[RISCV] Do not outline CFI instructions when they are needed in EH

We saw a failure caused by unwinding with incomplete CFIs, so we
can't outline CFI instructions when they are needed in EH.

This is a recommit of 0d40688, which was reverted in ce83883 as
related precommit test 360d44e caused some errors.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D122634

Author: pcwang-thead

llvm/lib/Target/RISCV/RISCVInstrInfo.cpp

@@ -1246,7 +1246,12 @@ RISCVInstrInfo::getOutliningType(MachineBasicBlock::iterator &MBBI,
   if (MI.isPosition()) {
     // We can manually strip out CFI instructions later.
     if (MI.isCFIInstruction())
-      return outliner::InstrType::Invisible;
+      // If current function has exception handling code, we can't outline &
+      // strip these CFI instructions since it may break .eh_frame section
+      // needed in unwinding.
+      return MI.getMF()->getFunction().needsUnwindTableEntry()
+                 ? outliner::InstrType::Illegal
+                 : outliner::InstrType::Invisible;
 
     return outliner::InstrType::Illegal;
   }

llvm/test/CodeGen/RISCV/machine-outliner-throw.ll

@@ -1,11 +1,20 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
 ; RUN: llc -verify-machineinstrs -enable-machine-outliner -mattr=+m -mtriple=riscv64 < %s | FileCheck %s
 
 ; Ensure that we won't outline CFIs when they are needed in unwinding.
 
 define i32 @func1(i32 %x) #0 {
 ; CHECK-LABEL: func1:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    call t0, OUTLINED_FUNCTION_0
+; CHECK-NEXT:    addi sp, sp, -16
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s0, 0(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    .cfi_offset ra, -8
+; CHECK-NEXT:    .cfi_offset s0, -16
+; CHECK-NEXT:    mulw a0, a0, a0
+; CHECK-NEXT:    addiw s0, a0, 1
+; CHECK-NEXT:    li a0, 4
 ; CHECK-NEXT:    call __cxa_allocate_exception@plt
 ; CHECK-NEXT:    sw s0, 0(a0)
 ; CHECK-NEXT:    lui a1, %hi(_ZTIi)
@@ -25,7 +34,15 @@ entry:
 define i32 @func2(i32 %x) #0 {
 ; CHECK-LABEL: func2:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    call t0, OUTLINED_FUNCTION_0
+; CHECK-NEXT:    addi sp, sp, -16
+; CHECK-NEXT:    .cfi_def_cfa_offset 16
+; CHECK-NEXT:    sd ra, 8(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    sd s0, 0(sp) # 8-byte Folded Spill
+; CHECK-NEXT:    .cfi_offset ra, -8
+; CHECK-NEXT:    .cfi_offset s0, -16
+; CHECK-NEXT:    mulw a0, a0, a0
+; CHECK-NEXT:    addiw s0, a0, 1
+; CHECK-NEXT:    li a0, 4
 ; CHECK-NEXT:    call __cxa_allocate_exception@plt
 ; CHECK-NEXT:    sw s0, 0(a0)
 ; CHECK-NEXT:    lui a1, %hi(_ZTIi)
@@ -42,15 +59,6 @@ entry:
   unreachable
 }
 
-; CHECK-LABEL: OUTLINED_FUNCTION_0:
-; CHECK:       # %bb.0:
-; CHECK-NEXT:    addi sp, sp, -16
-; CHECK-NEXT:    sd ra, 8(sp)
-; CHECK-NEXT:    sd s0, 0(sp)
-; CHECK-NEXT:    mulw a0, a0, a0
-; CHECK-NEXT:    addiw s0, a0, 1
-; CHECK-NEXT:    li a0, 4
-
 @_ZTIi = external constant i8*
 declare i8* @__cxa_allocate_exception(i64)
 declare void @__cxa_throw(i8*, i8*, i8*)