[RISCV][MISched] Set EnableIntervals to true for SiFive7 (#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 SiFive7VA.

Author: michaelmaitland

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,

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 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  |
+
+...