[llvm] r357161 - [DAGCombiner] Fold truncate(build_vector(x, y)) -> build_vector(truncate(x), truncate(y))

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Thu Mar 28 04:34:21 2019
New Revision: 357161

URL: http://llvm.org/viewvc/llvm-project?rev=357161&view=rev
Log:
[DAGCombiner] Fold truncate(build_vector(x,y)) -> build_vector(truncate(x),truncate(y))

If scalar truncates are free, attempt to pre-truncate build_vectors source operands.

Only attempt to do this before legalization as we often end up with truncations/extensions during build_vector lowering.

Differential Revision: https://reviews.llvm.org/D59654

Modified:
    llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
    llvm/trunk/test/CodeGen/X86/bool-vector.ll
    llvm/trunk/test/CodeGen/X86/known-signbits-vector.ll

Modified: llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp?rev=357161&r1=357160&r2=357161&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/SelectionDAG/DAGCombiner.cpp Thu Mar 28 04:34:21 2019
@@ -9895,10 +9895,11 @@ SDValue DAGCombiner::visitZERO_EXTEND_VE
 SDValue DAGCombiner::visitTRUNCATE(SDNode *N) {
   SDValue N0 = N->getOperand(0);
   EVT VT = N->getValueType(0);
+  EVT SrcVT = N0.getValueType();
   bool isLE = DAG.getDataLayout().isLittleEndian();
 
   // noop truncate
-  if (N0.getValueType() == N->getValueType(0))
+  if (SrcVT == VT)
     return N0;
 
   // fold (truncate (truncate x)) -> (truncate x)
@@ -9999,6 +10000,19 @@ SDValue DAGCombiner::visitTRUNCATE(SDNod
     }
   }
 
+  // Attempt to pre-truncate BUILD_VECTOR sources.
+  if (N0.getOpcode() == ISD::BUILD_VECTOR && !LegalOperations &&
+      TLI.isTruncateFree(SrcVT.getScalarType(), VT.getScalarType())) {
+    SDLoc DL(N);
+    EVT SVT = VT.getScalarType();
+    SmallVector<SDValue, 8> TruncOps;
+    for (const SDValue &Op : N0->op_values()) {
+      SDValue TruncOp = DAG.getNode(ISD::TRUNCATE, DL, SVT, Op);
+      TruncOps.push_back(TruncOp);
+    }
+    return DAG.getBuildVector(VT, DL, TruncOps);
+  }
+
   // Fold a series of buildvector, bitcast, and truncate if possible.
   // For example fold
   //   (2xi32 trunc (bitcast ((4xi32)buildvector x, x, y, y) 2xi64)) to

Modified: llvm/trunk/test/CodeGen/X86/bool-vector.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/bool-vector.ll?rev=357161&r1=357160&r2=357161&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/bool-vector.ll (original)
+++ llvm/trunk/test/CodeGen/X86/bool-vector.ll Thu Mar 28 04:34:21 2019
@@ -77,17 +77,17 @@ define i32 @PR15215_good(<4 x i32> %inpu
 ; X32-NEXT:    pushl %esi
 ; X32-NEXT:    .cfi_def_cfa_offset 8
 ; X32-NEXT:    .cfi_offset %esi, -8
-; X32-NEXT:    movzbl {{[0-9]+}}(%esp), %eax
-; X32-NEXT:    andl $1, %eax
-; X32-NEXT:    movzbl {{[0-9]+}}(%esp), %ecx
-; X32-NEXT:    andl $1, %ecx
-; X32-NEXT:    movzbl {{[0-9]+}}(%esp), %edx
-; X32-NEXT:    andl $1, %edx
-; X32-NEXT:    movzbl {{[0-9]+}}(%esp), %esi
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %eax
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %ecx
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %edx
+; X32-NEXT:    movl {{[0-9]+}}(%esp), %esi
 ; X32-NEXT:    andl $1, %esi
-; X32-NEXT:    leal (%eax,%ecx,2), %eax
-; X32-NEXT:    leal (%eax,%edx,4), %eax
-; X32-NEXT:    leal (%eax,%esi,8), %eax
+; X32-NEXT:    andl $1, %edx
+; X32-NEXT:    andl $1, %ecx
+; X32-NEXT:    andl $1, %eax
+; X32-NEXT:    leal (%esi,%edx,2), %edx
+; X32-NEXT:    leal (%edx,%ecx,4), %ecx
+; X32-NEXT:    leal (%ecx,%eax,8), %eax
 ; X32-NEXT:    popl %esi
 ; X32-NEXT:    .cfi_def_cfa_offset 4
 ; X32-NEXT:    retl

Modified: llvm/trunk/test/CodeGen/X86/known-signbits-vector.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/known-signbits-vector.ll?rev=357161&r1=357160&r2=357161&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/known-signbits-vector.ll (original)
+++ llvm/trunk/test/CodeGen/X86/known-signbits-vector.ll Thu Mar 28 04:34:21 2019
@@ -36,17 +36,10 @@ define <4 x float> @signbits_sext_v4i64_
 ;
 ; X64-LABEL: signbits_sext_v4i64_sitofp_v4f32:
 ; X64:       # %bb.0:
-; X64-NEXT:    movslq %edi, %rax
-; X64-NEXT:    movslq %esi, %rsi
-; X64-NEXT:    movslq %edx, %rdx
-; X64-NEXT:    movslq %ecx, %rcx
-; X64-NEXT:    vmovq %rcx, %xmm0
-; X64-NEXT:    vmovq %rdx, %xmm1
-; X64-NEXT:    vpunpcklqdq {{.*#+}} xmm0 = xmm1[0],xmm0[0]
-; X64-NEXT:    vmovq %rsi, %xmm1
-; X64-NEXT:    vmovq %rax, %xmm2
-; X64-NEXT:    vpunpcklqdq {{.*#+}} xmm1 = xmm2[0],xmm1[0]
-; X64-NEXT:    vshufps {{.*#+}} xmm0 = xmm1[0,2],xmm0[0,2]
+; X64-NEXT:    vmovd %edi, %xmm0
+; X64-NEXT:    vpinsrd $1, %esi, %xmm0, %xmm0
+; X64-NEXT:    vpinsrd $2, %edx, %xmm0, %xmm0
+; X64-NEXT:    vpinsrd $3, %ecx, %xmm0, %xmm0
 ; X64-NEXT:    vcvtdq2ps %xmm0, %xmm0
 ; X64-NEXT:    retq
   %1 = sext i8 %a0 to i64