[llvm] r194676 - Minor extension to llvm.experimental.patchpoint: don't require a call.

[Eric Christopher]

Hi Andy,

This appears to be breaking a lot of bots...

-eric

On Wed, Nov 13, 2013 at 10:54 PM, Andrew Trick <atrick at apple.com> wrote:
> Author: atrick
> Date: Thu Nov 14 00:54:10 2013
> New Revision: 194676
>
> URL: http://llvm.org/viewvc/llvm-project?rev=194676&view=rev
> Log:
> Minor extension to llvm.experimental.patchpoint: don't require a call.
>
> If a null call target is provided, don't emit a dummy call. This
> allows the runtime to reserve as little nop space as it needs without
> the requirement of emitting a call.
>
> Modified:
>     llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
>     llvm/trunk/lib/Target/X86/X86MCInstLower.cpp
>     llvm/trunk/test/CodeGen/X86/patchpoint.ll
>
> Modified: llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp?rev=194676&r1=194675&r2=194676&view=diff
> ==============================================================================
> --- llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp (original)
> +++ llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp Thu Nov 14 00:54:10 2013
> @@ -6826,7 +6826,7 @@ void SelectionDAGBuilder::visitStackmap(
>  /// \brief Lower llvm.experimental.patchpoint directly to its target opcode.
>  void SelectionDAGBuilder::visitPatchpoint(const CallInst &CI) {
>    // void|i64 @llvm.experimental.patchpoint.void|i64(i32 <id>,
> -  //                                                 i32 <numNopBytes>,
> +  //                                                 i32 <numBytes>,
>    //                                                 i8* <target>,
>    //                                                 i32 <numArgs>,
>    //                                                 [Args...],
>
> Modified: llvm/trunk/lib/Target/X86/X86MCInstLower.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86MCInstLower.cpp?rev=194676&r1=194675&r2=194676&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Target/X86/X86MCInstLower.cpp (original)
> +++ llvm/trunk/lib/Target/X86/X86MCInstLower.cpp Thu Nov 14 00:54:10 2013
> @@ -765,6 +765,8 @@ static void LowerSTACKMAP(MCStreamer &Ou
>      OutStreamer.EmitInstruction(MCInstBuilder(X86::NOOP));
>  }
>
> +// Lower a patchpoint of the form:
> +// [<def>], <id>, <numBytes>, <target>, <numArgs>
>  static void LowerPATCHPOINT(MCStreamer &OutStreamer,
>                              X86MCInstLower &MCInstLowering,
>                              StackMaps &SM,
> @@ -813,17 +815,20 @@ static void LowerPATCHPOINT(MCStreamer &
>                      getStackMapEndMOP(MI.operands_begin(), MI.operands_end()),
>                      isAnyRegCC && hasDef);
>
> -  // Emit MOV to materialize the target address and the CALL to target.
> -  // This is encoded with 12-13 bytes, depending on which register is used.
> -  // We conservatively assume that it is 12 bytes and emit in worst case one
> -  // extra NOP byte.
> -  unsigned EncodedBytes = 12;
> -  OutStreamer.EmitInstruction(MCInstBuilder(X86::MOV64ri)
> -                              .addReg(MI.getOperand(ScratchIdx).getReg())
> -                              .addImm(MI.getOperand(StartIdx + 2).getImm()));
> -  OutStreamer.EmitInstruction(MCInstBuilder(X86::CALL64r)
> -                              .addReg(MI.getOperand(ScratchIdx).getReg()));
> -
> +  unsigned EncodedBytes = 0;
> +  int64_t CallTarget = MI.getOperand(StartIdx + 2).getImm();
> +  if (CallTarget) {
> +    // Emit MOV to materialize the target address and the CALL to target.
> +    // This is encoded with 12-13 bytes, depending on which register is used.
> +    // We conservatively assume that it is 12 bytes and emit in worst case one
> +    // extra NOP byte.
> +    EncodedBytes = 12;
> +    OutStreamer.EmitInstruction(MCInstBuilder(X86::MOV64ri)
> +                                .addReg(MI.getOperand(ScratchIdx).getReg())
> +                                .addImm(CallTarget));
> +    OutStreamer.EmitInstruction(MCInstBuilder(X86::CALL64r)
> +                                .addReg(MI.getOperand(ScratchIdx).getReg()));
> +  }
>    // Emit padding.
>    unsigned NumNOPBytes = MI.getOperand(StartIdx + 1).getImm();
>    assert(NumNOPBytes >= EncodedBytes &&
>
> Modified: llvm/trunk/test/CodeGen/X86/patchpoint.ll
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/patchpoint.ll?rev=194676&r1=194675&r2=194676&view=diff
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/patchpoint.ll (original)
> +++ llvm/trunk/test/CodeGen/X86/patchpoint.ll Thu Nov 14 00:54:10 2013
> @@ -79,6 +79,22 @@ entry:
>    ret i64 10
>  }
>
> +; Test small patchpoints that don't emit calls.
> +define void @small_patchpoint_codegen(i64 %p1, i64 %p2, i64 %p3, i64 %p4) {
> +entry:
> +; CHECK-LABEL: small_patchpoint_codegen:
> +; CHECK:      Ltmp
> +; CHECK:      nop
> +; CHECK-NEXT: nop
> +; CHECK-NEXT: nop
> +; CHECK-NEXT: nop
> +; CHECK-NEXT: nop
> +; CHECK-NEXT: popq
> +; CHECK-NEXT: ret
> +  %result = tail call i64 (i32, i32, i8*, i32, ...)* @llvm.experimental.patchpoint.i64(i32 5, i32 5, i8* null, i32 2, i64 %p1, i64 %p2)
> +  ret void
> +}
> +
>  declare void @llvm.experimental.stackmap(i32, i32, ...)
>  declare void @llvm.experimental.patchpoint.void(i32, i32, i8*, i32, ...)
>  declare i64 @llvm.experimental.patchpoint.i64(i32, i32, i8*, i32, ...)
>
>
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