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configure

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    • Tom Lane's avatar
      5cfa8dd3
      Use mutex hint bit in PPC LWARX instructions, where possible. · 5cfa8dd3
      Tom Lane authored
      The hint bit makes for a small but measurable performance improvement
      in access to contended spinlocks.
      
      On the other hand, some PPC chips give an illegal-instruction failure.
      There doesn't seem to be a completely bulletproof way to tell whether the
      hint bit will cause an illegal-instruction failure other than by trying
      it; but most if not all 64-bit PPC machines should accept it, so follow
      the Linux kernel's lead and assume it's okay to use it in 64-bit builds.
      Of course we must also check whether the assembler accepts the command,
      since even with a recent CPU the toolchain could be old.
      
      Patch by Manabu Ori, significantly modified by me.
      5cfa8dd3
      History
      Use mutex hint bit in PPC LWARX instructions, where possible.
      Tom Lane authored
      The hint bit makes for a small but measurable performance improvement
      in access to contended spinlocks.
      
      On the other hand, some PPC chips give an illegal-instruction failure.
      There doesn't seem to be a completely bulletproof way to tell whether the
      hint bit will cause an illegal-instruction failure other than by trying
      it; but most if not all 64-bit PPC machines should accept it, so follow
      the Linux kernel's lead and assume it's okay to use it in 64-bit builds.
      Of course we must also check whether the assembler accepts the command,
      since even with a recent CPU the toolchain could be old.
      
      Patch by Manabu Ori, significantly modified by me.