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authorJack Whitman <jack-m5ml2@cs.york.ac.uk>2009-06-24 21:22:46 -0700
committerJack Whitman <jack-m5ml2@cs.york.ac.uk>2009-06-24 21:22:46 -0700
commit853a0858f33e6d27c1b3bc1a7cb29636a82e7663 (patch)
tree7a01f9cecf1546ea2ab7f15e8026829c45c67be8 /src/arch/arm
parent6dd42728040751dec6f83d7bd89a2b33f2339fc6 (diff)
downloadgem5-853a0858f33e6d27c1b3bc1a7cb29636a82e7663.tar.xz
ARM: Link register is trashed by non-executed branch and link operations.
Diffstat (limited to 'src/arch/arm')
-rw-r--r--src/arch/arm/isa/decoder.isa4
-rw-r--r--src/arch/arm/isa/formats/branch.isa8
2 files changed, 10 insertions, 2 deletions
diff --git a/src/arch/arm/isa/decoder.isa b/src/arch/arm/isa/decoder.isa
index af325b57a..20f5b99f0 100644
--- a/src/arch/arm/isa/decoder.isa
+++ b/src/arch/arm/isa/decoder.isa
@@ -246,7 +246,7 @@ decode COND_CODE default Unknown::unknown() {
}});
}
0x3: decode OPCODE_24_21 {
- 0x9: BranchExchange::blx({{ LR = NPC; }});
+ 0x9: BranchExchange::blx({{ }}, Link);
}
}
}
@@ -661,7 +661,7 @@ decode COND_CODE default Unknown::unknown() {
0x5: decode OPCODE_24 {
// Branch (and Link) Instructions
0: Branch::b({{ }});
- 1: Branch::bl({{ LR = NPC; }});
+ 1: Branch::bl({{ }}, Link);
}
0x6: decode CPNUM {
0x1: decode PUNWL {
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