[RISCV] Add testcase for outlining leaf descendants (#114450)

Adapted from AArch64/machine-outliner-leaf-descendants.ll 

Towards: #114437

Author: hiraditya

llvm/test/CodeGen/RISCV/machine-outliner-leaf-descendants.ll

@@ -0,0 +1,127 @@
+; This test is mainly for the -outliner-leaf-descendants flag for MachineOutliner.
+;
+; ===================== -outliner-leaf-descendants=false =====================
+; MachineOutliner finds THREE key `OutlinedFunction` and outlines them. They are:
+;   ```
+;     mov     w0, #1
+;     mov     w1, #2
+;     mov     w2, #3
+;     mov     w3, #4
+;     mov     w4, #5
+;     mov     w5, #6 or #7 or #8
+;     b
+;   ```
+; Each has:
+;   - `SequenceSize=28` and `OccurrenceCount=2`
+;   - each Candidate has `CallOverhead=4` and `FrameOverhead=0`
+;   - `NotOutlinedCost=28*2=56` and `OutliningCost=4*2+28+0=36`
+;   - `Benefit=56-36=20` and `Priority=56/36=1.56`
+;
+; ===================== -outliner-leaf-descendants=true =====================
+; MachineOutliner finds a FOURTH key `OutlinedFunction`, which is:
+;   ```
+;   mov     w0, #1
+;   mov     w1, #2
+;   mov     w2, #3
+;   mov     w3, #4
+;   mov     w4, #5
+;   ```
+; This corresponds to an internal node that has ZERO leaf children, but SIX leaf descendants.
+; It has:
+;   - `SequenceSize=20` and `OccurrenceCount=6`
+;   - each Candidate has `CallOverhead=12` and `FrameOverhead=4`
+;   - `NotOutlinedCost=20*6=120` and `OutliningCost=12*6+20+4=96`
+;   - `Benefit=120-96=24` and `Priority=120/96=1.25`
+;
+; The FOURTH `OutlinedFunction` has lower _priority_ compared to the first THREE `OutlinedFunction`.
+; Hence, we use `-outliner-benefit-threshold=22` to check if the FOURTH `OutlinedFunction` is identified.
+
+; RUN: llc %s -enable-machine-outliner=always -outliner-leaf-descendants=false -mattr=+m -mtriple=riscv64 -filetype=obj -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=CHECK-BASELINE
+
+; RUN: llc %s -enable-machine-outliner=always -outliner-leaf-descendants=false -mattr=+m -mtriple=riscv64 -outliner-benefit-threshold=22 -filetype=obj -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=CHECK-NO-CANDIDATE
+
+; RUN: llc %s -enable-machine-outliner=always -outliner-leaf-descendants=false -mattr=+m -mtriple=riscv32 -filetype=obj -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=CHECK-BASELINE
+
+; RUN: llc %s -enable-machine-outliner=always -outliner-leaf-descendants=false -mattr=+m -mtriple=riscv32 -outliner-benefit-threshold=22 -filetype=obj -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=CHECK-NO-CANDIDATE
+
+; RUN: llc %s -enable-machine-outliner=always -outliner-leaf-descendants=true -mattr=+m -mtriple=riscv64 -filetype=obj -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=CHECK-LEAF-DESCENDANTS
+
+; RUN: llc %s -enable-machine-outliner=always -outliner-leaf-descendants=true -mattr=+m -mtriple=riscv64 -outliner-benefit-threshold=22 -filetype=obj -o %t
+; RUN: llvm-objdump -d %t | FileCheck %s --check-prefix=CHECK-LEAF-DESCENDANTS
+
+
+declare i32 @_Z3fooiiii(i32 noundef, i32 noundef, i32 noundef, i32 noundef, i32 noundef, i32 noundef)
+
+define i32 @_Z2f1v() minsize {
+  %1 = tail call i32 @_Z3fooiiii(i32 noundef 1, i32 noundef 2, i32 noundef 3, i32 noundef 4, i32 noundef 5, i32 noundef 6)
+  ret i32 %1
+}
+
+define i32 @_Z2f2v() minsize {
+  %1 = tail call i32 @_Z3fooiiii(i32 noundef 1, i32 noundef 2, i32 noundef 3, i32 noundef 4, i32 noundef 5, i32 noundef 6)
+  ret i32 %1
+}
+
+define i32 @_Z2f3v() minsize {
+  %1 = tail call i32 @_Z3fooiiii(i32 noundef 1, i32 noundef 2, i32 noundef 3, i32 noundef 4, i32 noundef 5, i32 noundef 7)
+  ret i32 %1
+}
+
+define i32 @_Z2f4v() minsize {
+  %1 = tail call i32 @_Z3fooiiii(i32 noundef 1, i32 noundef 2, i32 noundef 3, i32 noundef 4, i32 noundef 5, i32 noundef 7)
+  ret i32 %1
+}
+
+define i32 @_Z2f5v() minsize {
+  %1 = tail call i32 @_Z3fooiiii(i32 noundef 1, i32 noundef 2, i32 noundef 3, i32 noundef 4, i32 noundef 5, i32 noundef 8)
+  ret i32 %1
+}
+
+define i32 @_Z2f6v() minsize {
+  %1 = tail call i32 @_Z3fooiiii(i32 noundef 1, i32 noundef 2, i32 noundef 3, i32 noundef 4, i32 noundef 5, i32 noundef 8)
+  ret i32 %1
+}
+
+; CHECK-BASELINE: <OUTLINED_FUNCTION_0>:
+; CHECK-BASELINE-NEXT: 	li	a0, 0x1
+; CHECK-BASELINE-NEXT:	li	a1, 0x2
+; CHECK-BASELINE-NEXT:	li	a2, 0x3
+; CHECK-BASELINE-NEXT:	li	a3, 0x4
+; CHECK-BASELINE-NEXT:	li	a4, 0x5
+; CHECK-BASELINE-NEXT:	li	a5, 0x6
+; CHECK-BASELINE-NEXT:	jr	t0
+
+; CHECK-BASELINE: <OUTLINED_FUNCTION_1>:
+; CHECK-BASELINE-NEXT:	li	a0, 0x1
+; CHECK-BASELINE-NEXT:	li	a1, 0x2
+; CHECK-BASELINE-NEXT:	li	a2, 0x3
+; CHECK-BASELINE-NEXT:	li	a3, 0x4
+; CHECK-BASELINE-NEXT:	li	a4, 0x5
+; CHECK-BASELINE-NEXT:	li	a5, 0x7
+; CHECK-BASELINE-NEXT:	jr	t0
+
+; CHECK-BASELINE: <OUTLINED_FUNCTION_2>:
+; CHECK-BASELINE-NEXT:	li	a0, 0x1
+; CHECK-BASELINE-NEXT:	li	a1, 0x2
+; CHECK-BASELINE-NEXT:	li	a2, 0x3
+; CHECK-BASELINE-NEXT:	li	a3, 0x4
+; CHECK-BASELINE-NEXT:	li	a4, 0x5
+; CHECK-BASELINE-NEXT:	li	a5, 0x8
+; CHECK-BASELINE-NEXT:	jr	t0
+
+; CHECK-LEAF-DESCENDANTS: <OUTLINED_FUNCTION_0>:
+; CHECK-LEAF-DESCENDANTS-NEXT:	li	a0, 0x1
+; CHECK-LEAF-DESCENDANTS-NEXT:	li	a1, 0x2
+; CHECK-LEAF-DESCENDANTS-NEXT:	li	a2, 0x3
+; CHECK-LEAF-DESCENDANTS-NEXT:	li	a3, 0x4
+; CHECK-LEAF-DESCENDANTS-NEXT:	li	a4, 0x5
+; CHECK-LEAF-DESCENDANTS-NEXT:	jr	t0
+
+; CHECK-LEAF-DESCENDANTS-NOT: <OUTLINED_FUNCTION_1>:
+
+; CHECK-NO-CANDIDATE-NOT: <OUTLINED_FUNCTION_0>: