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Fix a bug with the ARM thumb2 CBNZ and CBNZ instructions that

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branch to the next instruction.  This can not be encoded but can be
turned into a NOP.

rdar://15062072


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@198904 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Kevin Enderby 2014-01-10 00:43:32 +00:00
parent 36c48cad0d
commit d9615670b7
2 changed files with 53 additions and 1 deletions
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21
lib/Target/ARM/MCTargetDesc/ARMAsmBackend.cpp
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@ -155,6 +155,8 @@ static unsigned getRelaxedOpcode(unsigned Op) {
case ARM::tLDRpci: return ARM::t2LDRpci;
case ARM::tADR: return ARM::t2ADR;
case ARM::tB: return ARM::t2B;
case ARM::tCBZ: return ARM::tHINT;
case ARM::tCBNZ: return ARM::tHINT;
}
}
@ -196,6 +198,12 @@ bool ARMAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
int64_t Offset = int64_t(Value) - 4;
return Offset > 1020 || Offset < 0 || Offset & 3;
}
case ARM::fixup_arm_thumb_cb:
// If we have a Thumb CBZ or CBNZ instruction and its target is the next
// instruction it is is actually out of range for the instruction.
// It will be changed to a NOP.
int64_t Offset = (Value & ~1);
return Offset == 2;
}
llvm_unreachable("Unexpected fixup kind in fixupNeedsRelaxation()!");
}
@ -212,7 +220,18 @@ void ARMAsmBackend::relaxInstruction(const MCInst &Inst, MCInst &Res) const {
report_fatal_error("unexpected instruction to relax: " + OS.str());
}
// The instructions we're relaxing have (so far) the same operands.
// If we are changing Thumb CBZ or CBNZ instruction to a NOP, aka tHINT, we
// have to change the operands too.
if ((Inst.getOpcode() == ARM::tCBZ || Inst.getOpcode() == ARM::tCBNZ) &&
RelaxedOp == ARM::tHINT) {
Res.setOpcode(RelaxedOp);
Res.addOperand(MCOperand::CreateImm(0));
Res.addOperand(MCOperand::CreateImm(14));
Res.addOperand(MCOperand::CreateReg(0));
return;
}
// The rest of instructions we're relaxing have the same operands.
// We just need to update to the proper opcode.
Res = Inst;
Res.setOpcode(RelaxedOp);

33
test/MC/ARM/thumb2-cbn-to-next-inst.s Normal file
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@ -0,0 +1,33 @@
@ RUN: llvm-mc -triple thumbv7-apple-darwin -filetype=obj -o %t.o %s
@ RUN: llvm-objdump -triple thumbv7-apple-darwin -d %t.o | FileCheck %s
.thumb
start:
.thumb_func start
add r1, r2, r3
cbnz r2, L1 @ this can't be encoded, must turn into a nop
L1:
add r4, r5, r6
cbnz r2, L2
sub r7, r8, r9
L2:
add r7, r8, r9
cbz r2, L3 @ this can't be encoded, must turn into a nop
L3:
add r10, r11, r12
cbz r2, L4
sub r7, r8, r9
L4:
add r3, r4, r5
@ CHECK: 0: 02 eb 03 01 add.w r1, r2, r3
@ CHECK: 4: 00 bf nop
@ CHECK: 6: 05 eb 06 04 add.w r4, r5, r6
@ CHECK: a: 0a b9 cbnz r2, #2
@ CHECK: c: a8 eb 09 07 sub.w r7, r8, r9
@ CHECK: 10: 08 eb 09 07 add.w r7, r8, r9
@ CHECK: 14: 00 bf nop
@ CHECK: 16: 0b eb 0c 0a add.w r10, r11, r12
@ CHECK: 1a: 0a b1 cbz r2, #2
@ CHECK: 1c: a8 eb 09 07 sub.w r7, r8, r9
@ CHECK: 20: 04 eb 05 03 add.w r3, r4, r5