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opt: Stop creating TargetMachine to infer the datalayout #169585

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Merged
merged 2 commits into from
Nov 26, 2025
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opt: Stop creating TargetMachine to infer the datalayout #169585

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4264dc6
opt: Stop creating TargetMachine to infer the datalayout
arsenm Nov 26, 2025
70af3bf
Reword error message
arsenm Nov 26, 2025
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4 changes: 2 additions & 2 deletions llvm/test/tools/opt/invalid-target.ll
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Expand Up @@ -7,10 +7,10 @@

;; Using "unknown" as the architecture is explicitly allowed (but warns)
; RUN: opt -mtriple=unknown -S -passes=no-op-module -o /dev/null < %s 2>&1 | FileCheck %s --check-prefix=UNKNOWN
; UNKNOWN: warning: failed to infer data layout: unable to get target for 'unknown', see --version and --triple.
; UNKNOWN: warning: failed to infer data layout from target triple{{$}}

;; However, any other invalid target triple should cause the tool to fail:
; RUN: not opt -mtriple=invalid -S -passes=no-op-module -o /dev/null < %s 2>&1 | FileCheck %s --check-prefix=INVALID
; INVALID: warning: failed to infer data layout: unable to get target for 'invalid', see --version and --triple.
; INVALID: warning: failed to infer data layout from target triple{{$}}
; INVALID-NEXT: unrecognized architecture 'invalid' provided.
; INVALID-EMPTY:
15 changes: 8 additions & 7 deletions llvm/tools/opt/optdriver.cpp
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Expand Up @@ -538,15 +538,16 @@ optMain(int argc, char **argv,
// the IR, we should default to an empty (default) DataLayout.
if (TripleStr.empty())
return std::nullopt;
// Otherwise we infer the DataLayout from the target machine.
Expected<std::unique_ptr<TargetMachine>> ExpectedTM =
codegen::createTargetMachineForTriple(TripleStr, GetCodeGenOptLevel());
if (!ExpectedTM) {
errs() << argv[0] << ": warning: failed to infer data layout: "
<< toString(ExpectedTM.takeError()) << "\n";

Triple TT(TripleStr);

std::string Str = TT.computeDataLayout();
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@arichardson arichardson Nov 26, 2025 •
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Can we also pass the value of the --target-abi= command line option here? Since depending on the ABI, there could be a different data layouts.
For testing this we could instantiate opt with e.g. MIPS n32 ABI or one of the ARM ABI variants that affect the data layout string.

I know this is a functional change rather than NFC, so also fine to defer until later.

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@arsenm arsenm Nov 26, 2025

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There's also apparently a target-abi module flag, and this doesn't seem like it's all handled correctly

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@arichardson arichardson Nov 26, 2025

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Yeah it seems to be mostly ignored which causes a bunch of issues with LTO (especially on RISC-V) such as #50591 / #69780. Probably easiest to ignore that attribute for now and only look at command line flags.

if (Str.empty()) {
errs() << argv[0]
<< ": warning: failed to infer data layout from target triple\n";
return std::nullopt;
}
return (*ExpectedTM)->createDataLayout().getStringRepresentation();
return Str;
};
std::unique_ptr<Module> M;
if (NoUpgradeDebugInfo)
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