[AArch64] Correctly disassemble TSB instruction #156362
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This was referenced Sep 1, 2025
This was referenced Sep 1, 2025
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@llvm/pr-subscribers-backend-aarch64 Author: Sergei Barannikov (s-barannikov) ChangesTSB instruction has one operand, but the generated disassembler is unable to decode it since the operand is not encoded into the instruction. AArch64InstPrinter has a special case for this instruction. With the changes proposed by #156358, the operand can now be decoded automatically and the workaround is no longer required. Full diff: https://github.com/llvm/llvm-project/pull/156362.diff 3 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AArch64SystemOperands.td b/llvm/lib/Target/AArch64/AArch64SystemOperands.td
index 1b0e90b0e0dc3..65b752ed40c90 100644
--- a/llvm/lib/Target/AArch64/AArch64SystemOperands.td
+++ b/llvm/lib/Target/AArch64/AArch64SystemOperands.td
@@ -362,7 +362,7 @@ def lookupTSBByName : SearchIndex {
let Key = ["Name"];
}
-def : TSB<"csync", 0>;
+def : TSB<"csync", 2>;
//===----------------------------------------------------------------------===//
// PRFM (prefetch) instruction options.
diff --git a/llvm/lib/Target/AArch64/CMakeLists.txt b/llvm/lib/Target/AArch64/CMakeLists.txt
index 833ce48ea1d7a..79b56ea9cf850 100644
--- a/llvm/lib/Target/AArch64/CMakeLists.txt
+++ b/llvm/lib/Target/AArch64/CMakeLists.txt
@@ -8,8 +8,7 @@ tablegen(LLVM AArch64GenAsmWriter1.inc -gen-asm-writer -asmwriternum=1)
tablegen(LLVM AArch64GenCallingConv.inc -gen-callingconv)
tablegen(LLVM AArch64GenDAGISel.inc -gen-dag-isel)
tablegen(LLVM AArch64GenDisassemblerTables.inc -gen-disassembler
- -ignore-non-decodable-operands
- -ignore-fully-defined-operands)
+ -ignore-non-decodable-operands)
tablegen(LLVM AArch64GenFastISel.inc -gen-fast-isel)
tablegen(LLVM AArch64GenGlobalISel.inc -gen-global-isel)
tablegen(LLVM AArch64GenO0PreLegalizeGICombiner.inc -gen-global-isel-combiner
diff --git a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
index 54b58e948daf2..2552ee3009338 100644
--- a/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
+++ b/llvm/lib/Target/AArch64/MCTargetDesc/AArch64InstPrinter.cpp
@@ -365,13 +365,6 @@ void AArch64InstPrinter::printInst(const MCInst *MI, uint64_t Address,
return;
}
- // Instruction TSB is specified as a one operand instruction, but 'csync' is
- // not encoded, so for printing it is treated as a special case here:
- if (Opcode == AArch64::TSB) {
- O << "\ttsb\tcsync";
- return;
- }
-
if (!PrintAliases || !printAliasInstr(MI, Address, STI, O))
printInstruction(MI, Address, STI, O);
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September 4, 2025 16:04
TSB instruction has one operand, but the generated disassembler didn't decode this operand. AArch64InstPrinter had a workaround for this. This instruction can now be disassembled correctly.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/163/builds/25981 Here is the relevant piece of the build log for the reference |
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TSB instruction has one operand, but the generated disassembler is unable to decode it since the operand is not encoded into the instruction. AArch64InstPrinter has a special case for this -- if the instruction being printed is TSB, it prints the only possible operand value, regardless of whether the operand is present or not.
With the changes proposed by #156358, the operand can now be decoded automatically and the workaround is no longer required.