[llvm-bugs] [Bug 52475] New: llc crash due to large structure return

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=52475

            Bug ID: 52475
           Summary: llc crash due to large structure return
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Backend: RISC-V
          Assignee: unassignedbugs at nondot.org
          Reporter: tclin914 at gmail.com
                CC: asb at lowrisc.org, llvm-bugs at lists.llvm.org

Testcase:

define <128 x i32> @ret_split_v128i32(<128 x i32>* %x) {
  %v = load <128 x i32>, <128 x i32>* %x
  ret <128 x i32> %v
}

This testcase is extracted from
llvm/test/CodeGen/RISCV/rvv/fixed-vectors-calling-conv.ll

Execution command:

llc -mtriple=riscv64 -mattr=+experimental-v -riscv-v-vector-bits-min=128
-riscv-v-fixed-length-vector-lmul-max=4 -pre-RA-sched=list-burr foo.ll
--disable-machine-cse test.ll

Change schedule policy for pre-RA to list-burr and disable machine-cse.

Execution result:

Use of %2 does not have a corresponding definition on every path:              
                                                                               
                     48r %3:gpr = ADDI %2:gpr, 448                             
                                                                               
                                          LLVM ERROR: Use not jointly dominated
by defs.
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash
backtrace.                                                                     
                          Stack dump:
...

I think this bug is that DemoteRegister copied out in return bb doesn't be
chained with DemoteRegister copied in in entry bb.

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