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authorAli Saidi <Ali.Saidi@ARM.com>2011-03-17 19:20:20 -0500
committerAli Saidi <Ali.Saidi@ARM.com>2011-03-17 19:20:20 -0500
commit53ab306acc725670138d6f65ae2dbef241ac49a3 (patch)
treea8be451263e5166c04c2fc60dfd3bbba200e71a6 /src/arch/arm/insts
parent4c7a7796ade354a41fac9b4c14d4715cbe9e78c4 (diff)
downloadgem5-53ab306acc725670138d6f65ae2dbef241ac49a3.tar.xz
ARM: Fix subtle bug in LDM.
If the instruction faults mid-op the base register shouldn't be written back.
Diffstat (limited to 'src/arch/arm/insts')
-rw-r--r--src/arch/arm/insts/macromem.cc77
1 files changed, 50 insertions, 27 deletions
diff --git a/src/arch/arm/insts/macromem.cc b/src/arch/arm/insts/macromem.cc
index c03b7ccc1..8a82bd319 100644
--- a/src/arch/arm/insts/macromem.cc
+++ b/src/arch/arm/insts/macromem.cc
@@ -58,8 +58,13 @@ MacroMemOp::MacroMemOp(const char *mnem, ExtMachInst machInst,
{
uint32_t regs = reglist;
uint32_t ones = number_of_ones(reglist);
- // Remember that writeback adds a uop
- numMicroops = ones + (writeback ? 1 : 0) + 1;
+ // Remember that writeback adds a uop or two and the temp register adds one
+ numMicroops = ones + (writeback ? (load ? 2 : 1) : 0) + 1;
+
+ // It's technically legal to do a lot of nothing
+ if (!ones)
+ numMicroops = 1;
+
microOps = new StaticInstPtr[numMicroops];
uint32_t addr = 0;
@@ -70,28 +75,13 @@ MacroMemOp::MacroMemOp(const char *mnem, ExtMachInst machInst,
addr += 4;
StaticInstPtr *uop = microOps;
- StaticInstPtr wbUop;
- if (writeback) {
- if (up) {
- wbUop = new MicroAddiUop(machInst, rn, rn, ones * 4);
- } else {
- wbUop = new MicroSubiUop(machInst, rn, rn, ones * 4);
- }
- }
// Add 0 to Rn and stick it in ureg0.
// This is equivalent to a move.
*uop = new MicroAddiUop(machInst, INTREG_UREG0, rn, 0);
- // Write back at the start for loads. This covers the ldm exception return
- // case where the base needs to be written in the old mode. Stores may need
- // the original value of the base, but they don't change mode and can
- // write back at the end like before.
- if (load && writeback) {
- *++uop = wbUop;
- }
-
unsigned reg = 0;
+ unsigned regIdx = 0;
bool force_user = user & !bits(reglist, 15);
bool exception_ret = user & bits(reglist, 15);
@@ -101,19 +91,28 @@ MacroMemOp::MacroMemOp(const char *mnem, ExtMachInst machInst,
reg++;
replaceBits(regs, reg, 0);
- unsigned regIdx = reg;
+ regIdx = reg;
if (force_user) {
regIdx = intRegInMode(MODE_USER, regIdx);
}
if (load) {
- if (reg == INTREG_PC && exception_ret) {
- // This must be the exception return form of ldm.
- *++uop = new MicroLdrRetUop(machInst, regIdx,
- INTREG_UREG0, up, addr);
+ if (writeback && i == ones - 1) {
+ // If it's a writeback and this is the last register
+ // do the load into a temporary register which we'll move
+ // into the final one later
+ *++uop = new MicroLdrUop(machInst, INTREG_UREG1, INTREG_UREG0,
+ up, addr);
} else {
- *++uop = new MicroLdrUop(machInst, regIdx,
- INTREG_UREG0, up, addr);
+ // Otherwise just do it normally
+ if (reg == INTREG_PC && exception_ret) {
+ // This must be the exception return form of ldm.
+ *++uop = new MicroLdrRetUop(machInst, regIdx,
+ INTREG_UREG0, up, addr);
+ } else {
+ *++uop = new MicroLdrUop(machInst, regIdx,
+ INTREG_UREG0, up, addr);
+ }
}
} else {
*++uop = new MicroStrUop(machInst, regIdx, INTREG_UREG0, up, addr);
@@ -125,8 +124,32 @@ MacroMemOp::MacroMemOp(const char *mnem, ExtMachInst machInst,
addr -= 4;
}
- if (!load && writeback) {
- *++uop = wbUop;
+ if (writeback && ones) {
+ // put the register update after we're done all loading
+ if (up)
+ *++uop = new MicroAddiUop(machInst, rn, rn, ones * 4);
+ else
+ *++uop = new MicroSubiUop(machInst, rn, rn, ones * 4);
+
+ // If this was a load move the last temporary value into place
+ // this way we can't take an exception after we update the base
+ // register.
+ if (load && reg == INTREG_PC && exception_ret) {
+ *++uop = new MicroUopRegMovRet(machInst, 0, INTREG_UREG1);
+ warn("creating instruction with exception return at curTick:%d\n",
+ curTick());
+ } else if (load) {
+ *++uop = new MicroUopRegMov(machInst, regIdx, INTREG_UREG1);
+ if (reg == INTREG_PC) {
+ (*uop)->setFlag(StaticInstBase::IsControl);
+ (*uop)->setFlag(StaticInstBase::IsCondControl);
+ (*uop)->setFlag(StaticInstBase::IsIndirectControl);
+ // This is created as a RAS POP
+ if (rn == INTREG_SP)
+ (*uop)->setFlag(StaticInstBase::IsReturn);
+
+ }
+ }
}
(*uop)->setLastMicroop();