[llvm-bugs] [Bug 38680] New: The RegisterCoalescer don't propagate undef flag when removing IMPLICIT_DEF

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38680

            Bug ID: 38680
           Summary: The RegisterCoalescer don't propagate undef flag when
                    removing IMPLICIT_DEF
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Register Allocator
          Assignee: unassignedbugs at nondot.org
          Reporter: karl-johan.karlsson at ericsson.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 20760
  --> https://bugs.llvm.org/attachment.cgi?id=20760&action=edit
llc -O0 -mtriple i686-- -o - ./registercoalescer_implicitdef.mir
-run-pass=simple-register-coalescing

$ llc -O0 -mtriple i686-- -o - ./registercoalescer_implicitdef.mir
-run-pass=simple-register-coalescing

# Machine code for function main: NoPHIs, TracksLiveness

bb.0:
  %1:gr32 = ADD32ri8 %1:gr32, 1, implicit-def dead $eflags
  CMP32ri8 %0:gr32, 42, implicit-def $eflags

# End machine code for function main.

*** Bad machine code: Reading virtual register without a def ***
- function:    main
- basic block: %bb.0  (0x6d981f8)
- instruction: CMP32ri8 %0:gr32, 42, implicit-def $eflags
- operand 0:   %0:gr32
LLVM ERROR: Found 1 machine code errors.

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