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Fix a bug with the ARM thumb2 CBNZ and CBNZ instructions that
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
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@ -155,6 +155,8 @@ static unsigned getRelaxedOpcode(unsigned Op) {
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case ARM::tLDRpci: return ARM::t2LDRpci;
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case ARM::tLDRpci: return ARM::t2LDRpci;
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case ARM::tADR: return ARM::t2ADR;
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case ARM::tADR: return ARM::t2ADR;
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case ARM::tB: return ARM::t2B;
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case ARM::tB: return ARM::t2B;
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case ARM::tCBZ: return ARM::tHINT;
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case ARM::tCBNZ: return ARM::tHINT;
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}
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}
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}
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}
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@ -196,6 +198,12 @@ bool ARMAsmBackend::fixupNeedsRelaxation(const MCFixup &Fixup,
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int64_t Offset = int64_t(Value) - 4;
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int64_t Offset = int64_t(Value) - 4;
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return Offset > 1020 || Offset < 0 || Offset & 3;
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return Offset > 1020 || Offset < 0 || Offset & 3;
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}
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}
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case ARM::fixup_arm_thumb_cb:
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// If we have a Thumb CBZ or CBNZ instruction and its target is the next
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// instruction it is is actually out of range for the instruction.
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// It will be changed to a NOP.
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int64_t Offset = (Value & ~1);
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return Offset == 2;
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}
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}
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llvm_unreachable("Unexpected fixup kind in fixupNeedsRelaxation()!");
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llvm_unreachable("Unexpected fixup kind in fixupNeedsRelaxation()!");
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}
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}
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@ -212,7 +220,18 @@ void ARMAsmBackend::relaxInstruction(const MCInst &Inst, MCInst &Res) const {
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report_fatal_error("unexpected instruction to relax: " + OS.str());
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report_fatal_error("unexpected instruction to relax: " + OS.str());
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}
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}
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// The instructions we're relaxing have (so far) the same operands.
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// If we are changing Thumb CBZ or CBNZ instruction to a NOP, aka tHINT, we
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// have to change the operands too.
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if ((Inst.getOpcode() == ARM::tCBZ || Inst.getOpcode() == ARM::tCBNZ) &&
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RelaxedOp == ARM::tHINT) {
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Res.setOpcode(RelaxedOp);
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Res.addOperand(MCOperand::CreateImm(0));
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Res.addOperand(MCOperand::CreateImm(14));
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Res.addOperand(MCOperand::CreateReg(0));
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return;
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}
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// The rest of instructions we're relaxing have the same operands.
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// We just need to update to the proper opcode.
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// We just need to update to the proper opcode.
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Res = Inst;
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Res = Inst;
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Res.setOpcode(RelaxedOp);
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Res.setOpcode(RelaxedOp);
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33
test/MC/ARM/thumb2-cbn-to-next-inst.s
Normal file
33
test/MC/ARM/thumb2-cbn-to-next-inst.s
Normal file
@ -0,0 +1,33 @@
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@ RUN: llvm-mc -triple thumbv7-apple-darwin -filetype=obj -o %t.o %s
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@ RUN: llvm-objdump -triple thumbv7-apple-darwin -d %t.o | FileCheck %s
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.thumb
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start:
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.thumb_func start
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add r1, r2, r3
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cbnz r2, L1 @ this can't be encoded, must turn into a nop
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L1:
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add r4, r5, r6
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cbnz r2, L2
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sub r7, r8, r9
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L2:
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add r7, r8, r9
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cbz r2, L3 @ this can't be encoded, must turn into a nop
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L3:
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add r10, r11, r12
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cbz r2, L4
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sub r7, r8, r9
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L4:
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add r3, r4, r5
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@ CHECK: 0: 02 eb 03 01 add.w r1, r2, r3
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@ CHECK: 4: 00 bf nop
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@ CHECK: 6: 05 eb 06 04 add.w r4, r5, r6
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@ CHECK: a: 0a b9 cbnz r2, #2
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@ CHECK: c: a8 eb 09 07 sub.w r7, r8, r9
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@ CHECK: 10: 08 eb 09 07 add.w r7, r8, r9
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@ CHECK: 14: 00 bf nop
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@ CHECK: 16: 0b eb 0c 0a add.w r10, r11, r12
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@ CHECK: 1a: 0a b1 cbz r2, #2
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@ CHECK: 1c: a8 eb 09 07 sub.w r7, r8, r9
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@ CHECK: 20: 04 eb 05 03 add.w r3, r4, r5
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