[BOLT][RISCV] Add tests for simple CFG transformations

[jobnoorman]

Summary

Depends on D153345

[rafauler]

bolt/test/RISCV/internal-func-reloc.s

12

This is something we might want to ask of binaries that intend to be BOLTed, as BOLT is going to do a lot of things that RISCV is attempting to do with linkers and linker relaxation. This is specially true if BOLT later reorders functions in a way that now requires thunks/stubs insertion to extend the range of branches that got prematurely relaxed by the linker.

[jobnoorman]

bolt/test/RISCV/internal-func-reloc.s

12

My hope is that this won't be necessary, as it goes against the idea of BOLT working on production binaries where linker relaxation will most certainly be enabled for RISC-V.

I have a WIP patch that tries to deal with this (in a nutshell: "unrelax" instructions in BOLT and let JITLink relax them again later, if possible) that I hope to be able to post later this week.

bolt/test/RISCV/internal-func-reloc.s

+/// Check that functions with internal relocations are considered "simple" and
+/// get transformed by BOLT. The tests rely on the "remove-nops" optimization:
+/// if nops got removed from the function, it got transformed by BOLT.
+
+// RUN: %clang %cflags -o %t %s
+// RUN: llvm-bolt -o %t.bolt %t
+// RUN: llvm-objdump -d %t.bolt | FileCheck %s
+
+  .text
+
+  /// These options are only used to make the assembler output easier to predict
+  .option norelax
+  .option norvc
+
+  .globl _start
+  .p2align 1
+// CHECK: <_start>:
+// CHECK-NEXT: j 0x{{.*}} <_start>
+_start:
+  nop
+1:
+  j 1b
+  .size _start, .-_start
+
+  .globl f
+  .p2align 1
+// CHECK: <f>:
+// CHECK-NEXT: auipc a0, 0
+// CHECK-NEXT: addi a0, a0, 12
+f:
+  nop
+1:
+  /// Same as "la a0, g" but more explicit
+  auipc a0, %pcrel_hi(g)
+  addi  a0, a0, %pcrel_lo(1b)
+  ret
+  .size f, .-f
+
+  .globl g
+  .p2align 1
+g:
+  ret
+  .size g, .-g

bolt/test/RISCV/reorder-blocks-reverse.s

+// RUN: %clang %cflags -o %t %s
+// RUN: llvm-bolt --reorder-blocks=reverse -o %t.bolt %t
+// RUN: llvm-objdump -d --no-show-raw-insn %t.bolt | FileCheck %s
+
+  .text
+  .globl _start
+  .p2align 1
+_start:
+  nop
+  beq t0, t1, 1f
+  nop
+  beq t0, t2, 2f
+1:
+  li a0, 5
+  j 3f
+2:
+  li a0, 6
+3:
+  ret
+  .size _start,.-_start
+
+// CHECK: {{.*}}00 <_start>:
+// CHECK-NEXT:   {{.*}}00:       beq t0, t1, {{.*}} <_start+0x10>
+// CHECK-NEXT:   {{.*}}04:       j {{.*}} <_start+0x16>
+// CHECK-NEXT:   {{.*}}08:       ret
+// CHECK-NEXT:   {{.*}}0a:       li a0, 6
+// CHECK-NEXT:   {{.*}}0c:       j {{.*}} <_start+0x8>
+// CHECK-NEXT:   {{.*}}10:       li a0, 5
+// CHECK-NEXT:   {{.*}}12:       j {{.*}} <_start+0x8>
+// CHECK-NEXT:   {{.*}}16:       beq t0, t2, {{.*}} <_start+0xa>
+// CHECK-NEXT:   {{.*}}1a:       j {{.*}} <_start+0x10>