instcombine: Migrate strncpy optimizations

This patch migrates the strncpy optimizations from the simplify-libcalls
pass into the instcombine library call simplifier.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167102 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 95 insertions, 0 deletions

diff --git a/test/Transforms/InstCombine/strncpy-1.ll b/test/Transforms/InstCombine/strncpy-1.ll
new file mode 100644
index 0000000000..3ce2b9b5ee
--- /dev/null
+++ b/test/Transforms/InstCombine/strncpy-1.ll
@@ -0,0 +1,95 @@
+; Test that the strncpy library call simplifier works correctly.
+;
+; RUN: opt < %s -instcombine -S | FileCheck %s
+
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+
+@hello = constant [6 x i8] c"hello\00"
+@null = constant [1 x i8] zeroinitializer
+@null_hello = constant [7 x i8] c"\00hello\00"
+@a = common global [32 x i8] zeroinitializer, align 1
+@b = common global [32 x i8] zeroinitializer, align 1
+
+declare i8* @strncpy(i8*, i8*, i32)
+declare i32 @puts(i8*)
+
+; Check a bunch of strncpy invocations together.
+
+define i32 @test_simplify1() {
+; CHECK: @test_simplify1
+; CHECK-NOT: call i8* @strncpy
+; CHECK: call i32 @puts
+  %target = alloca [1024 x i8]
+  %arg1 = getelementptr [1024 x i8]* %target, i32 0, i32 0
+  store i8 0, i8* %arg1
+
+  %arg2 = getelementptr [6 x i8]* @hello, i32 0, i32 0
+  %rslt1 = call i8* @strncpy(i8* %arg1, i8* %arg2, i32 6)
+
+  %arg3 = getelementptr [1 x i8]* @null, i32 0, i32 0
+  %rslt2 = call i8* @strncpy(i8* %rslt1, i8* %arg3, i32 42)
+
+  %arg4 = getelementptr [7 x i8]* @null_hello, i32 0, i32 0
+  %rslt3 = call i8* @strncpy(i8* %rslt2, i8* %arg4, i32 42)
+
+  call i32 @puts( i8* %rslt3 )
+  ret i32 0
+}
+
+; Check strncpy(x, "", y) -> memset(x, '\0', y, 1).
+
+define void @test_simplify2() {
+; CHECK: @test_simplify2
+  %dst = getelementptr [32 x i8]* @a, i32 0, i32 0
+  %src = getelementptr [1 x i8]* @null, i32 0, i32 0
+
+  call i8* @strncpy(i8* %dst, i8* %src, i32 32)
+; CHECK: call void @llvm.memset.p0i8.i32
+  ret void
+}
+
+; Check strncpy(x, y, 0) -> x.
+
+define i8* @test_simplify3() {
+; CHECK: @test_simplify3
+  %dst = getelementptr [32 x i8]* @a, i32 0, i32 0
+  %src = getelementptr [6 x i8]* @hello, i32 0, i32 0
+
+  %ret = call i8* @strncpy(i8* %dst, i8* %src, i32 0)
+  ret i8* %ret
+; CHECK: ret i8* getelementptr inbounds ([32 x i8]* @a, i32 0, i32 0)
+}
+
+; Check  strncpy(x, s, c) -> memcpy(x, s, c, 1) [s and c are constant].
+
+define void @test_simplify4() {
+; CHECK: @test_simplify4
+  %dst = getelementptr [32 x i8]* @a, i32 0, i32 0
+  %src = getelementptr [6 x i8]* @hello, i32 0, i32 0
+
+  call i8* @strncpy(i8* %dst, i8* %src, i32 6)
+; CHECK: call void @llvm.memcpy.p0i8.p0i8.i32
+  ret void
+}
+
+; Check cases that shouldn't be simplified.
+
+define void @test_no_simplify1() {
+; CHECK: @test_no_simplify1
+  %dst = getelementptr [32 x i8]* @a, i32 0, i32 0
+  %src = getelementptr [32 x i8]* @b, i32 0, i32 0
+
+  call i8* @strncpy(i8* %dst, i8* %src, i32 32)
+; CHECK: call i8* @strncpy
+  ret void
+}
+
+define void @test_no_simplify2() {
+; CHECK: @test_no_simplify2
+  %dst = getelementptr [32 x i8]* @a, i32 0, i32 0
+  %src = getelementptr [6 x i8]* @hello, i32 0, i32 0
+
+  call i8* @strncpy(i8* %dst, i8* %src, i32 8)
+; CHECK: call i8* @strncpy
+  ret void
+}