[SystemZ] Use MVC to spill loads and stores

Try to use MVC when spilling the destination of a simple load or the source
of a simple store.  As explained in the comment, this doesn't yet handle
the case where the load or store location is also a frame index, since
that could lead to two simultaneous scavenger spills, something the
backend can't handle yet.  spill-02.py tests that this restriction kicks in,
but unfortunately I've not yet found a case that would fail without it.
The volatile trick I used for other scavenger tests doesn't work here
because we can't use MVC for volatile accesses anyway.

I'm planning on relaxing the restriction later, hopefully with a test
that does trigger the problem...

Tests @f8 and @f9 also showed that L(G)RL and ST(G)RL were wrongly
classified as SimpleBDX{Load,Store}.  It wouldn't be easy to test for
that bug separately, which is why I didn't split out the fix as a
separate patch.

llvm-svn: 185434

1 files changed, 46 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/SystemZ/Large/spill-02.py b/llvm/test/CodeGen/SystemZ/Large/spill-02.py
new file mode 100644
index 00000000000..0eba3edecb7
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/Large/spill-02.py
@@ -0,0 +1,46 @@
+# Test cases where we spill from one frame index to another, both of which
+# would be out of range of MVC.  At present we don't use MVC in this case.
+# RUN: python %s | llc -mtriple=s390x-linux-gnu | FileCheck %s
+
+# There are 8 usable call-saved GPRs.  The first 160 bytes of the frame
+# are needed for the ABI call frame, and a further 8 bytes are needed
+# for the emergency spill slot.  That means we will have at least one
+# out-of-range slot if:
+#
+#    count == (4096 - 168) / 8 + 8 + 1 == 500
+#
+# Add in some extra just to be sure.
+#
+# CHECK: f1:
+# CHECK-NOT: mvc
+# CHECK: br %r14
+count = 510
+
+print 'declare void @foo(i64 *%base0, i64 *%base1)'
+print ''
+print 'define void @f1() {'
+
+for i in range(2):
+    print '  %%alloc%d = alloca [%d x i64]' % (i, count / 2)
+    print ('  %%base%d = getelementptr [%d x i64] * %%alloc%d, i64 0, i64 0'
+           % (i, count / 2, i))
+
+print '  call void @foo(i64 *%base0, i64 *%base1)'
+print ''
+
+for i in range(count):
+    print '  %%ptr%d = getelementptr i64 *%%base%d, i64 %d' % (i, i % 2, i / 2)
+    print '  %%val%d = load i64 *%%ptr%d' % (i, i)
+    print ''
+
+print '  call void @foo(i64 *%base0, i64 *%base1)'
+print ''
+
+for i in range (count):
+    print '  store i64 %%val%d, i64 *%%ptr%d' % (i, i)
+
+print ''
+print '  call void @foo(i64 *%base0, i64 *%base1)'
+print ''
+print '  ret void'
+print '}'