[PowerPC] Don't run BV DAG Combine before legalization if it assumes legal types

When trying to combine a DAG that builds a vector out of sign-extensions of
vector extracts, the code assumes legal input types. Due to that, we have to
disable this combine prior to legalization.
In some cases, the DAG will look slightly different after legalization so
account for that in the matching code.

This is a fix for https://bugs.llvm.org/show_bug.cgi?id=38087

Differential Revision: https://reviews.llvm.org/D49080

llvm-svn: 339769

1 files changed, 10 insertions, 3 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index d1f23e6642b..b5bdf47ce37 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -11996,10 +11996,15 @@ static SDValue combineBVOfVecSExt(SDNode *N, SelectionDAG &DAG) {
   auto isSExtOfVecExtract = [&](SDValue Op) -> bool {
     if (!Op)
       return false;
-    if (Op.getOpcode() != ISD::SIGN_EXTEND)
+    if (Op.getOpcode() != ISD::SIGN_EXTEND &&
+        Op.getOpcode() != ISD::SIGN_EXTEND_INREG)
       return false;
 
+    // A SIGN_EXTEND_INREG might be fed by an ANY_EXTEND to produce a value
+    // of the right width.
     SDValue Extract = Op.getOperand(0);
+    if (Extract.getOpcode() == ISD::ANY_EXTEND)
+      Extract = Extract.getOperand(0);
     if (Extract.getOpcode() != ISD::EXTRACT_VECTOR_ELT)
       return false;
 
@@ -12087,8 +12092,10 @@ SDValue PPCTargetLowering::DAGCombineBuildVector(SDNode *N,
     return Reduced;
 
   // If we're building a vector out of extended elements from another vector
-  // we have P9 vector integer extend instructions.
-  if (Subtarget.hasP9Altivec()) {
+  // we have P9 vector integer extend instructions. The code assumes legal
+  // input types (i.e. it can't handle things like v4i16) so do not run before
+  // legalization.
+  if (Subtarget.hasP9Altivec() && !DCI.isBeforeLegalize()) {
     Reduced = combineBVOfVecSExt(N, DAG);
     if (Reduced)
       return Reduced;