compiler: fix passing weirdly-padded structs to new goroutines

The values were stored in the passed object as the values itself (not
expanded like is common in the calling convention), and read back after
assuming they were expanded. This often works for simple parameters
(int, pointer, etc), but not for more complex parameters. Especially
when there's padding.

Found this while working on `//go:wasmexport`.

compiler/goroutine.go

@@ -49,7 +49,7 @@ func (b *builder) createGo(instr *ssa.Go) {
 	// Get all function parameters to pass to the goroutine.
 	var params []llvm.Value
 	for _, param := range instr.Call.Args {
-		params = append(params, b.getValue(param, getPos(instr)))
+		params = append(params, b.expandFormalParam(b.getValue(param, getPos(instr)))...)
 	}
 
 	var prefix string

compiler/testdata/goroutine-cortex-m-qemu-tasks.ll

@@ -3,8 +3,6 @@ source_filename = "goroutine.go"
 target datalayout = "e-m:e-p:32:32-Fi8-i64:64-v128:64:128-a:0:32-n32-S64"
 target triple = "thumbv7m-unknown-unknown-eabi"
 
-%runtime._string = type { ptr, i32 }
-
 @"main$string" = internal unnamed_addr constant [4 x i8] c"test", align 1
 
 ; Function Attrs: allockind("alloc,zeroed") allocsize(0)
@@ -150,12 +148,12 @@ define hidden void @main.startInterfaceMethod(ptr %itf.typecode, ptr %itf.value,
 entry:
   %0 = call align 4 dereferenceable(16) ptr @runtime.alloc(i32 16, ptr null, ptr undef) #9
   store ptr %itf.value, ptr %0, align 4
-  %1 = getelementptr inbounds { ptr, %runtime._string, ptr }, ptr %0, i32 0, i32 1
+  %1 = getelementptr inbounds { ptr, ptr, i32, ptr }, ptr %0, i32 0, i32 1
   store ptr @"main$string", ptr %1, align 4
-  %.repack1 = getelementptr inbounds { ptr, %runtime._string, ptr }, ptr %0, i32 0, i32 1, i32 1
-  store i32 4, ptr %.repack1, align 4
-  %2 = getelementptr inbounds { ptr, %runtime._string, ptr }, ptr %0, i32 0, i32 2
-  store ptr %itf.typecode, ptr %2, align 4
+  %2 = getelementptr inbounds { ptr, ptr, i32, ptr }, ptr %0, i32 0, i32 2
+  store i32 4, ptr %2, align 4
+  %3 = getelementptr inbounds { ptr, ptr, i32, ptr }, ptr %0, i32 0, i32 3
+  store ptr %itf.typecode, ptr %3, align 4
   %stacksize = call i32 @"internal/task.getGoroutineStackSize"(i32 ptrtoint (ptr @"interface:{Print:func:{basic:string}{}}.Print$invoke$gowrapper" to i32), ptr undef) #9
   call void @"internal/task.start"(i32 ptrtoint (ptr @"interface:{Print:func:{basic:string}{}}.Print$invoke$gowrapper" to i32), ptr nonnull %0, i32 %stacksize, ptr undef) #9
   ret void

compiler/testdata/goroutine-wasm-asyncify.ll

@@ -3,8 +3,6 @@ source_filename = "goroutine.go"
 target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-n32:64-S128-ni:1:10:20"
 target triple = "wasm32-unknown-wasi"
 
-%runtime._string = type { ptr, i32 }
-
 @"main$string" = internal unnamed_addr constant [4 x i8] c"test", align 1
 
 ; Function Attrs: allockind("alloc,zeroed") allocsize(0)
@@ -161,12 +159,12 @@ entry:
   %0 = call align 4 dereferenceable(16) ptr @runtime.alloc(i32 16, ptr null, ptr undef) #9
   call void @runtime.trackPointer(ptr nonnull %0, ptr nonnull %stackalloc, ptr undef) #9
   store ptr %itf.value, ptr %0, align 4
-  %1 = getelementptr inbounds { ptr, %runtime._string, ptr }, ptr %0, i32 0, i32 1
+  %1 = getelementptr inbounds { ptr, ptr, i32, ptr }, ptr %0, i32 0, i32 1
   store ptr @"main$string", ptr %1, align 4
-  %.repack1 = getelementptr inbounds { ptr, %runtime._string, ptr }, ptr %0, i32 0, i32 1, i32 1
-  store i32 4, ptr %.repack1, align 4
-  %2 = getelementptr inbounds { ptr, %runtime._string, ptr }, ptr %0, i32 0, i32 2
-  store ptr %itf.typecode, ptr %2, align 4
+  %2 = getelementptr inbounds { ptr, ptr, i32, ptr }, ptr %0, i32 0, i32 2
+  store i32 4, ptr %2, align 4
+  %3 = getelementptr inbounds { ptr, ptr, i32, ptr }, ptr %0, i32 0, i32 3
+  store ptr %itf.typecode, ptr %3, align 4
   call void @"internal/task.start"(i32 ptrtoint (ptr @"interface:{Print:func:{basic:string}{}}.Print$invoke$gowrapper" to i32), ptr nonnull %0, i32 65536, ptr undef) #9
   ret void
 }

testdata/goroutines.go

@@ -86,6 +86,10 @@ func main() {
 	testCond()
 
 	testIssue1790()
+
+	done := make(chan int)
+	go testPaddedParameters(paddedStruct{x: 5, y: 7}, done)
+	<-done
 }
 
 func acquire(m *sync.Mutex) {
@@ -243,3 +247,15 @@ func (f Foo) Wait() {
 	time.Sleep(time.Microsecond)
 	println("  ...waited")
 }
+
+type paddedStruct struct {
+	x uint8
+	_ [0]int64
+	y uint8
+}
+
+// Structs with interesting padding used to crash.
+func testPaddedParameters(s paddedStruct, done chan int) {
+	println("paddedStruct:", s.x, s.y)
+	close(done)
+}

testdata/goroutines.txt

@@ -26,3 +26,4 @@ called: Foo.Nowait
 called: Foo.Wait
   ...waited
 done with 'go on interface'
+paddedStruct: 5 7