Add initial coverage for invalid instruction costs in LoopRotate

Once extended with a case which requires duplication, will serve as test for crash being fixed in D127131.

llvm/test/Transforms/LoopRotate/RISCV/invalid-cost.ll

@@ -0,0 +1,78 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -loop-rotate -verify-memoryssa < %s | FileCheck %s
+; RUN: opt -S -passes='require<targetir>,require<assumptions>,loop(loop-rotate)' < %s | FileCheck %s
+
+; Demonstrate handling of invalid costs in LoopRotate.  This test uses
+; scalable vectors on RISCV w/o +V to create a situation where a construct
+; can not be lowered, and is thus invalid regardless of what the target
+; does or does not implement in terms of a cost model.
+
+target datalayout = "e-m:e-p:64:64-i64:64-i128:128-n64-S128"
+target triple = "riscv64-unknown-unknown"
+
+define void @valid() nounwind ssp {
+; CHECK-LABEL: @valid(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_COND:%.*]]
+; CHECK:       for.cond:
+; CHECK-NEXT:    [[I_0:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[INC:%.*]], [[FOR_COND]] ]
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[I_0]], 100
+; CHECK-NEXT:    [[INC]] = add nsw i32 [[I_0]], 1
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_COND]], label [[FOR_END:%.*]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %cmp = icmp slt i32 %i.0, 100
+  br i1 %cmp, label %for.body, label %for.end
+
+
+for.body:                                         ; preds = %for.cond
+  %inc = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}
+
+; Despite having an invalid cost, we can rotate this because we don't
+; need to duplicate any instructions or execute them more frequently.
+define void @invalid_no_dup(<vscale x 1 x i8>* %p) nounwind ssp {
+; CHECK-LABEL: @invalid_no_dup(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_BODY:%.*]]
+; CHECK:       for.body:
+; CHECK-NEXT:    [[I_01:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[INC:%.*]], [[FOR_BODY]] ]
+; CHECK-NEXT:    [[A:%.*]] = load <vscale x 1 x i8>, <vscale x 1 x i8>* [[P:%.*]], align 1
+; CHECK-NEXT:    [[B:%.*]] = add <vscale x 1 x i8> [[A]], [[A]]
+; CHECK-NEXT:    store <vscale x 1 x i8> [[B]], <vscale x 1 x i8>* [[P]], align 1
+; CHECK-NEXT:    [[INC]] = add nsw i32 [[I_01]], 1
+; CHECK-NEXT:    [[CMP:%.*]] = icmp slt i32 [[INC]], 100
+; CHECK-NEXT:    br i1 [[CMP]], label [[FOR_BODY]], label [[FOR_END:%.*]]
+; CHECK:       for.end:
+; CHECK-NEXT:    ret void
+;
+entry:
+  br label %for.cond
+
+for.cond:                                         ; preds = %for.body, %entry
+  %i.0 = phi i32 [ 0, %entry ], [ %inc, %for.body ]
+  %cmp = icmp slt i32 %i.0, 100
+  br i1 %cmp, label %for.body, label %for.end
+
+
+for.body:                                         ; preds = %for.cond
+  %a = load <vscale x 1 x i8>, <vscale x 1 x i8>* %p
+  %b = add <vscale x 1 x i8> %a, %a
+  store <vscale x 1 x i8> %b, <vscale x 1 x i8>* %p
+  %inc = add nsw i32 %i.0, 1
+  br label %for.cond
+
+for.end:                                          ; preds = %for.cond
+  ret void
+}
+

llvm/test/Transforms/LoopRotate/RISCV/lit.local.cfg

@@ -0,0 +1,2 @@
+if not 'RISCV' in config.root.targets:
+    config.unsupported = True