[PATCH] D127871: [RISCV] Optimize 2x SELECT for floating-point types

Thu Jul 7 21:55:18 PDT 2022

liaolucy added a comment.

In D127871#3637493 <https://reviews.llvm.org/D127871#3637493>, @craig.topper wrote:

> I think the expanded branches are emitted in the wrong order. The condition for the last Select_FPR32_Using_CC_GPR needs to be checked first.

Thanks, Craig. I dump all select, The middle three pairs of instructions can be optimized

    %25:fpr32 = Select_FPR32_Using_CC_GPR killed %21:gpr, %24:gpr, 1, %16:fpr32, %23:fpr32
    %26:fpr32 = Select_FPR32_Using_CC_GPR killed %20:gpr, %24:gpr, 1, %16:fpr32, %23:fpr32
    %28:fpr32 = Select_FPR32_Using_CC_GPR killed %8:gpr, %27:gpr, 4, %4:fpr32, killed %26:fpr32

  optimize1 
   1.1 %29:fpr32 = Select_FPR32_Using_CC_GPR killed %7:gpr, %27:gpr, 4, %3:fpr32, killed %25:fpr3
   2.1 %30:fpr32 = Select_FPR32_Using_CC_GPR killed %18:gpr, %24:gpr, 1, %16:fpr32, killed %29:fpr32
  optimize2
   1.2 %31:fpr32 = Select_FPR32_Using_CC_GPR killed %17:gpr, %24:gpr, 1, %16:fpr32, killed %28:fpr32
   2.2 %32:fpr32 = Select_FPR32_Using_CC_GPR killed %14:gpr, %24:gpr, 1, %19:fpr32, killed %31:fpr32
  optimize3
   1.3 %33:fpr32 = Select_FPR32_Using_CC_GPR killed %13:gpr, %24:gpr, 1, %19:fpr32, killed %30:fpr32
   2.3 %34:fpr32 = Select_FPR32_Using_CC_GPR killed %10:gpr, %24:gpr, 0, %1:fpr32, killed %33:fpr32

    %35:fpr32 = Select_FPR32_Using_CC_GPR killed %9:gpr, %24:gpr, 0, %2:fpr32, killed %32:fpr32

I think  we  should check select1-rs2 == select2-rs2, then 1.1 and 2.1 can not be optimized. I will update patch later

Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D127871