[SystemZ] Use CLC and IPM to implement memcmp

For now this is restricted to fixed-length comparisons with a length
in the range [1, 256], as for memcpy() and MVC.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@188163 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 134 insertions, 0 deletions

diff --git a/test/CodeGen/SystemZ/memcmp-01.ll b/test/CodeGen/SystemZ/memcmp-01.ll
new file mode 100644
index 0000000..3747769
--- /dev/null
+++ b/test/CodeGen/SystemZ/memcmp-01.ll
@@ -0,0 +1,134 @@
+; Test memcmp using CLC.
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu | FileCheck %s
+
+declare signext i32 @memcmp(i8 *%src1, i8 *%src2, i64 %size)
+
+; Zero-length comparisons should be optimized away.
+define i32 @f1(i8 *%src1, i8 *%src2) {
+; CHECK-LABEL: f1:
+; CHECK: lhi %r2, 0
+; CHECK: br %r14
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 0)
+  ret i32 %res
+}
+
+; Check a case where the result is used as an integer.
+define i32 @f2(i8 *%src1, i8 *%src2) {
+; CHECK-LABEL: f2:
+; CHECK: clc 0(2,%r2), 0(%r3)
+; CHECK: ipm %r2
+; CHECK: sll %r2, 2
+; CHECK: sra %r2, 30
+; CHECK: br %r14
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 2)
+  ret i32 %res
+}
+
+; Check a case where the result is tested for equality.
+define void @f3(i8 *%src1, i8 *%src2, i32 *%dest) {
+; CHECK-LABEL: f3:
+; CHECK: clc 0(3,%r2), 0(%r3)
+; CHECK-NEXT: je {{\..*}}
+; CHECK: br %r14
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 3)
+  %cmp = icmp eq i32 %res, 0
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 0, i32 *%dest
+  br label %exit
+
+exit:
+  ret void
+}
+
+; Check a case where the result is tested for inequality.
+define void @f4(i8 *%src1, i8 *%src2, i32 *%dest) {
+; CHECK-LABEL: f4:
+; CHECK: clc 0(4,%r2), 0(%r3)
+; CHECK-NEXT: jlh {{\..*}}
+; CHECK: br %r14
+entry:
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 4)
+  %cmp = icmp ne i32 %res, 0
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 0, i32 *%dest
+  br label %exit
+
+exit:
+  ret void
+}
+
+; Check a case where the result is tested via slt.
+define void @f5(i8 *%src1, i8 *%src2, i32 *%dest) {
+; CHECK-LABEL: f5:
+; CHECK: clc 0(5,%r2), 0(%r3)
+; CHECK-NEXT: jl {{\..*}}
+; CHECK: br %r14
+entry:
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 5)
+  %cmp = icmp slt i32 %res, 0
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 0, i32 *%dest
+  br label %exit
+
+exit:
+  ret void
+}
+
+; Check a case where the result is tested for sgt.
+define void @f6(i8 *%src1, i8 *%src2, i32 *%dest) {
+; CHECK-LABEL: f6:
+; CHECK: clc 0(6,%r2), 0(%r3)
+; CHECK-NEXT: jh {{\..*}}
+; CHECK: br %r14
+entry:
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 6)
+  %cmp = icmp sgt i32 %res, 0
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 0, i32 *%dest
+  br label %exit
+
+exit:
+  ret void
+}
+
+; Check the upper end of the CLC range.  Here the result is used both as
+; an integer and for branching, but it's better to branch on the result
+; of the SRA.
+define i32 @f7(i8 *%src1, i8 *%src2, i32 *%dest) {
+; CHECK-LABEL: f7:
+; CHECK: clc 0(256,%r2), 0(%r3)
+; CHECK: ipm %r2
+; CHECK: sll %r2, 2
+; CHECK: sra %r2, 30
+; CHECK: jl {{.L*}}
+; CHECK: br %r14
+entry:
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 256)
+  %cmp = icmp slt i32 %res, 0
+  br i1 %cmp, label %exit, label %store
+
+store:
+  store i32 0, i32 *%dest
+  br label %exit
+
+exit:
+  ret i32 %res
+}
+
+; 257 bytes is too big for a single CLC.  For now expect a call instead.
+define i32 @f8(i8 *%src1, i8 *%src2) {
+; CHECK-LABEL: f8:
+; CHECK: brasl %r14, memcmp@PLT
+; CHECK: br %r14
+  %res = call i32 @memcmp(i8 *%src1, i8 *%src2, i64 257)
+  ret i32 %res
+}