[SystemZ] Improve optimizeCompareZero()

More conversions to load-and-test can be made with this patch by adding a
forward search in optimizeCompareZero().

Review: Ulrich Weigand
https://reviews.llvm.org/D38076

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313877 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 44 insertions, 0 deletions

diff --git a/test/CodeGen/SystemZ/fp-cmp-07.mir b/test/CodeGen/SystemZ/fp-cmp-07.mir
new file mode 100644
index 00000000000..1d766fe300a
--- /dev/null
+++ b/test/CodeGen/SystemZ/fp-cmp-07.mir
@@ -0,0 +1,44 @@
+# RUN: llc -mtriple=s390x-linux-gnu -mcpu=z10 -no-integrated-as -start-after=block-placement %s -o - | FileCheck %s
+# Test that LTEBR is used without an unnecessary LER
+
+--- |
+  define float @f15(float %val, float %dummy, float* %dest) {
+  entry:
+    call void asm sideeffect "blah $0", "{f2}"(float %val)
+    %cmp = fcmp olt float %val, 0.000000e+00
+    br i1 %cmp, label %exit, label %store
+
+  store:                                            ; preds = %entry
+    store float %val, float* %dest
+    br label %exit
+
+  exit:                                             ; preds = %store, %entry
+    ret float %val
+  }
+
+...
+
+# CHECK: ltebr %f2, %f0
+
+---
+name:            f15
+tracksRegLiveness: true
+liveins:
+  - { reg: '%f0s', virtual-reg: '' }
+  - { reg: '%r2d', virtual-reg: '' }
+body:             |
+  bb.0.entry:
+    liveins: %f0s, %r2d
+
+    LTEBRCompare %f0s, %f0s, implicit-def %cc
+    %f2s = LER %f0s
+    INLINEASM $"blah $0", 1, 9, %f2s
+    CondReturn 15, 4, implicit %f0s, implicit %cc
+
+  bb.1.store:
+    liveins: %f0s, %r2d
+
+    STE %f0s, killed %r2d, 0, _ :: (store 4 into %ir.dest)
+    Return implicit %f0s
+
+...