[RISCV] Shrink uses of coalesced vsetvlis

When we coalesce and delete a vsetvli, we should shrink the LiveInterval of its AVL register now that there is one less use.

This fixes a -verify-machineinstrs assertion in an MIR test case I found while investigating llvm#97264 (comment). I couldn't recreate this at the LLVM IR level, seemingly because RISCVInsertVSETVLI will just avoid inserting extra vsetvlis that don't need coalesced.

Author: lukel97

llvm/lib/Target/RISCV/RISCVInsertVSETVLI.cpp

@@ -1727,6 +1727,10 @@ void RISCVInsertVSETVLI::coalesceVSETVLIs(MachineBasicBlock &MBB) const {
     if (LIS)
       LIS->RemoveMachineInstrFromMaps(*MI);
     MI->eraseFromParent();
+    if (LIS)
+      for (MachineOperand &MO : MI->uses())
+        if (MO.isReg() && MO.getReg().isVirtual())
+          LIS->shrinkToUses(&LIS->getInterval(MO.getReg()));
   }
 }
 

llvm/test/CodeGen/RISCV/rvv/vsetvli-insert.mir

@@ -92,6 +92,10 @@
     ret void
   }
 
+  define void @coalesce_shrink_removed_vsetvlis_uses() {
+    ret void
+  }
+
   declare <vscale x 1 x i64> @llvm.riscv.vadd.nxv1i64.nxv1i64.i64(<vscale x 1 x i64>, <vscale x 1 x i64>, <vscale x 1 x i64>, i64) #1
 
   declare <vscale x 1 x i64> @llvm.riscv.vle.nxv1i64.i64(<vscale x 1 x i64>, ptr nocapture, i64) #4
@@ -576,3 +580,25 @@ body:             |
     $v0 = PseudoVADD_VV_M1 $noreg, $noreg, $noreg, 3, 6, 0
     PseudoRET
 ...
+---
+name: coalesce_shrink_removed_vsetvlis_uses
+tracksRegLiveness: true
+body: |
+  bb.0:
+    liveins: $x10, $v8
+    ; CHECK-LABEL: name: coalesce_shrink_removed_vsetvlis_uses
+    ; CHECK: liveins: $x10, $v8
+    ; CHECK-NEXT: {{  $}}
+    ; CHECK-NEXT: %avl1:gprnox0 = ADDI $x0, 1
+    ; CHECK-NEXT: %avl2:gprnox0 = ADDI $x0, 2
+    ; CHECK-NEXT: dead $x0 = PseudoVSETVLI %avl2, 209 /* e32, m2, ta, ma */, implicit-def $vl, implicit-def $vtype
+    ; CHECK-NEXT: %x:gpr = COPY $x10
+    ; CHECK-NEXT: renamable $v8 = PseudoVMV_S_X undef renamable $v8, %x, 1, 5 /* e32 */, implicit $vl, implicit $vtype
+    ; CHECK-NEXT: PseudoRET implicit $v8
+    %avl1:gprnox0 = ADDI $x0, 1
+    dead $x0 = PseudoVSETVLI %avl1:gprnox0, 209, implicit-def dead $vl, implicit-def dead $vtype
+    %avl2:gprnox0 = ADDI $x0, 2
+    dead $x0 = PseudoVSETVLI %avl2:gprnox0, 209, implicit-def dead $vl, implicit-def dead $vtype
+    %x:gpr = COPY $x10
+    renamable $v8 = PseudoVMV_S_X undef renamable $v8, killed renamable %x, 1, 5
+    PseudoRET implicit $v8