[llvm] r271386 - Adding back-end support to two bit scanning intrinsics

[David Majnemer via llvm-commits]

Why do we need this? We already have generic intrinsics:
http://llvm.org/docs/LangRef.html#llvm-cttz-intrinsic
http://llvm.org/docs/LangRef.html#llvm-ctlz-intrinsic

On Wed, Jun 1, 2016 at 5:20 AM, Michael Zuckerman via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: mzuckerm
> Date: Wed Jun  1 07:02:37 2016
> New Revision: 271386
>
> URL: http://llvm.org/viewvc/llvm-project?rev=271386&view=rev
> Log:
> Adding back-end support to two bit scanning intrinsics
>
> Adding LLVM back-end support to two intrinsics dealing with bit scan:
> _bit_scan_forward and _bit_scan_reverse.
> Their functionality is as described in Intel intrinsics guide:
>
> https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_bit_scan_forward&expand=371,370
>
> https://software.intel.com/sites/landingpage/IntrinsicsGuide/#text=_bit_scan_reverse&expand=371,370
>
> Commit on behalf of Omer Paparo Bivas
>
>
> Differential Revision: http://reviews.llvm.org/D19915
>
>
> Added:
>     llvm/trunk/test/CodeGen/X86/bitscan.ll
> Modified:
>     llvm/trunk/include/llvm/IR/IntrinsicsX86.td
>     llvm/trunk/lib/Target/X86/X86IntrinsicsInfo.h
>
> Modified: llvm/trunk/include/llvm/IR/IntrinsicsX86.td
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/IR/IntrinsicsX86.td?rev=271386&r1=271385&r2=271386&view=diff
>
> ==============================================================================
> --- llvm/trunk/include/llvm/IR/IntrinsicsX86.td (original)
> +++ llvm/trunk/include/llvm/IR/IntrinsicsX86.td Wed Jun  1 07:02:37 2016
> @@ -8442,3 +8442,13 @@ let TargetPrefix = "x86" in {
>        : GCCBuiltin<"__builtin_ia32_mwaitx">,
>          Intrinsic<[], [ llvm_i32_ty, llvm_i32_ty, llvm_i32_ty ], []>;
>  }
> +
>
> +//===----------------------------------------------------------------------===//
> +// Bit Scan intrinsics
> +let TargetPrefix = "x86" in {
> +  def int_x86_bit_scan_forward_32 :
> GCCBuiltin<"__builtin_ia32_bit_scan_forward">,
> +      Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem]>;
> +
> +  def int_x86_bit_scan_reverse_32 :
> GCCBuiltin<"__builtin_ia32_bit_scan_reverse">,
> +      Intrinsic<[llvm_i32_ty], [llvm_i32_ty], [IntrNoMem]>;

+}
>
> Modified: llvm/trunk/lib/Target/X86/X86IntrinsicsInfo.h
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86IntrinsicsInfo.h?rev=271386&r1=271385&r2=271386&view=diff
>
> ==============================================================================
> --- llvm/trunk/lib/Target/X86/X86IntrinsicsInfo.h (original)
> +++ llvm/trunk/lib/Target/X86/X86IntrinsicsInfo.h Wed Jun  1 07:02:37 2016
> @@ -2133,6 +2133,8 @@ static const IntrinsicData  IntrinsicsWi
>                       X86ISD::SCALAR_FP_TO_UINT_RND, 0),
>    X86_INTRINSIC_DATA(avx512_vcvtss2usi64, INTR_TYPE_2OP,
>                       X86ISD::SCALAR_FP_TO_UINT_RND, 0),
> +  X86_INTRINSIC_DATA(bit_scan_forward_32,  INTR_TYPE_1OP, X86ISD::BSF, 0),
> +  X86_INTRINSIC_DATA(bit_scan_reverse_32,  INTR_TYPE_1OP, X86ISD::BSR, 0),
>    X86_INTRINSIC_DATA(fma_vfmadd_pd,        INTR_TYPE_3OP, X86ISD::FMADD,
> 0),
>    X86_INTRINSIC_DATA(fma_vfmadd_pd_256,    INTR_TYPE_3OP, X86ISD::FMADD,
> 0),
>    X86_INTRINSIC_DATA(fma_vfmadd_ps,        INTR_TYPE_3OP, X86ISD::FMADD,
> 0),
>
> Added: llvm/trunk/test/CodeGen/X86/bitscan.ll
> URL:
> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/bitscan.ll?rev=271386&view=auto
>
> ==============================================================================
> --- llvm/trunk/test/CodeGen/X86/bitscan.ll (added)
> +++ llvm/trunk/test/CodeGen/X86/bitscan.ll Wed Jun  1 07:02:37 2016
> @@ -0,0 +1,23 @@
> +; RUN: llc < %s -mtriple=x86_64-unknown-unknown -mcpu=corei7 | FileCheck
> %s --check-prefix=ALL --check-prefix=64-BIT
> +; RUN: llc < %s -mtriple=i386-unknown-unknown -mcpu=corei7 | FileCheck %s
> --check-prefix=ALL --check-prefix=32-BIT
> +declare i32 @llvm.x86.bit.scan.forward.32(i32 %val)
> +declare i32 @llvm.x86.bit.scan.reverse.32(i32 %val)
> +
> +define i32 @test_bsf(i32 %val) {
> +  %call = call i32 @llvm.x86.bit.scan.forward.32(i32 %val)
> +  ret i32 %call
> +
> +; ALL-LABEL: test_bsf:
> +; 64-BIT:    bsfl %edi, %eax
> +; 32-BIT:    bsfl 4(%esp), %eax
> +}
> +
> +define i32 @test_bsr(i32 %val) {
> +  %call = call i32 @llvm.x86.bit.scan.reverse.32(i32 %val)
> +  ret i32 %call
> +
> +; ALL-LABEL: test_bsr:
> +; 64-BIT:    bsrl %edi, %eax
> +; 32-BIT:    bsrl 4(%esp), %eax
> +}
> +
>
>
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