GlobalISel: Combine g_extract with g_merge_values

Try to use the underlying source registers.

This enables legalization in more cases where some irregular
operations are widened and others narrowed.

This seems to make the test_combines_2 AArch64 test worse, since the
MERGE_VALUES has multiple uses. Since this should be required for
legalization, a hasOneUse check is probably inappropriate (or maybe
should only be used if the merge is legal?).

llvm-svn: 353121

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp b/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp
index b96827bd857..02fa4d12038 100644
--- a/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/Legalizer.cpp
@@ -76,6 +76,7 @@ static bool isArtifact(const MachineInstr &MI) {
   case TargetOpcode::G_UNMERGE_VALUES:
   case TargetOpcode::G_CONCAT_VECTORS:
   case TargetOpcode::G_BUILD_VECTOR:
+  case TargetOpcode::G_EXTRACT:
     return true;
   }
 }