[LLVMbugs] [Bug 18890] New: Lowering of atomic ops doesn't reuse registers

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Tue Feb 18 15:50:39 PST 2014


            Bug ID: 18890
           Summary: Lowering of atomic ops doesn't reuse registers
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: joerg at NetBSD.org
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Created attachment 12084
  --> http://llvm.org/bugs/attachment.cgi?id=12084&action=edit
Test case

Compile the attached test program with -O2 for amd64. Observe that the assembly
is not using known zero value of %rax for the xchg, but creating a new register
for that purpose.

Problem applies to other __sync_* builtins as well.

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