[X86][SSE1] Add MOVLHPS/MOVHLPS lowering and memory folding support

[RKSimon]

Summary

As discussed on PR26491, this patch adds support for lowering v4f32 shuffles to the MOVLHPS/MOVHLPS instructions. It also adds support for memory folding with their MOVLPS/MOVHPS load equivalents.

This first patch only really helps SSE1 targets as SSE2+ targets will widen the shuffle mask and use v2f64 equivalents (although they still combine to MOVLHPS/MOVHLPS for v2f64 splats). This will have to be addressed in a future patch, most likely when we add support for binary target shuffle combines.

[spatel]

Shouldn't MOVHPS/MOVLPS/MOVLHPS/MOVHLPS be in "hasPartialRegUpdate()"? I wonder if the partial reg update is why we weren't trying to lower these before.

If that's correct, I think a FIXME comment is fine for now.

lib/Target/X86/X86InstrInfo.cpp

29–37

Extra indent here.

30

Does the AVX case doesn't need the alignment restriction? I don't think we'd actually generate this instruction in the first place if we have AVX, so it might be a moot point. But maybe worthy of a code comment.

[RKSimon]

Updated based on Sanjay's comments.

[spatel]

lib/Target/X86/X86InstrInfo.cpp

5745

Should MOVHPS/MOVLPS/MOVLHPS/MOVHLPS be in this list?

[RKSimon]

Thanks Sanjay - I missed that comment! The AMD 15h SOG highlights the MOVHP*/MOVLP* loads as having a merge dependency, I've added them to hasPartialRegUpdate().

[spatel]

Please see another inline comment for hasPartialRegUpdate(). LGTM after that is addressed.

lib/Target/X86/X86InstrInfo.cpp

5763–5766

We're creating MOVLHPSrr / MOVHLPSrr with this patch, so I think those should be included too.

lib/Target/X86/X86ISelLowering.cpp

if (SDValue V = lowerVectorShuffleAsInsertPS(Op, V1, V2, Mask, DAG))
       return V;
 
     if (!isSingleSHUFPSMask(Mask))
       if (SDValue BlendPerm = lowerVectorShuffleAsBlendAndPermute(
               DL, MVT::v4f32, V1, V2, Mask, DAG))
         return BlendPerm;
   }
 
+  // Use low/high mov instructions.
+  if (isShuffleEquivalent(V1, V2, Mask, {0, 1, 4, 5}))
+    return DAG.getNode(X86ISD::MOVLHPS, DL, MVT::v4f32, V1, V2);
+  if (isShuffleEquivalent(V1, V2, Mask, {2, 3, 6, 7}))
+    return DAG.getNode(X86ISD::MOVHLPS, DL, MVT::v4f32, V2, V1);
+
   // Use dedicated unpack instructions for masks that match their pattern.
   if (SDValue V =
           lowerVectorShuffleWithUNPCK(DL, MVT::v4f32, Mask, V1, V2, DAG))
     return V;
 
   // Otherwise fall back to a SHUFPS lowering strategy.
   return lowerVectorShuffleWithSHUFPS(DL, MVT::v4f32, Mask, V1, V2, DAG);
 }

lib/Target/X86/X86InstrInfo.cpp

 #include "llvm/CodeGen/LiveVariables.h"
 #include "llvm/CodeGen/MachineConstantPool.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/CodeGen/StackMaps.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetOptions.h"
 #include <limits>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "x86-instr-info"
 
 #define GET_INSTRINFO_CTOR_DTOR
static const X86MemoryFoldTableEntry MemoryFoldTable2[] = {
     { X86::MAXSSrr,         X86::MAXSSrm,       0 },
     { X86::MAXSSrr_Int,     X86::MAXSSrm_Int,   0 },
     { X86::MINPDrr,         X86::MINPDrm,       TB_ALIGN_16 },
     { X86::MINPSrr,         X86::MINPSrm,       TB_ALIGN_16 },
     { X86::MINSDrr,         X86::MINSDrm,       0 },
     { X86::MINSDrr_Int,     X86::MINSDrm_Int,   0 },
     { X86::MINSSrr,         X86::MINSSrm,       0 },
     { X86::MINSSrr_Int,     X86::MINSSrm_Int,   0 },
+    { X86::MOVLHPSrr,       X86::MOVHPSrm,      TB_NO_REVERSE },
     { X86::MPSADBWrri,      X86::MPSADBWrmi,    TB_ALIGN_16 },
     { X86::MULPDrr,         X86::MULPDrm,       TB_ALIGN_16 },
     { X86::MULPSrr,         X86::MULPSrm,       TB_ALIGN_16 },
     { X86::MULSDrr,         X86::MULSDrm,       0 },
     { X86::MULSDrr_Int,     X86::MULSDrm_Int,   0 },
     { X86::MULSSrr,         X86::MULSSrm,       0 },
     { X86::MULSSrr_Int,     X86::MULSSrm_Int,   0 },
     { X86::OR16rr,          X86::OR16rm,        0 },
static const X86MemoryFoldTableEntry MemoryFoldTable2[] = {
     { X86::VMAXSSrr,          X86::VMAXSSrm,           0 },
     { X86::VMAXSSrr_Int,      X86::VMAXSSrm_Int,       0 },
     { X86::VMINPDrr,          X86::VMINPDrm,           0 },
     { X86::VMINPSrr,          X86::VMINPSrm,           0 },
     { X86::VMINSDrr,          X86::VMINSDrm,           0 },
     { X86::VMINSDrr_Int,      X86::VMINSDrm_Int,       0 },
     { X86::VMINSSrr,          X86::VMINSSrm,           0 },
     { X86::VMINSSrr_Int,      X86::VMINSSrm_Int,       0 },
+    { X86::VMOVLHPSrr,        X86::VMOVHPSrm,          TB_NO_REVERSE },
     { X86::VMPSADBWrri,       X86::VMPSADBWrmi,        0 },
     { X86::VMULPDrr,          X86::VMULPDrm,           0 },
     { X86::VMULPSrr,          X86::VMULPSrm,           0 },
     { X86::VMULSDrr,          X86::VMULSDrm,           0 },
     { X86::VMULSDrr_Int,      X86::VMULSDrm_Int,       0 },
     { X86::VMULSSrr,          X86::VMULSSrm,           0 },
     { X86::VMULSSrr_Int,      X86::VMULSSrm_Int,       0 },
     { X86::VORPDrr,           X86::VORPDrm,            0 },
if (OpNum == 2) {
                                                  : X86::INSERTPSrm);
         MachineInstr *NewMI =
             FuseInst(MF, NewOpCode, OpNum, MOs, InsertPt, MI, *this, PtrOffset);
         NewMI->getOperand(NewMI->getNumOperands() - 1).setImm(NewImm);
         return NewMI;
       }
     }
     break;
+  case X86::MOVHLPSrr:
+  case X86::VMOVHLPSrr:
+    // Move the upper 64-bits of the second operand to the lower 64-bits.
+    // To fold the load, adjust the pointer to the upper and use (V)MOVLPS.
+    // TODO: In most cases AVX doesn't have a 8-byte alignment requirement.
+    if (OpNum == 2) {
+      unsigned RCSize = getRegClass(MI->getDesc(), OpNum, &RI, MF)->getSize();
+      if (Size <= RCSize && 8 <= Align) {
+        unsigned NewOpCode =
+            (MI->getOpcode() == X86::VMOVHLPSrr ? X86::VMOVLPSrm
+                                                : X86::MOVLPSrm);
+        MachineInstr *NewMI =
+            FuseInst(MF, NewOpCode, OpNum, MOs, InsertPt, MI, *this, 8);
+        return NewMI;
+      }
+    }
+    break;
   };
 
   return nullptr;
 }
 
 MachineInstr *X86InstrInfo::foldMemoryOperandImpl(
     MachineFunction &MF, MachineInstr *MI, unsigned OpNum,
     ArrayRef<MachineOperand> MOs, MachineBasicBlock::iterator InsertPt,

 ///   movss (%rdi), %xmm0
 ///   cvtss2sd %xmm0, %xmm0
 ///
 /// Instead of
 ///   cvtss2sd (%rdi), %xmm0
 ///
 /// FIXME: This should be turned into a TSFlags.
 ///
 static bool hasPartialRegUpdate(unsigned Opcode) {
   switch (Opcode) {
   case X86::CVTSI2SSrr:
   case X86::CVTSI2SSrm:
   case X86::CVTSI2SS64rr:
   case X86::CVTSI2SS64rm:
   case X86::CVTSI2SDrr:
   case X86::CVTSI2SDrm:
   case X86::CVTSI2SD64rr:
   case X86::CVTSI2SD64rm:
   case X86::CVTSD2SSrr:
   case X86::CVTSD2SSrm:
   case X86::Int_CVTSD2SSrr:
   case X86::Int_CVTSD2SSrm:
   case X86::CVTSS2SDrr:
   case X86::CVTSS2SDrm:
   case X86::Int_CVTSS2SDrr:
   case X86::Int_CVTSS2SDrm:
+  case X86::MOVHPDrm:
+  case X86::MOVHPSrm:
+  case X86::MOVLPDrm:
+  case X86::MOVLPSrm:
   case X86::RCPSSr:
   case X86::RCPSSm:
   case X86::RCPSSr_Int:
   case X86::RCPSSm_Int:
   case X86::ROUNDSDr:
   case X86::ROUNDSDm:
   case X86::ROUNDSDr_Int:
   case X86::ROUNDSSr:

test/CodeGen/X86/vector-shuffle-sse1.ll

 ; SSE1-NEXT:    shufps {{.*#+}} xmm0 = xmm0[1,1,3,3]
 ; SSE1-NEXT:    retq
   %shuffle = shufflevector <4 x float> %a, <4 x float> %b, <4 x i32> <i32 1, i32 1, i32 3, i32 3>
   ret <4 x float> %shuffle
 }
 define <4 x float> @shuffle_v4f32_0145(<4 x float> %a, <4 x float> %b) {
 ; SSE1-LABEL: shuffle_v4f32_0145:
 ; SSE1:       # BB#0:
-; SSE1-NEXT:    shufps {{.*#+}} xmm0 = xmm0[0,1],xmm1[0,1]
+; SSE1-NEXT:    movlhps {{.*#+}} xmm0 = xmm0[0],xmm1[0]
 ; SSE1-NEXT:    retq
   %shuffle = shufflevector <4 x float> %a, <4 x float> %b, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
   ret <4 x float> %shuffle
 }
 define <4 x float> @shuffle_v4f32_6723(<4 x float> %a, <4 x float> %b) {
 ; SSE1-LABEL: shuffle_v4f32_6723:
 ; SSE1:       # BB#0:
-; SSE1-NEXT:    shufps {{.*#+}} xmm1 = xmm1[2,3],xmm0[2,3]
-; SSE1-NEXT:    movaps %xmm1, %xmm0
+; SSE1-NEXT:    movhlps {{.*#+}} xmm0 = xmm1[1],xmm0[1]
 ; SSE1-NEXT:    retq
   %shuffle = shufflevector <4 x float> %a, <4 x float> %b, <4 x i32> <i32 6, i32 7, i32 2, i32 3>
   ret <4 x float> %shuffle
 }
 
 define <4 x float> @shuffle_v4f32_4zzz(<4 x float> %a) {
 ; SSE1-LABEL: shuffle_v4f32_4zzz:
 ; SSE1:       # BB#0:

 ; SSE1-NEXT:    movq (%rdi), %rax
 ; SSE1-NEXT:    movl %eax, -{{[0-9]+}}(%rsp)
 ; SSE1-NEXT:    shrq $32, %rax
 ; SSE1-NEXT:    movl %eax, -{{[0-9]+}}(%rsp)
 ; SSE1-NEXT:    movss {{.*#+}} xmm1 = mem[0],zero,zero,zero
 ; SSE1-NEXT:    movss {{.*#+}} xmm2 = mem[0],zero,zero,zero
 ; SSE1-NEXT:    unpcklps {{.*#+}} xmm1 = xmm1[0],xmm2[0],xmm1[1],xmm2[1]
 ; SSE1-NEXT:    xorps %xmm2, %xmm2
-; SSE1-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,1],xmm2[2,3]
+; SSE1-NEXT:    movlhps {{.*#+}} xmm1 = xmm1[0],xmm2[0]
 ; SSE1-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,1],xmm0[2,3]
 ; SSE1-NEXT:    movaps %xmm1, %xmm0
 ; SSE1-NEXT:    retq
   %a = load <2 x float>, <2 x float>* %ptr
   %v = shufflevector <2 x float> %a, <2 x float> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
   %shuffle = shufflevector <4 x float> %v, <4 x float> %b, <4 x i32> <i32 0, i32 1, i32 6, i32 7>
   ret <4 x float> %shuffle
 }
 
 define <4 x float> @insert_mem_hi_v4f32(<2 x float>* %ptr, <4 x float> %b) {
 ; SSE1-LABEL: insert_mem_hi_v4f32:
 ; SSE1:       # BB#0:
 ; SSE1-NEXT:    movq (%rdi), %rax
 ; SSE1-NEXT:    movl %eax, -{{[0-9]+}}(%rsp)
 ; SSE1-NEXT:    shrq $32, %rax
 ; SSE1-NEXT:    movl %eax, -{{[0-9]+}}(%rsp)
 ; SSE1-NEXT:    movss {{.*#+}} xmm1 = mem[0],zero,zero,zero
 ; SSE1-NEXT:    movss {{.*#+}} xmm2 = mem[0],zero,zero,zero
 ; SSE1-NEXT:    unpcklps {{.*#+}} xmm1 = xmm1[0],xmm2[0],xmm1[1],xmm2[1]
 ; SSE1-NEXT:    xorps %xmm2, %xmm2
-; SSE1-NEXT:    shufps {{.*#+}} xmm1 = xmm1[0,1],xmm2[2,3]
-; SSE1-NEXT:    shufps {{.*#+}} xmm0 = xmm0[0,1],xmm1[0,1]
+; SSE1-NEXT:    movlhps {{.*#+}} xmm1 = xmm1[0],xmm2[0]
+; SSE1-NEXT:    movlhps {{.*#+}} xmm0 = xmm0[0],xmm1[0]
 ; SSE1-NEXT:    retq
   %a = load <2 x float>, <2 x float>* %ptr
   %v = shufflevector <2 x float> %a, <2 x float> undef, <4 x i32> <i32 0, i32 1, i32 undef, i32 undef>
   %shuffle = shufflevector <4 x float> %v, <4 x float> %b, <4 x i32> <i32 4, i32 5, i32 0, i32 1>
   ret <4 x float> %shuffle
 }
 
 define <4 x float> @shuffle_mem_v4f32_3210(<4 x float>* %ptr) {
 ; SSE1-LABEL: shuffle_mem_v4f32_3210:
 ; SSE1:       # BB#0:
 ; SSE1-NEXT:    movaps (%rdi), %xmm0
 ; SSE1-NEXT:    shufps {{.*#+}} xmm0 = xmm0[3,2,1,0]
 ; SSE1-NEXT:    retq
   %a = load <4 x float>, <4 x float>* %ptr
   %shuffle = shufflevector <4 x float> %a, <4 x float> undef, <4 x i32> <i32 3, i32 2, i32 1, i32 0>
   ret <4 x float> %shuffle
 }
+define <4 x float> @shuffle_mem_v4f32_0145(<4 x float> %a, <4 x float>* %pb) {
+; SSE1-LABEL: shuffle_mem_v4f32_0145:
+; SSE1:       # BB#0:
+; SSE1-NEXT:    movhps (%rdi), %xmm0
+; SSE1-NEXT:    retq
+  %b = load <4 x float>, <4 x float>* %pb, align 16
+  %shuffle = shufflevector <4 x float> %a, <4 x float> %b, <4 x i32> <i32 0, i32 1, i32 4, i32 5>
+  ret <4 x float> %shuffle
+}
+define <4 x float> @shuffle_mem_v4f32_6723(<4 x float> %a, <4 x float>* %pb) {
+; SSE1-LABEL: shuffle_mem_v4f32_6723:
+; SSE1:       # BB#0:
+; SSE1-NEXT:    movlps 8(%rdi), %xmm0
+; SSE1-NEXT:    retq
+  %b = load <4 x float>, <4 x float>* %pb, align 16
+  %shuffle = shufflevector <4 x float> %a, <4 x float> %b, <4 x i32> <i32 6, i32 7, i32 2, i32 3>
+  ret <4 x float> %shuffle
+}