[LICM] Add tests for future hoisting of fence instructions [NFC]

The main interesting case is a fence in an otherwise dead loop or one containing only arithmetic.  This can happen as a result of DSE or other transforms from seemingly reasonable initial IR.  



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@339310 91177308-0d34-0410-b5e6-96231b3b80d8

Author: preames

test/Transforms/LICM/fence.ll

@@ -0,0 +1,118 @@
+; RUN: opt -licm -basicaa < %s -S | FileCheck %s
+; RUN: opt -aa-pipeline=basic-aa -passes='require<aa>,require<targetir>,require<scalar-evolution>,require<opt-remark-emit>,loop(licm)' < %s -S | FileCheck %s
+
+define void @test1(i64 %n) {
+; CHECK-LABEL: @test1
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  fence release
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+
+define void @test2(i64 %n) {
+; CHECK-LABEL: @test2
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  fence acquire
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+
+define void @test3(i64 %n) {
+; CHECK-LABEL: @test3
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  fence acq_rel
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+
+define void @test4(i64 %n) {
+; CHECK-LABEL: @test4
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  fence seq_cst
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+
+define void @testneg1(i64 %n, i64* %p) {
+; CHECK-LABEL: @testneg1
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  store i64 %iv, i64* %p
+  fence release
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+
+define void @testneg2(i64* %p) {
+; CHECK-LABEL: @testneg2
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  fence acquire
+  %n = load i64, i64* %p
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+
+define void @testfp1(i64 %n, i64* %p) {
+; CHECK-LABEL: @testfp1
+; CHECK-LABEL: loop:
+; CHECK: fence
+entry:
+  br label %loop
+loop:
+  %iv = phi i64 [0, %entry], [%iv.next, %loop]
+  fence release
+  fence release
+  %iv.next = add i64 %iv, 1
+  %test = icmp slt i64 %iv, %n
+  br i1 %test, label %loop, label %exit
+exit:
+  ret void
+}
+