[SelectionDAG] Compute known bits and num sign bits for live out vector registers. Use it to add AssertZExt/AssertSExt in the live in basic blocks

[craig.topper]

Summary

We already support this for scalars, but it was explicitly disabled for vectors. In the updated test cases this allows us to see the upper bits are zero to use less multiply instructions to emulate a 64 bit multiply.

This should help with this ispc issue that a coworker pointed me to https://github.com/ispc/ispc/issues/1362

[spatel]

Does this patch do anything for PR11730?
https://bugs.llvm.org/show_bug.cgi?id=11730

If so, it would be good to add a test based on that.

lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

700 ↗

(On Diff #174679)

Code comment isn't correct now.

[craig.topper]

Update comment

[craig.topper]

This doesn't help PR11730 at all.

[spatel]

In D54725#1303758, @craig.topper wrote:

This doesn't help PR11730 at all.

Ok, thanks for checking. LGTM.

llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

for (unsigned i = 0; i != NumRegs; ++i) {
       }
 
       Chain = P.getValue(1);
       Parts[i] = P;
 
       // If the source register was virtual and if we know something about it,
       // add an assert node.
       if (!TargetRegisterInfo::isVirtualRegister(Regs[Part+i]) ||
-          !RegisterVT.isInteger() || RegisterVT.isVector())
+          !RegisterVT.isInteger())
         continue;
 
       const FunctionLoweringInfo::LiveOutInfo *LOI =
         FuncInfo.GetLiveOutRegInfo(Regs[Part+i]);
       if (!LOI)
         continue;
 
-      unsigned RegSize = RegisterVT.getSizeInBits();
+      unsigned RegSize = RegisterVT.getScalarSizeInBits();
       unsigned NumSignBits = LOI->NumSignBits;
       unsigned NumZeroBits = LOI->Known.countMinLeadingZeros();
 
       if (NumZeroBits == RegSize) {
         // The current value is a zero.
         // Explicitly express that as it would be easier for
         // optimizations to kick in.
         Parts[i] = DAG.getConstant(0, dl, RegisterVT);

llvm/trunk/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

do {
     // If this is a CopyToReg with a vreg dest, process it.
     if (N->getOpcode() != ISD::CopyToReg)
       continue;
 
     unsigned DestReg = cast<RegisterSDNode>(N->getOperand(1))->getReg();
     if (!TargetRegisterInfo::isVirtualRegister(DestReg))
       continue;
 
-    // Ignore non-scalar or non-integer values.
+    // Ignore non-integer values.
     SDValue Src = N->getOperand(2);
     EVT SrcVT = Src.getValueType();
-    if (!SrcVT.isInteger() || SrcVT.isVector())
+    if (!SrcVT.isInteger())
       continue;
 
     unsigned NumSignBits = CurDAG->ComputeNumSignBits(Src);
     CurDAG->computeKnownBits(Src, Known);
     FuncInfo->AddLiveOutRegInfo(DestReg, NumSignBits, Known);
   } while (!Worklist.empty());
 }
 

llvm/trunk/test/CodeGen/X86/vector-mul.ll

 ; FIXME: We should be able to insert an AssertZExt for this.
 define <2 x i64> @mul_v2i64_zext_cross_bb(<2 x i32>* %in, <2 x i32>* %y) {
 ; X86-LABEL: mul_v2i64_zext_cross_bb:
 ; X86:       # %bb.0:
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
 ; X86-NEXT:    pmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X86-NEXT:    pmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
-; X86-NEXT:    movdqa %xmm0, %xmm2
-; X86-NEXT:    pmuludq %xmm1, %xmm2
-; X86-NEXT:    psrlq $32, %xmm0
 ; X86-NEXT:    pmuludq %xmm1, %xmm0
-; X86-NEXT:    psllq $32, %xmm0
-; X86-NEXT:    paddq %xmm2, %xmm0
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: mul_v2i64_zext_cross_bb:
 ; X64:       # %bb.0:
 ; X64-NEXT:    pmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X64-NEXT:    pmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
-; X64-NEXT:    movdqa %xmm0, %xmm2
-; X64-NEXT:    pmuludq %xmm1, %xmm2
-; X64-NEXT:    psrlq $32, %xmm0
 ; X64-NEXT:    pmuludq %xmm1, %xmm0
-; X64-NEXT:    psllq $32, %xmm0
-; X64-NEXT:    paddq %xmm2, %xmm0
 ; X64-NEXT:    retq
 ;
 ; X64-AVX-LABEL: mul_v2i64_zext_cross_bb:
 ; X64-AVX:       # %bb.0:
 ; X64-AVX-NEXT:    vpmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X64-AVX-NEXT:    vpmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
-; X64-AVX-NEXT:    vpmuludq %xmm1, %xmm0, %xmm2
-; X64-AVX-NEXT:    vpsrlq $32, %xmm0, %xmm0
 ; X64-AVX-NEXT:    vpmuludq %xmm1, %xmm0, %xmm0
-; X64-AVX-NEXT:    vpsllq $32, %xmm0, %xmm0
-; X64-AVX-NEXT:    vpaddq %xmm0, %xmm2, %xmm0
 ; X64-AVX-NEXT:    retq
   %a = load <2 x i32>, <2 x i32>* %in
   %b = zext <2 x i32> %a to <2 x i64>
   br label %foo
 
 foo:
   %c = load <2 x i32>, <2 x i32>* %y
   %d = zext <2 x i32> %c to <2 x i64>
   %e = mul <2 x i64> %b, %d
   ret <2 x i64> %e
 }
 
 define <4 x i64> @mul_v4i64_zext_cross_bb(<4 x i32>* %in, <4 x i32>* %y) {
 ; X86-LABEL: mul_v4i64_zext_cross_bb:
 ; X86:       # %bb.0:
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %ecx
 ; X86-NEXT:    pmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
 ; X86-NEXT:    pmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X86-NEXT:    pmovzxdq {{.*#+}} xmm2 = mem[0],zero,mem[1],zero
-; X86-NEXT:    pmovzxdq {{.*#+}} xmm3 = mem[0],zero,mem[1],zero
-; X86-NEXT:    movdqa %xmm0, %xmm4
-; X86-NEXT:    pmuludq %xmm3, %xmm4
-; X86-NEXT:    psrlq $32, %xmm0
-; X86-NEXT:    pmuludq %xmm3, %xmm0
-; X86-NEXT:    psllq $32, %xmm0
-; X86-NEXT:    paddq %xmm4, %xmm0
-; X86-NEXT:    movdqa %xmm1, %xmm3
-; X86-NEXT:    pmuludq %xmm2, %xmm3
-; X86-NEXT:    psrlq $32, %xmm1
 ; X86-NEXT:    pmuludq %xmm2, %xmm1
-; X86-NEXT:    psllq $32, %xmm1
-; X86-NEXT:    paddq %xmm3, %xmm1
+; X86-NEXT:    pmovzxdq {{.*#+}} xmm2 = mem[0],zero,mem[1],zero
+; X86-NEXT:    pmuludq %xmm2, %xmm0
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: mul_v4i64_zext_cross_bb:
 ; X64:       # %bb.0:
 ; X64-NEXT:    pmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
 ; X64-NEXT:    pmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X64-NEXT:    pmovzxdq {{.*#+}} xmm2 = mem[0],zero,mem[1],zero
-; X64-NEXT:    pmovzxdq {{.*#+}} xmm3 = mem[0],zero,mem[1],zero
-; X64-NEXT:    movdqa %xmm0, %xmm4
-; X64-NEXT:    pmuludq %xmm3, %xmm4
-; X64-NEXT:    psrlq $32, %xmm0
-; X64-NEXT:    pmuludq %xmm3, %xmm0
-; X64-NEXT:    psllq $32, %xmm0
-; X64-NEXT:    paddq %xmm4, %xmm0
-; X64-NEXT:    movdqa %xmm1, %xmm3
-; X64-NEXT:    pmuludq %xmm2, %xmm3
-; X64-NEXT:    psrlq $32, %xmm1
 ; X64-NEXT:    pmuludq %xmm2, %xmm1
-; X64-NEXT:    psllq $32, %xmm1
-; X64-NEXT:    paddq %xmm3, %xmm1
+; X64-NEXT:    pmovzxdq {{.*#+}} xmm2 = mem[0],zero,mem[1],zero
+; X64-NEXT:    pmuludq %xmm2, %xmm0
 ; X64-NEXT:    retq
 ;
 ; X64-XOP-LABEL: mul_v4i64_zext_cross_bb:
 ; X64-XOP:       # %bb.0:
 ; X64-XOP-NEXT:    vpmovzxdq {{.*#+}} xmm0 = mem[0],zero,mem[1],zero
 ; X64-XOP-NEXT:    vpmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
 ; X64-XOP-NEXT:    vinsertf128 $1, %xmm0, %ymm1, %ymm0
 ; X64-XOP-NEXT:    vpmovzxdq {{.*#+}} xmm1 = mem[0],zero,mem[1],zero
 ; X64-XOP-NEXT:    vpmovzxdq {{.*#+}} xmm2 = mem[0],zero,mem[1],zero
 ; X64-XOP-NEXT:    vextractf128 $1, %ymm0, %xmm3
-; X64-XOP-NEXT:    vpmuludq %xmm2, %xmm3, %xmm4
-; X64-XOP-NEXT:    vpsrlq $32, %xmm3, %xmm3
 ; X64-XOP-NEXT:    vpmuludq %xmm2, %xmm3, %xmm2
-; X64-XOP-NEXT:    vpsllq $32, %xmm2, %xmm2
-; X64-XOP-NEXT:    vpaddq %xmm2, %xmm4, %xmm2
-; X64-XOP-NEXT:    vpmuludq %xmm1, %xmm0, %xmm3
-; X64-XOP-NEXT:    vpsrlq $32, %xmm0, %xmm0
 ; X64-XOP-NEXT:    vpmuludq %xmm1, %xmm0, %xmm0
-; X64-XOP-NEXT:    vpsllq $32, %xmm0, %xmm0
-; X64-XOP-NEXT:    vpaddq %xmm0, %xmm3, %xmm0
 ; X64-XOP-NEXT:    vinsertf128 $1, %xmm2, %ymm0, %ymm0
 ; X64-XOP-NEXT:    retq
 ;
 ; X64-AVX2-LABEL: mul_v4i64_zext_cross_bb:
 ; X64-AVX2:       # %bb.0:
 ; X64-AVX2-NEXT:    vpmovzxdq {{.*#+}} ymm0 = mem[0],zero,mem[1],zero,mem[2],zero,mem[3],zero
 ; X64-AVX2-NEXT:    vpmovzxdq {{.*#+}} ymm1 = mem[0],zero,mem[1],zero,mem[2],zero,mem[3],zero
-; X64-AVX2-NEXT:    vpmuludq %ymm1, %ymm0, %ymm2
-; X64-AVX2-NEXT:    vpsrlq $32, %ymm0, %ymm0
 ; X64-AVX2-NEXT:    vpmuludq %ymm1, %ymm0, %ymm0
-; X64-AVX2-NEXT:    vpsllq $32, %ymm0, %ymm0
-; X64-AVX2-NEXT:    vpaddq %ymm0, %ymm2, %ymm0
 ; X64-AVX2-NEXT:    retq
   %a = load <4 x i32>, <4 x i32>* %in
   %b = zext <4 x i32> %a to <4 x i64>
   br label %foo
 
 foo:
   %c = load <4 x i32>, <4 x i32>* %y
   %d = zext <4 x i32> %c to <4 x i64>
   %e = mul <4 x i64> %b, %d
   ret <4 x i64> %e
 }