runtime: precisely scan Wasm globals

transform/testdata/gc-globals-avr.ll

@@ -0,0 +1,12 @@
+target datalayout = "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8:16-a:8"
+target triple = "avr-unknown-unknown"
+
+%entry = type { i8, ptr }
+
+@table = global [4 x %entry] zeroinitializer
+
+declare i16 @runtime.gcGlobalRootCount()
+
+declare ptr @runtime.gcGlobalRoot(i16)
+
+declare i16 @runtime.gcGlobalRootSize(i16)

transform/testdata/gc-globals-avr.out.ll

@@ -0,0 +1,28 @@
+target datalayout = "e-P1-p:16:8-i8:8-i16:8-i32:8-i64:8-f32:8-f64:8-n8:16-a:8"
+target triple = "avr-unknown-unknown"
+
+%entry = type { i8, ptr }
+
+@table = global [4 x %entry] zeroinitializer
+@runtime.gcGlobalRoots = internal constant [4 x { ptr, i16 }] [{ ptr, i16 } { ptr getelementptr (i8, ptr @table, i16 1), i16 2 }, { ptr, i16 } { ptr getelementptr (i8, ptr @table, i16 4), i16 2 }, { ptr, i16 } { ptr getelementptr (i8, ptr @table, i16 7), i16 2 }, { ptr, i16 } { ptr getelementptr (i8, ptr @table, i16 10), i16 2 }]
+
+define i16 @runtime.gcGlobalRootCount() addrspace(1) {
+entry:
+  ret i16 4
+}
+
+define ptr @runtime.gcGlobalRoot(i16 %0) addrspace(1) {
+entry:
+  %1 = getelementptr inbounds [4 x { ptr, i16 }], ptr @runtime.gcGlobalRoots, i32 0, i16 %0
+  %2 = getelementptr inbounds nuw { ptr, i16 }, ptr %1, i32 0, i32 0
+  %3 = load ptr, ptr %2, align 1
+  ret ptr %3
+}
+
+define i16 @runtime.gcGlobalRootSize(i16 %0) addrspace(1) {
+entry:
+  %1 = getelementptr inbounds [4 x { ptr, i16 }], ptr @runtime.gcGlobalRoots, i32 0, i16 %0
+  %2 = getelementptr inbounds nuw { ptr, i16 }, ptr %1, i32 0, i32 1
+  %3 = load i16, ptr %2, align 1
+  ret i16 %3
+}

transform/testdata/gc-stackslots.ll

@@ -5,11 +5,22 @@ target triple = "wasm32-unknown-unknown-wasm"
 @someGlobal = global i8 3
 @ptrGlobal = global ptr null
 @arrGlobal = global [8 x i8] zeroinitializer
+@structGlobal = global {ptr, i32, [2 x ptr]} zeroinitializer
+@ptrArrayGlobal = global [8 x ptr] zeroinitializer
+@constantPtrGlobal = constant ptr @someGlobal
 
 declare void @runtime.trackPointer(ptr nocapture readonly)
 
 declare noalias nonnull ptr @runtime.alloc(i32, ptr)
 
+declare i32 @runtime.gcGlobalRootCount()
+
+declare ptr @runtime.gcGlobalRoot(i32)
+
+declare i32 @runtime.gcGlobalRootSize(i32)
+
+declare ptr @runtime.gcGlobalRootValues()
+
 ; Generic function that returns a pointer (that must be tracked).
 define ptr @getPointer() {
     ret ptr @someGlobal

transform/testdata/gc-stackslots.out.ll

@@ -5,11 +5,42 @@ target triple = "wasm32-unknown-unknown-wasm"
 @someGlobal = global i8 3
 @ptrGlobal = global ptr null
 @arrGlobal = global [8 x i8] zeroinitializer
+@structGlobal = global { ptr, i32, [2 x ptr] } zeroinitializer
+@ptrArrayGlobal = global [8 x ptr] zeroinitializer
+@constantPtrGlobal = constant ptr @someGlobal
+@runtime.gcGlobalRoots = internal constant [4 x { ptr, i32 }] [{ ptr, i32 } { ptr @ptrGlobal, i32 4 }, { ptr, i32 } { ptr @structGlobal, i32 4 }, { ptr, i32 } { ptr getelementptr (i8, ptr @structGlobal, i32 8), i32 8 }, { ptr, i32 } { ptr @ptrArrayGlobal, i32 32 }]
+@runtime.gcGlobalRootValueArray = internal global [12 x i32] zeroinitializer
 
 declare void @runtime.trackPointer(ptr nocapture readonly)
 
 declare noalias nonnull ptr @runtime.alloc(i32, ptr)
 
+define i32 @runtime.gcGlobalRootCount() {
+entry:
+  ret i32 4
+}
+
+define ptr @runtime.gcGlobalRoot(i32 %0) {
+entry:
+  %1 = getelementptr inbounds [4 x { ptr, i32 }], ptr @runtime.gcGlobalRoots, i32 0, i32 %0
+  %2 = getelementptr inbounds nuw { ptr, i32 }, ptr %1, i32 0, i32 0
+  %3 = load ptr, ptr %2, align 4
+  ret ptr %3
+}
+
+define i32 @runtime.gcGlobalRootSize(i32 %0) {
+entry:
+  %1 = getelementptr inbounds [4 x { ptr, i32 }], ptr @runtime.gcGlobalRoots, i32 0, i32 %0
+  %2 = getelementptr inbounds nuw { ptr, i32 }, ptr %1, i32 0, i32 1
+  %3 = load i32, ptr %2, align 4
+  ret i32 %3
+}
+
+define ptr @runtime.gcGlobalRootValues() {
+entry:
+  ret ptr @runtime.gcGlobalRootValueArray
+}
+
 define ptr @getPointer() {
   ret ptr @someGlobal
 }