[PATCH] D28745: [InstCombine][SSE] Add DemandedElts support for PSHUFB instructions

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.
RKSimon added reviewers: m_zuckerman, craig.topper, spatel.
RKSimon added a subscriber: llvm-commits.
RKSimon set the repository for this revision to rL LLVM.

Simplify a pshufb shuffle mask based on the elements of the mask that are actually demanded.


Repository:
  rL LLVM

https://reviews.llvm.org/D28745

Files:
  lib/Transforms/InstCombine/InstCombineCalls.cpp
  lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
  test/Transforms/InstCombine/x86-pshufb.ll


Index: test/Transforms/InstCombine/x86-pshufb.ll
===================================================================
--- test/Transforms/InstCombine/x86-pshufb.ll
+++ test/Transforms/InstCombine/x86-pshufb.ll
@@ -469,15 +469,12 @@
 }
 
 ; Demanded elts tests.
-; FIXME: Missed opportunities to pass demanded elts through the pshufb shuffle mask
 
 define <16 x i8> @demanded_elts_insertion(<16 x i8> %InVec, <16 x i8> %BaseMask, i8 %M0, i8 %M15) {
 ; CHECK-LABEL: @demanded_elts_insertion(
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <16 x i8> %BaseMask, i8 %M0, i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <16 x i8> [[TMP1]], i8 %M15, i32 15
-; CHECK-NEXT:    [[TMP3:%.*]] = tail call <16 x i8> @llvm.x86.ssse3.pshuf.b.128(<16 x i8> %InVec, <16 x i8> [[TMP2]])
-; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <16 x i8> [[TMP3]], <16 x i8> undef, <16 x i32> <i32 undef, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 undef>
-; CHECK-NEXT:    ret <16 x i8> [[TMP4]]
+; CHECK-NEXT:    [[TMP1:%.*]] = tail call <16 x i8> @llvm.x86.ssse3.pshuf.b.128(<16 x i8> %InVec, <16 x i8> %BaseMask)
+; CHECK-NEXT:    [[TMP2:%.*]] = shufflevector <16 x i8> [[TMP1]], <16 x i8> undef, <16 x i32> <i32 undef, i32 14, i32 13, i32 12, i32 11, i32 10, i32 9, i32 8, i32 7, i32 6, i32 5, i32 4, i32 3, i32 2, i32 1, i32 undef>
+; CHECK-NEXT:    ret <16 x i8> [[TMP2]]
 ;
   %1 = insertelement <16 x i8> %BaseMask, i8 %M0, i32 0
   %2 = insertelement <16 x i8> %1, i8 %M15, i32 15
@@ -489,9 +486,8 @@
 define <32 x i8> @demanded_elts_insertion_avx2(<32 x i8> %InVec, <32 x i8> %BaseMask, i8 %M0, i8 %M22) {
 ; CHECK-LABEL: @demanded_elts_insertion_avx2(
 ; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <32 x i8> %BaseMask, i8 %M0, i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <32 x i8> [[TMP1]], i8 %M22, i32 22
-; CHECK-NEXT:    [[TMP3:%.*]] = tail call <32 x i8> @llvm.x86.avx2.pshuf.b(<32 x i8> %InVec, <32 x i8> [[TMP2]])
-; CHECK-NEXT:    ret <32 x i8> [[TMP3]]
+; CHECK-NEXT:    [[TMP2:%.*]] = tail call <32 x i8> @llvm.x86.avx2.pshuf.b(<32 x i8> %InVec, <32 x i8> [[TMP1]])
+; CHECK-NEXT:    ret <32 x i8> [[TMP2]]
 ;
   %1 = insertelement <32 x i8> %BaseMask, i8 %M0, i32 0
   %2 = insertelement <32 x i8> %1, i8 %M22, i32 22
@@ -502,11 +498,10 @@
 
 define <64 x i8> @demanded_elts_insertion_avx512(<64 x i8> %InVec, <64 x i8> %BaseMask, i8 %M0, i8 %M30) {
 ; CHECK-LABEL: @demanded_elts_insertion_avx512(
-; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <64 x i8> %BaseMask, i8 %M0, i32 0
-; CHECK-NEXT:    [[TMP2:%.*]] = insertelement <64 x i8> [[TMP1]], i8 %M30, i32 30
-; CHECK-NEXT:    [[TMP3:%.*]] = tail call <64 x i8> @llvm.x86.avx512.pshuf.b.512(<64 x i8> %InVec, <64 x i8> [[TMP2]])
-; CHECK-NEXT:    [[TMP4:%.*]] = shufflevector <64 x i8> [[TMP3]], <64 x i8> undef, <64 x i32> zeroinitializer
-; CHECK-NEXT:    ret <64 x i8> [[TMP4]]
+; CHECK-NEXT:    [[TMP1:%.*]] = insertelement <64 x i8> undef, i8 %M0, i32 0
+; CHECK-NEXT:    [[TMP2:%.*]] = tail call <64 x i8> @llvm.x86.avx512.pshuf.b.512(<64 x i8> %InVec, <64 x i8> [[TMP1]])
+; CHECK-NEXT:    [[TMP3:%.*]] = shufflevector <64 x i8> [[TMP2]], <64 x i8> undef, <64 x i32> zeroinitializer
+; CHECK-NEXT:    ret <64 x i8> [[TMP3]]
 ;
   %1 = insertelement <64 x i8> %BaseMask, i8 %M0, i32 0
   %2 = insertelement <64 x i8> %1, i8 %M30, i32 30
Index: lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
+++ lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
@@ -1472,6 +1472,16 @@
       break;
     }
 
+    case Intrinsic::x86_ssse3_pshuf_b_128:
+    case Intrinsic::x86_avx2_pshuf_b:
+    case Intrinsic::x86_avx512_pshuf_b_512: {
+      Value *Op1 = II->getArgOperand(1);
+      TmpV = SimplifyDemandedVectorElts(Op1, DemandedElts, UndefElts,
+                                        Depth + 1);
+      if (TmpV) { II->setArgOperand(1, TmpV); MadeChange = true; }
+      break;
+    }
+
     // SSE4A instructions leave the upper 64-bits of the 128-bit result
     // in an undefined state.
     case Intrinsic::x86_sse4a_extrq:
Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2315,10 +2315,20 @@
 
   case Intrinsic::x86_ssse3_pshuf_b_128:
   case Intrinsic::x86_avx2_pshuf_b:
-  case Intrinsic::x86_avx512_pshuf_b_512:
+  case Intrinsic::x86_avx512_pshuf_b_512: {
     if (Value *V = simplifyX86pshufb(*II, *Builder))
       return replaceInstUsesWith(*II, V);
+
+    unsigned VWidth = II->getType()->getVectorNumElements();
+    APInt UndefElts(VWidth, 0);
+    APInt DemandedElts = APInt::getAllOnesValue(VWidth);
+    if (Value *V = SimplifyDemandedVectorElts(II, DemandedElts, UndefElts)) {
+      if (V != II)
+        return replaceInstUsesWith(*II, V);
+      return II;
+    }
     break;
+  }
 
   case Intrinsic::x86_avx_vpermilvar_ps:
   case Intrinsic::x86_avx_vpermilvar_ps_256:


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