[PowerPC] Use a small cleanup pass to remove VSX self copies

As explained in r204976, because of how the allocation of VSX registers
interacts with the call-lowering code, we sometimes end up generating self VSX
copies. Specifically, things like this:
  %VSL2<def> = COPY %F2, %VSL2<imp-use,kill>
(where %F2 is really a sub-register of %VSL2, and so this copy is a nop)

This adds a small cleanup pass to remove these prior to post-RA scheduling.

llvm-svn: 204980

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/PowerPC/vsx-self-copy.ll b/llvm/test/CodeGen/PowerPC/vsx-self-copy.ll
new file mode 100644
index 00000000000..23615ca10c1
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/vsx-self-copy.ll
@@ -0,0 +1,27 @@
+; RUN: llc -mcpu=pwr7 -mattr=+vsx < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+define double @takFP(double %x, double %y, double %z) #0 {
+entry:
+  br i1 undef, label %if.then, label %return
+
+if.then:                                          ; preds = %if.then, %entry
+  %x.tr16 = phi double [ %call, %if.then ], [ %x, %entry ]
+  %call = tail call double @takFP(double undef, double undef, double undef)
+  %call4 = tail call double @takFP(double undef, double %x.tr16, double undef)
+  %cmp = fcmp olt double undef, %call
+  br i1 %cmp, label %if.then, label %return
+
+return:                                           ; preds = %if.then, %entry
+  %z.tr.lcssa = phi double [ %z, %entry ], [ %call4, %if.then ]
+  ret double %z.tr.lcssa
+
+; CHECK: @takFP
+; CHECK-NOT: xxlor 0, 0, 0
+; CHECK: blr
+}
+
+attributes #0 = { nounwind readnone }
+attributes #1 = { nounwind }
+