---

yaml
---
r: 6574
b: refs/heads/master
c: 52d7dc5
h: refs/heads/master
v: v3

Author: brson

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: a69eab16ec3435bd505a7dafcb9a82b5eace49a2
+refs/heads/master: 52d7dc5e0a218f1495da2057ac064811853a4c9c

trunk/src/rt/arch/i386/morestack.S

@@ -25,11 +25,6 @@
 #endif
 #endif
 
-// FIXME: Future LLVM patches remove these 8 alignment bytes from
-// the function prologue in order to match gcc's behavior
-#define ALIGNMENT 8
-#define RETURN_OFFSET   7
-
 .globl UPCALL_NEW_STACK
 .globl UPCALL_DEL_STACK
 .globl RUST_GET_TASK
@@ -57,17 +52,17 @@ MORESTACK:
 
 	// FIXME (1226): main is compiled with the split-stack prologue,
 	// causing it to call __morestack, so we have to jump back out
-	subl $20,%esp
+	subl $28,%esp
 	calll RUST_GET_TASK
 	testl %eax,%eax
 	jz .L$bail
 
 	// The arguments to rust_new_stack2
-	movl 32(%esp),%eax  // Size of stack arguments
+	movl 40(%esp),%eax  // Size of stack arguments
 	movl %eax,16(%esp)
-	leal 40+ALIGNMENT(%esp),%eax // Address of stack arguments
+	leal 48(%esp),%eax // Address of stack arguments
 	movl %eax,12(%esp)
-	movl 28(%esp),%eax // The amount of stack needed
+	movl 36(%esp),%eax // The amount of stack needed
 	movl %eax,8(%esp)
 
 #ifdef __APPLE__
@@ -83,8 +78,8 @@ MORESTACK:
 	movl %eax,(%esp)
 	call UPCALL_CALL_C
 
-	movl 24(%esp),%edx          // Grab the return pointer.
-	addl $RETURN_OFFSET,%edx    // Skip past the `add esp,4` and the `ret`.
+	movl 32(%esp),%edx          // Grab the return pointer.
+	inc  %edx    // Skip past the ret instruction in the parent fn
 
 	movl %eax,%esp          // Switch stacks.
 	call *%edx             // Re-enter the function that called us.
@@ -95,6 +90,8 @@ MORESTACK:
 	// Switch back to the rust stack
 	movl %ebp, %esp
 
+	subl $8, %esp // Alignment
+
 #ifdef __APPLE__
 	call 1f
 1:	popl %ebx
@@ -107,17 +104,17 @@ MORESTACK:
 	pushl $0
 	call UPCALL_CALL_C
 
-	addl $8,%esp
+	addl $16,%esp
 	popl %ebp
 	retl $8
 
 .L$bail:
-	movl 24(%esp),%edx
-	addl $RETURN_OFFSET,%edx
+	movl 32(%esp),%edx
+	inc %edx
 
-	addl $20, %esp
+	addl $28, %esp
 	popl %ebp
-	addl $4+8+ALIGNMENT,%esp
+	addl $4+8,%esp
 
 	jmpl *%edx
 

trunk/src/rt/rust_task.cpp

@@ -598,10 +598,17 @@ rust_task::del_stack() {
 
 void
 rust_task::record_stack_limit() {
-    // FIXME: Future LLVM patches expect us to add an additional 256 bytes
-    // here so that, if the frame size is < 256 it can generate the
-    // comparison against esp directly, instead of some offset from esp
-    record_sp(stk->data + RED_ZONE_SIZE);
+    // The function prolog compares the amount of stack needed to the end of
+    // the stack. As an optimization, when the frame size is less than 256
+    // bytes, it will simply compare %esp to to the stack limit instead of
+    // subtracting the frame size. As a result we need our stack limit to
+    // account for those 256 bytes.
+    const unsigned LIMIT_OFFSET = 256;
+    A(sched,
+      (uintptr_t)stk->limit - RED_ZONE_SIZE
+      - (uintptr_t)stk->data >= LIMIT_OFFSET,
+      "Stack size must be greater than LIMIT_OFFSET");
+    record_sp(stk->data + LIMIT_OFFSET + RED_ZONE_SIZE);
 }
 //
 // Local Variables: