[SelectionDAG] Support 'bit preserving' floating points bitcasts on computeKnownBits/ComputeNumSignBits

For cases where we know the floating point representations match the bitcasted integer equivalent, allow bitcasting to these types.

This is especially useful for the X86 floating point compare results which return all/zero bits but as a floating point type.

Differential Revision: https://reviews.llvm.org/D39289

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316831 91177308-0d34-0410-b5e6-96231b3b80d8

Author: RKSimon

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -2096,6 +2096,12 @@ void SelectionDAG::computeKnownBits(SDValue Op, KnownBits &Known,
     Known.Zero = ~Known.One;
     return;
   }
+  if (auto *C = dyn_cast<ConstantFPSDNode>(Op)) {
+    // We know all of the bits for a constant fp!
+    Known.One = C->getValueAPF().bitcastToAPInt();
+    Known.Zero = ~Known.One;
+    return;
+  }
 
   if (Depth == 6)
     return;  // Limit search depth.
@@ -2219,10 +2225,11 @@ void SelectionDAG::computeKnownBits(SDValue Op, KnownBits &Known,
   }
   case ISD::BITCAST: {
     SDValue N0 = Op.getOperand(0);
-    unsigned SubBitWidth = N0.getScalarValueSizeInBits();
+    EVT SubVT = N0.getValueType();
+    unsigned SubBitWidth = SubVT.getScalarSizeInBits();
 
-    // Ignore bitcasts from floating point.
-    if (!N0.getValueType().isInteger())
+    // Ignore bitcasts from unsupported types.
+    if (!(SubVT.isInteger() || SubVT.isFloatingPoint()))
       break;
 
     // Fast handling of 'identity' bitcasts.
@@ -2960,7 +2967,7 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, unsigned Depth) const {
 unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
                                           unsigned Depth) const {
   EVT VT = Op.getValueType();
-  assert(VT.isInteger() && "Invalid VT!");
+  assert((VT.isInteger() || VT.isFloatingPoint()) && "Invalid VT!");
   unsigned VTBits = VT.getScalarSizeInBits();
   unsigned NumElts = DemandedElts.getBitWidth();
   unsigned Tmp, Tmp2;
@@ -3041,10 +3048,11 @@ unsigned SelectionDAG::ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
 
   case ISD::BITCAST: {
     SDValue N0 = Op.getOperand(0);
-    unsigned SrcBits = N0.getScalarValueSizeInBits();
+    EVT SrcVT = N0.getValueType();
+    unsigned SrcBits = SrcVT.getScalarSizeInBits();
 
-    // Ignore bitcasts from floating point.
-    if (!N0.getValueType().isInteger())
+    // Ignore bitcasts from unsupported types..
+    if (!(SrcVT.isInteger() || SrcVT.isFloatingPoint()))
       break;
 
     // Fast handling of 'identity' bitcasts.

test/CodeGen/X86/avx512-vec-cmp.ll

@@ -1245,7 +1245,7 @@ define <2 x i64> @test46(<2 x float> %x, <2 x float> %y) #0 {
 ; KNL:       ## BB#0:
 ; KNL-NEXT:    vcmpeqps %xmm1, %xmm0, %xmm0
 ; KNL-NEXT:    vpmovsxdq %xmm0, %xmm0
-; KNL-NEXT:    vpand {{.*}}(%rip), %xmm0, %xmm0
+; KNL-NEXT:    vpsrlq $63, %xmm0, %xmm0
 ; KNL-NEXT:    retq
 ;
 ; SKX-LABEL: test46:

test/CodeGen/X86/bitcast-and-setcc-256.ll

@@ -274,50 +274,19 @@ define i8 @v8i32(<8 x i32> %a, <8 x i32> %b, <8 x i32> %c, <8 x i32> %d) {
 }
 
 define i8 @v8f32(<8 x float> %a, <8 x float> %b, <8 x float> %c, <8 x float> %d) {
-; SSE2-LABEL: v8f32:
-; SSE2:       # BB#0:
-; SSE2-NEXT:    cmpltps %xmm1, %xmm3
-; SSE2-NEXT:    pshuflw {{.*#+}} xmm1 = xmm3[0,2,2,3,4,5,6,7]
-; SSE2-NEXT:    pshufhw {{.*#+}} xmm1 = xmm1[0,1,2,3,4,6,6,7]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[0,2,2,3]
-; SSE2-NEXT:    cmpltps %xmm0, %xmm2
-; SSE2-NEXT:    pshuflw {{.*#+}} xmm0 = xmm2[0,2,2,3,4,5,6,7]
-; SSE2-NEXT:    pshufhw {{.*#+}} xmm0 = xmm0[0,1,2,3,4,6,6,7]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm0 = xmm0[0,2,2,3]
-; SSE2-NEXT:    punpcklqdq {{.*#+}} xmm0 = xmm0[0],xmm1[0]
-; SSE2-NEXT:    cmpltps %xmm5, %xmm7
-; SSE2-NEXT:    pshuflw {{.*#+}} xmm1 = xmm7[0,2,2,3,4,5,6,7]
-; SSE2-NEXT:    pshufhw {{.*#+}} xmm1 = xmm1[0,1,2,3,4,6,6,7]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm1 = xmm1[0,2,2,3]
-; SSE2-NEXT:    cmpltps %xmm4, %xmm6
-; SSE2-NEXT:    pshuflw {{.*#+}} xmm2 = xmm6[0,2,2,3,4,5,6,7]
-; SSE2-NEXT:    pshufhw {{.*#+}} xmm2 = xmm2[0,1,2,3,4,6,6,7]
-; SSE2-NEXT:    pshufd {{.*#+}} xmm2 = xmm2[0,2,2,3]
-; SSE2-NEXT:    punpcklqdq {{.*#+}} xmm2 = xmm2[0],xmm1[0]
-; SSE2-NEXT:    pand %xmm0, %xmm2
-; SSE2-NEXT:    packsswb %xmm0, %xmm2
-; SSE2-NEXT:    pmovmskb %xmm2, %eax
-; SSE2-NEXT:    # kill: %AL<def> %AL<kill> %EAX<kill>
-; SSE2-NEXT:    ret{{[l|q]}}
-;
-; SSSE3-LABEL: v8f32:
-; SSSE3:       # BB#0:
-; SSSE3-NEXT:    cmpltps %xmm1, %xmm3
-; SSSE3-NEXT:    movdqa {{.*#+}} xmm1 = [0,1,4,5,8,9,12,13,8,9,12,13,12,13,14,15]
-; SSSE3-NEXT:    pshufb %xmm1, %xmm3
-; SSSE3-NEXT:    cmpltps %xmm0, %xmm2
-; SSSE3-NEXT:    pshufb %xmm1, %xmm2
-; SSSE3-NEXT:    punpcklqdq {{.*#+}} xmm2 = xmm2[0],xmm3[0]
-; SSSE3-NEXT:    cmpltps %xmm5, %xmm7
-; SSSE3-NEXT:    pshufb %xmm1, %xmm7
-; SSSE3-NEXT:    cmpltps %xmm4, %xmm6
-; SSSE3-NEXT:    pshufb %xmm1, %xmm6
-; SSSE3-NEXT:    punpcklqdq {{.*#+}} xmm6 = xmm6[0],xmm7[0]
-; SSSE3-NEXT:    pand %xmm2, %xmm6
-; SSSE3-NEXT:    packsswb %xmm0, %xmm6
-; SSSE3-NEXT:    pmovmskb %xmm6, %eax
-; SSSE3-NEXT:    # kill: %AL<def> %AL<kill> %EAX<kill>
-; SSSE3-NEXT:    ret{{[l|q]}}
+; SSE2-SSSE3-LABEL: v8f32:
+; SSE2-SSSE3:       # BB#0:
+; SSE2-SSSE3-NEXT:    cmpltps %xmm1, %xmm3
+; SSE2-SSSE3-NEXT:    cmpltps %xmm0, %xmm2
+; SSE2-SSSE3-NEXT:    packssdw %xmm3, %xmm2
+; SSE2-SSSE3-NEXT:    cmpltps %xmm5, %xmm7
+; SSE2-SSSE3-NEXT:    cmpltps %xmm4, %xmm6
+; SSE2-SSSE3-NEXT:    packssdw %xmm7, %xmm6
+; SSE2-SSSE3-NEXT:    pand %xmm2, %xmm6
+; SSE2-SSSE3-NEXT:    packsswb %xmm0, %xmm6
+; SSE2-SSSE3-NEXT:    pmovmskb %xmm6, %eax
+; SSE2-SSSE3-NEXT:    # kill: %AL<def> %AL<kill> %EAX<kill>
+; SSE2-SSSE3-NEXT:    ret{{[l|q]}}
 ;
 ; AVX12-LABEL: v8f32:
 ; AVX12:       # BB#0:

test/CodeGen/X86/bitcast-and-setcc-512.ll

@@ -135,40 +135,39 @@ define i8 @v8i64(<8 x i64> %a, <8 x i64> %b, <8 x i64> %c, <8 x i64> %d) {
 define i8 @v8f64(<8 x double> %a, <8 x double> %b, <8 x double> %c, <8 x double> %d) {
 ; SSE-LABEL: v8f64:
 ; SSE:       # BB#0:
+; SSE-NEXT:    movapd {{[0-9]+}}(%rsp), %xmm8
 ; SSE-NEXT:    movapd {{[0-9]+}}(%rsp), %xmm9
 ; SSE-NEXT:    movapd {{[0-9]+}}(%rsp), %xmm10
-; SSE-NEXT:    movapd {{[0-9]+}}(%rsp), %xmm8
 ; SSE-NEXT:    movapd {{[0-9]+}}(%rsp), %xmm11
-; SSE-NEXT:    cmpltpd %xmm3, %xmm7
-; SSE-NEXT:    cmpltpd %xmm2, %xmm6
-; SSE-NEXT:    shufps {{.*#+}} xmm6 = xmm6[0,2],xmm7[0,2]
-; SSE-NEXT:    movdqa {{.*#+}} xmm2 = [0,1,4,5,4,5,6,7,0,1,4,5,8,9,12,13]
-; SSE-NEXT:    pshufb %xmm2, %xmm6
 ; SSE-NEXT:    cmpltpd %xmm1, %xmm5
 ; SSE-NEXT:    shufps {{.*#+}} xmm5 = xmm5[0,2,2,3]
 ; SSE-NEXT:    pshuflw {{.*#+}} xmm1 = xmm5[0,2,2,3,4,5,6,7]
 ; SSE-NEXT:    cmpltpd %xmm0, %xmm4
 ; SSE-NEXT:    shufps {{.*#+}} xmm4 = xmm4[0,2,2,3]
 ; SSE-NEXT:    pshuflw {{.*#+}} xmm0 = xmm4[0,2,2,3,4,5,6,7]
 ; SSE-NEXT:    punpckldq {{.*#+}} xmm0 = xmm0[0],xmm1[0],xmm0[1],xmm1[1]
-; SSE-NEXT:    pblendw {{.*#+}} xmm0 = xmm0[0,1,2,3],xmm6[4,5,6,7]
+; SSE-NEXT:    cmpltpd %xmm3, %xmm7
+; SSE-NEXT:    cmpltpd %xmm2, %xmm6
+; SSE-NEXT:    shufps {{.*#+}} xmm6 = xmm6[0,2],xmm7[0,2]
+; SSE-NEXT:    packssdw %xmm6, %xmm6
+; SSE-NEXT:    pblendw {{.*#+}} xmm6 = xmm0[0,1,2,3],xmm6[4,5,6,7]
 ; SSE-NEXT:    cmpltpd {{[0-9]+}}(%rsp), %xmm11
-; SSE-NEXT:    cmpltpd {{[0-9]+}}(%rsp), %xmm8
-; SSE-NEXT:    shufps {{.*#+}} xmm8 = xmm8[0,2],xmm11[0,2]
-; SSE-NEXT:    pshufb %xmm2, %xmm8
+; SSE-NEXT:    shufps {{.*#+}} xmm11 = xmm11[0,2,2,3]
+; SSE-NEXT:    pshuflw {{.*#+}} xmm0 = xmm11[0,2,2,3,4,5,6,7]
 ; SSE-NEXT:    cmpltpd {{[0-9]+}}(%rsp), %xmm10
 ; SSE-NEXT:    shufps {{.*#+}} xmm10 = xmm10[0,2,2,3]
 ; SSE-NEXT:    pshuflw {{.*#+}} xmm1 = xmm10[0,2,2,3,4,5,6,7]
+; SSE-NEXT:    punpckldq {{.*#+}} xmm1 = xmm1[0],xmm0[0],xmm1[1],xmm0[1]
 ; SSE-NEXT:    cmpltpd {{[0-9]+}}(%rsp), %xmm9
-; SSE-NEXT:    shufps {{.*#+}} xmm9 = xmm9[0,2,2,3]
-; SSE-NEXT:    pshuflw {{.*#+}} xmm2 = xmm9[0,2,2,3,4,5,6,7]
-; SSE-NEXT:    punpckldq {{.*#+}} xmm2 = xmm2[0],xmm1[0],xmm2[1],xmm1[1]
-; SSE-NEXT:    pblendw {{.*#+}} xmm2 = xmm2[0,1,2,3],xmm8[4,5,6,7]
-; SSE-NEXT:    pand %xmm0, %xmm2
-; SSE-NEXT:    psllw $15, %xmm2
-; SSE-NEXT:    psraw $15, %xmm2
-; SSE-NEXT:    packsswb %xmm0, %xmm2
-; SSE-NEXT:    pmovmskb %xmm2, %eax
+; SSE-NEXT:    cmpltpd {{[0-9]+}}(%rsp), %xmm8
+; SSE-NEXT:    shufps {{.*#+}} xmm8 = xmm8[0,2],xmm9[0,2]
+; SSE-NEXT:    packssdw %xmm8, %xmm8
+; SSE-NEXT:    pblendw {{.*#+}} xmm8 = xmm1[0,1,2,3],xmm8[4,5,6,7]
+; SSE-NEXT:    pand %xmm6, %xmm8
+; SSE-NEXT:    psllw $15, %xmm8
+; SSE-NEXT:    psraw $15, %xmm8
+; SSE-NEXT:    packsswb %xmm0, %xmm8
+; SSE-NEXT:    pmovmskb %xmm8, %eax
 ; SSE-NEXT:    # kill: %AL<def> %AL<kill> %EAX<kill>
 ; SSE-NEXT:    ret{{[l|q]}}
 ;
@@ -718,37 +717,23 @@ define i16 @v16f32(<16 x float> %a, <16 x float> %b, <16 x float> %c, <16 x floa
 ; SSE-LABEL: v16f32:
 ; SSE:       # BB#0:
 ; SSE-NEXT:    movaps {{[0-9]+}}(%rsp), %xmm8
-; SSE-NEXT:    movaps {{[0-9]+}}(%rsp), %xmm10
 ; SSE-NEXT:    movaps {{[0-9]+}}(%rsp), %xmm9
+; SSE-NEXT:    movaps {{[0-9]+}}(%rsp), %xmm10
 ; SSE-NEXT:    movaps {{[0-9]+}}(%rsp), %xmm11
 ; SSE-NEXT:    cmpltps %xmm3, %xmm7
-; SSE-NEXT:    movdqa {{.*#+}} xmm3 = [0,1,4,5,8,9,12,13,8,9,12,13,12,13,14,15]
-; SSE-NEXT:    pshufb %xmm3, %xmm7
 ; SSE-NEXT:    cmpltps %xmm2, %xmm6
-; SSE-NEXT:    pshufb %xmm3, %xmm6
-; SSE-NEXT:    punpcklqdq {{.*#+}} xmm6 = xmm6[0],xmm7[0]
-; SSE-NEXT:    movdqa {{.*#+}} xmm2 = <0,2,4,6,8,10,12,14,u,u,u,u,u,u,u,u>
-; SSE-NEXT:    pshufb %xmm2, %xmm6
+; SSE-NEXT:    packssdw %xmm7, %xmm6
 ; SSE-NEXT:    cmpltps %xmm1, %xmm5
-; SSE-NEXT:    pshufb %xmm3, %xmm5
 ; SSE-NEXT:    cmpltps %xmm0, %xmm4
-; SSE-NEXT:    pshufb %xmm3, %xmm4
-; SSE-NEXT:    punpcklqdq {{.*#+}} xmm4 = xmm4[0],xmm5[0]
-; SSE-NEXT:    pshufb %xmm2, %xmm4
-; SSE-NEXT:    punpcklqdq {{.*#+}} xmm4 = xmm4[0],xmm6[0]
+; SSE-NEXT:    packssdw %xmm5, %xmm4
+; SSE-NEXT:    packsswb %xmm6, %xmm4
 ; SSE-NEXT:    cmpltps {{[0-9]+}}(%rsp), %xmm11
-; SSE-NEXT:    pshufb %xmm3, %xmm11
-; SSE-NEXT:    cmpltps {{[0-9]+}}(%rsp), %xmm9
-; SSE-NEXT:    pshufb %xmm3, %xmm9
-; SSE-NEXT:    punpcklqdq {{.*#+}} xmm9 = xmm9[0],xmm11[0]
-; SSE-NEXT:    pshufb %xmm2, %xmm9
 ; SSE-NEXT:    cmpltps {{[0-9]+}}(%rsp), %xmm10
-; SSE-NEXT:    pshufb %xmm3, %xmm10
+; SSE-NEXT:    packssdw %xmm11, %xmm10
+; SSE-NEXT:    cmpltps {{[0-9]+}}(%rsp), %xmm9
 ; SSE-NEXT:    cmpltps {{[0-9]+}}(%rsp), %xmm8
-; SSE-NEXT:    pshufb %xmm3, %xmm8
-; SSE-NEXT:    punpcklqdq {{.*#+}} xmm8 = xmm8[0],xmm10[0]
-; SSE-NEXT:    pshufb %xmm2, %xmm8
-; SSE-NEXT:    punpcklqdq {{.*#+}} xmm8 = xmm8[0],xmm9[0]
+; SSE-NEXT:    packssdw %xmm9, %xmm8
+; SSE-NEXT:    packsswb %xmm10, %xmm8
 ; SSE-NEXT:    pand %xmm4, %xmm8
 ; SSE-NEXT:    pmovmskb %xmm8, %eax
 ; SSE-NEXT:    # kill: %AX<def> %AX<kill> %EAX<kill>
@@ -759,22 +744,17 @@ define i16 @v16f32(<16 x float> %a, <16 x float> %b, <16 x float> %c, <16 x floa
 ; AVX12-NEXT:    vcmpltps %ymm1, %ymm3, %ymm1
 ; AVX12-NEXT:    vextractf128 $1, %ymm1, %xmm3
 ; AVX12-NEXT:    vpackssdw %xmm3, %xmm1, %xmm1
-; AVX12-NEXT:    vmovdqa {{.*#+}} xmm3 = <0,2,4,6,8,10,12,14,u,u,u,u,u,u,u,u>
-; AVX12-NEXT:    vpshufb %xmm3, %xmm1, %xmm1
 ; AVX12-NEXT:    vcmpltps %ymm0, %ymm2, %ymm0
 ; AVX12-NEXT:    vextractf128 $1, %ymm0, %xmm2
 ; AVX12-NEXT:    vpackssdw %xmm2, %xmm0, %xmm0
-; AVX12-NEXT:    vpshufb %xmm3, %xmm0, %xmm0
-; AVX12-NEXT:    vpunpcklqdq {{.*#+}} xmm0 = xmm0[0],xmm1[0]
+; AVX12-NEXT:    vpacksswb %xmm1, %xmm0, %xmm0
 ; AVX12-NEXT:    vcmpltps %ymm5, %ymm7, %ymm1
 ; AVX12-NEXT:    vextractf128 $1, %ymm1, %xmm2
 ; AVX12-NEXT:    vpackssdw %xmm2, %xmm1, %xmm1
-; AVX12-NEXT:    vpshufb %xmm3, %xmm1, %xmm1
 ; AVX12-NEXT:    vcmpltps %ymm4, %ymm6, %ymm2
-; AVX12-NEXT:    vextractf128 $1, %ymm2, %xmm4
-; AVX12-NEXT:    vpackssdw %xmm4, %xmm2, %xmm2
-; AVX12-NEXT:    vpshufb %xmm3, %xmm2, %xmm2
-; AVX12-NEXT:    vpunpcklqdq {{.*#+}} xmm1 = xmm2[0],xmm1[0]
+; AVX12-NEXT:    vextractf128 $1, %ymm2, %xmm3
+; AVX12-NEXT:    vpackssdw %xmm3, %xmm2, %xmm2
+; AVX12-NEXT:    vpacksswb %xmm1, %xmm2, %xmm1
 ; AVX12-NEXT:    vpand %xmm1, %xmm0, %xmm0
 ; AVX12-NEXT:    vpmovmskb %xmm0, %eax
 ; AVX12-NEXT:    # kill: %AX<def> %AX<kill> %EAX<kill>