From 853a0858f33e6d27c1b3bc1a7cb29636a82e7663 Mon Sep 17 00:00:00 2001
From: Jack Whitman <jack-m5ml2@cs.york.ac.uk>
Date: Wed, 24 Jun 2009 21:22:46 -0700
Subject: ARM: Link register is trashed by non-executed branch and link
 operations.

---
 src/arch/arm/isa/formats/branch.isa | 8 ++++++++
 1 file changed, 8 insertions(+)

(limited to 'src/arch/arm/isa/formats/branch.isa')

diff --git a/src/arch/arm/isa/formats/branch.isa b/src/arch/arm/isa/formats/branch.isa
index b8fbb982d..95f4f14e1 100644
--- a/src/arch/arm/isa/formats/branch.isa
+++ b/src/arch/arm/isa/formats/branch.isa
@@ -38,8 +38,10 @@ def format Branch(code,*opt_flags) {{
     #Build Instruction Flags
     #Use Link & Likely Flags to Add Link/Condition Code
     inst_flags = ('IsDirectControl', )
+    linking = False
     for x in opt_flags:
         if x == 'Link':
+            linking = True
             code += 'LR = NPC;\n'
         else:
             inst_flags += (x, )
@@ -55,6 +57,8 @@ def format Branch(code,*opt_flags) {{
     icode += '  NPC = NPC + 4 + disp;\n'
     icode += '} else {\n'
     icode += '  NPC = NPC;\n'
+    if linking:
+        icode += '  LR = LR;\n'
     icode += '};\n'
 
     code = icode
@@ -70,8 +74,10 @@ def format BranchExchange(code,*opt_flags) {{
     #Build Instruction Flags
     #Use Link & Likely Flags to Add Link/Condition Code
     inst_flags = ('IsIndirectControl', )
+    linking = False
     for x in opt_flags:
         if x == 'Link':
+            linking = True
             code += 'LR = NPC;\n'
         else:
             inst_flags += (x, )
@@ -89,6 +95,8 @@ def format BranchExchange(code,*opt_flags) {{
     icode += '  NPC = Rm & 0xfffffffe; // Masks off bottom bit\n'
     icode += '} else {\n'
     icode += '  NPC = NPC;\n'
+    if linking:
+        icode += '  LR = LR;\n'
     icode += '};\n'
 
     code = icode
-- 
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