transform: add byte slice string length tests

Author: jakebailey

transform/rtcalls_test.go

@@ -36,3 +36,10 @@ func TestOptimizeStringFromBytesStringLess(t *testing.T) {
 		transform.OptimizeStringFromBytes(mod)
 	})
 }
+
+func TestOptimizeStringFromBytesLen(t *testing.T) {
+	t.Parallel()
+	testTransform(t, "testdata/stringfrombytes-len", func(mod llvm.Module) {
+		// TODO: optimize the []byte-to-string conversion away.
+	})
+}

transform/testdata/stringfrombytes-len.ll

@@ -0,0 +1,31 @@
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7m-none-eabi"
+
+%runtime._string = type { ptr, i32 }
+
+declare %runtime._string @runtime.stringFromBytes(ptr, i32, i32, ptr)
+
+declare void @runtime.trackPointer(ptr, ptr, ptr)
+
+declare void @useString(ptr, i32)
+
+define i32 @main.stringFromBytesLen(ptr %a.data, i32 %a.len, i32 %a.cap, ptr %context) {
+entry:
+  %stackalloc = alloca i8, align 1
+  %0 = call %runtime._string @runtime.stringFromBytes(ptr %a.data, i32 %a.len, i32 %a.cap, ptr undef)
+  %1 = extractvalue %runtime._string %0, 0
+  call void @runtime.trackPointer(ptr %1, ptr %stackalloc, ptr undef)
+  %2 = extractvalue %runtime._string %0, 1
+  %len = extractvalue %runtime._string %0, 1
+  ret i32 %len
+}
+
+define i32 @main.keepStringConversion(ptr %a.data, i32 %a.len, i32 %a.cap, ptr %context) {
+entry:
+  %0 = call %runtime._string @runtime.stringFromBytes(ptr %a.data, i32 %a.len, i32 %a.cap, ptr undef)
+  %1 = extractvalue %runtime._string %0, 0
+  %2 = extractvalue %runtime._string %0, 1
+  call void @useString(ptr %1, i32 %2)
+  %len = extractvalue %runtime._string %0, 1
+  ret i32 %len
+}

transform/testdata/stringfrombytes-len.out.ll

@@ -0,0 +1,31 @@
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7m-none-eabi"
+
+%runtime._string = type { ptr, i32 }
+
+declare %runtime._string @runtime.stringFromBytes(ptr, i32, i32, ptr)
+
+declare void @runtime.trackPointer(ptr, ptr, ptr)
+
+declare void @useString(ptr, i32)
+
+define i32 @main.stringFromBytesLen(ptr %a.data, i32 %a.len, i32 %a.cap, ptr %context) {
+entry:
+  %stackalloc = alloca i8, align 1
+  %0 = call %runtime._string @runtime.stringFromBytes(ptr %a.data, i32 %a.len, i32 %a.cap, ptr undef)
+  %1 = extractvalue %runtime._string %0, 0
+  call void @runtime.trackPointer(ptr %1, ptr %stackalloc, ptr undef)
+  %2 = extractvalue %runtime._string %0, 1
+  %len = extractvalue %runtime._string %0, 1
+  ret i32 %len
+}
+
+define i32 @main.keepStringConversion(ptr %a.data, i32 %a.len, i32 %a.cap, ptr %context) {
+entry:
+  %0 = call %runtime._string @runtime.stringFromBytes(ptr %a.data, i32 %a.len, i32 %a.cap, ptr undef)
+  %1 = extractvalue %runtime._string %0, 0
+  %2 = extractvalue %runtime._string %0, 1
+  call void @useString(ptr %1, i32 %2)
+  %len = extractvalue %runtime._string %0, 1
+  ret i32 %len
+}