i | | | | | | | | |
+# CHECK-NEXT: SiFive7VCQ | | | | | | | | | x | | | | | | | | |
+# CHECK-NEXT: SiFive7VA | | | | | | | | | | x | x | x | x | | | | |
+# CHECK-NEXT: SU(8) | | | | | | | | | | | | | i | | | | |
+# CHECK-NEXT: SiFive7VCQ | | | | | | | | | | | | | x | | | | |
+# CHECK-NEXT: SiFive7VA | | | | | | | | | | | | | | x | x | x | x |
+# CHECK-NEXT: SU(9) | | | | | | | | | | | | | | | | | i |
+# CHECK-NEXT: SiFive7PipeAB | | | | | | | | | | | | | | | | | x |
+
+...
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