Fix art_quick_instrumentation_entry stub for x86/x86_64

Fixes bad stack offset for x86 where we read the return pc from an
incorrect location.

Fixes bad register for x86_64. The return pc is the 4th argument of
the called C function. It must be passed in rcx instead of r8 (which
is used for 5th argument).

Bug: 18170596
Change-Id: Idb521d2f6da415448fa61acf8b7d21076822830f
diff --git a/runtime/arch/x86/quick_entrypoints_x86.S b/runtime/arch/x86/quick_entrypoints_x86.S
index 69527ce..d471c67 100644
--- a/runtime/arch/x86/quick_entrypoints_x86.S
+++ b/runtime/arch/x86/quick_entrypoints_x86.S
@@ -1116,7 +1116,7 @@
     PUSH eax                      // Save eax which will be clobbered by the callee-save method.
     subl LITERAL(12), %esp        // Align stack.
     CFI_ADJUST_CFA_OFFSET(12)
-    pushl 40(%esp)                // Pass LR.
+    pushl FRAME_SIZE_REFS_AND_ARGS_CALLEE_SAVE-4+16(%esp)  // Pass LR.
     CFI_ADJUST_CFA_OFFSET(4)
     pushl %fs:THREAD_SELF_OFFSET  // Pass Thread::Current().
     CFI_ADJUST_CFA_OFFSET(4)
diff --git a/runtime/arch/x86_64/quick_entrypoints_x86_64.S b/runtime/arch/x86_64/quick_entrypoints_x86_64.S
index bed7238..9d3a8cc 100644
--- a/runtime/arch/x86_64/quick_entrypoints_x86_64.S
+++ b/runtime/arch/x86_64/quick_entrypoints_x86_64.S
@@ -1446,7 +1446,7 @@
     movq %rdi, %r12               // Preserve method pointer in a callee-save.
 
     movq %gs:THREAD_SELF_OFFSET, %rdx   // Pass thread.
-    movq FRAME_SIZE_REFS_AND_ARGS_CALLEE_SAVE-8(%rsp), %r8   // Pass return PC.
+    movq FRAME_SIZE_REFS_AND_ARGS_CALLEE_SAVE-8(%rsp), %rcx   // Pass return PC.
 
     call SYMBOL(artInstrumentationMethodEntryFromCode) // (Method*, Object*, Thread*, LR)