[AArch64][GlobalISel] Don't do extending loads combine for non-pow-2 types.

Since non-pow-2 types are going to get split up into multiple loads anyway,
don't do the [SZ]EXTLOAD combine for those and save us trouble later in
legalization.

llvm-svn: 358458

1 files changed, 5 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
index 2eab5748980..4a4431643b0 100644
--- a/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/CombinerHelper.cpp
@@ -194,6 +194,11 @@ bool CombinerHelper::matchCombineExtendingLoads(MachineInstr &MI,
   if (LoadValueTy.getSizeInBits() < 8)
     return false;
 
+  // For non power-of-2 types, they will very likely be legalized into multiple
+  // loads. Don't bother trying to match them into extending loads.
+  if (!isPowerOf2_32(LoadValueTy.getSizeInBits()))
+    return false;
+
   // Find the preferred type aside from the any-extends (unless it's the only
   // one) and non-extending ops. We'll emit an extending load to that type and
   // and emit a variant of (extend (trunc X)) for the others according to the