[SystemZ] Implement isLegalAddressingMode()

The loop optimizers were assuming that scales > 1 were OK.  I think this
is actually a bug in TargetLoweringBase::isLegalAddressingMode(),
since it seems to be trying to reject anything that isn't r+i or r+r,
but it has no default case for scales other than 0, 1 or 2.  Implementing
the hook for z means that z can no longer test any change there though.

llvm-svn: 187497

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/SystemZ/loop-01.ll b/llvm/test/CodeGen/SystemZ/loop-01.ll
new file mode 100644
index 00000000000..025a34eaf5c
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/loop-01.ll
@@ -0,0 +1,25 @@
+; Test loop tuning.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z10 | FileCheck %s
+
+; Test that strength reduction is applied to addresses with a scale factor,
+; but that indexed addressing can still be used.
+define void @f1(i32 *%dest, i32 %a) {
+; CHECK-LABEL: f1
+; CHECK-NOT: sllg
+; CHECK: st %r3, 0({{%r[1-5],%r[1-5]}})
+; CHECK: br %r14
+entry:
+  br label %loop
+
+loop:
+  %index = phi i64 [ 0, %entry ], [ %next, %loop ]
+  %ptr = getelementptr i32 *%dest, i64 %index
+  store i32 %a, i32 *%ptr
+  %next = add i64 %index, 1
+  %cmp = icmp ne i64 %next, 100
+  br i1 %cmp, label %loop, label %exit
+
+exit:
+  ret void
+}