[PowerPC] Avoid VSX FMA mutate when killed product reg = addend reg

With VSX enabled, test/CodeGen/PowerPC/recipest.ll exposes a bug in
the FMA mutation pass.  If we have a situation where a killed product
register is the same register as the FMA target, such as:

   %vreg5<def,tied1> = XSNMSUBADP %vreg5<tied0>, %vreg11, %vreg5,
                       %RM<imp-use>; VSFRC:%vreg5 F8RC:%vreg11 

then the substitution makes no sense.  We end up getting a crash when
we try to extend the interval associated with the killed product
register, as there is already a live range for %vreg5 there.  This
patch just disables the mutation under those circumstances.

Since recipest.ll generates different code with VMX enabled, I've
modified that test to use -mattr=-vsx.  I've borrowed the code from
that test that exposed the bug and placed it in fma-mutate.ll, where
it tests several mutation opportunities including the "bad" one.

llvm-svn: 220290

1 files changed, 21 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/PowerPC/fma-mutate.ll b/llvm/test/CodeGen/PowerPC/fma-mutate.ll
new file mode 100644
index 00000000000..1a391f4c230
--- /dev/null
+++ b/llvm/test/CodeGen/PowerPC/fma-mutate.ll
@@ -0,0 +1,21 @@
+; Test several VSX FMA mutation opportunities.  The first one isn't a
+; reasonable transformation because the killed product register is the
+; same as the FMA target register.  The second one is legal.  The third
+; one doesn't fit the feeding-copy pattern.
+
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr7 -enable-unsafe-fp-math -mattr=+vsx | FileCheck %s
+target datalayout = "E-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-f128:128:128-v128:128:128-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+declare double @llvm.sqrt.f64(double)
+
+define double @foo3(double %a) nounwind {
+  %r = call double @llvm.sqrt.f64(double %a)
+  ret double %r
+
+; CHECK: @foo3
+; CHECK: xsnmsubadp [[REG:[0-9]+]], {{[0-9]+}}, [[REG]]
+; CHECK: xsmaddmdp
+; CHECK: xsmaddadp
+}
+