[all-commits] [llvm/llvm-project] 2f91e9: [RISCV] Mark symbols used in inline asm for reloca...

[Anton Sidorenko via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2f91e98120f168b7ded6cb34d546dba178515cc4
      https://github.com/llvm/llvm-project/commit/2f91e98120f168b7ded6cb34d546dba178515cc4
  Author: Anton Sidorenko <anton.sidorenko at syntacore.com>
  Date:   2024-08-26 (Mon, 26 Aug 2024)

  Changed paths:
    M llvm/lib/Target/RISCV/RISCVAsmPrinter.cpp
    M llvm/test/CodeGen/RISCV/inline-asm-mem-constraint.ll

  Log Message:
  -----------
  [RISCV] Mark symbols used in inline asm for relocations as referenced (#104925)

Commit 5cd8d53cac00f taught RISCVMergeBaseOffset to handle inline asm,
however
there is at least one case uncovered for integrated as.

In the example below compiler generates pcrel relocation
(mcmodel=medany)
```
    volatile double double_val = 1.0;
    void foo() {
        asm volatile("fld f0, %0 \n\t" : : "m"(double_val) : "memory");
    }
```

And fails with the folliwng error
```
    error: could not find corresponding %pcrel_hi
          |       "fld f0, %0 \n\t"
    <inline asm>:1:2: note: instantiated into assembly here
          |         fld f0, %pcrel_lo(.Lpcrel_hi0)(a0)
```

After transformations MachineFunction contains inline asm instructions
with
'.Lpcrel_hi0' symbol that is not defined in inline asm, but referenced.
```
   ... = AUIPC ...(riscv-pcrel-hi) @double_val, pre-instr-symbol <mcsymbol .Lpcrel_hi0>
   INLINEASM &"fld f0, $0 \0A\09" ... target-flags(riscv-pcrel-lo) <mcsymbol .Lpcrel_hi0>
```

So, when AsmParser processes 'fld', it has to create a new symbol as
'.Lpcrel_hi0' already exists but not known to be referenced in inline
asm.
AsmParser avoids conflicts by renaming referenced by 'fld' symbol with
'.Lpcrel_hi00' name which does not exist. Resulting erroneous asm
```
    .Lpcrel_hi0:
        auipc   a0, %pcrel_hi(double_val)
        #APP
        fld     ft0, %pcrel_lo(.Lpcrel_hi00)(a0)
```

This change adds symbols used in memory operands to the list of
referenced ones.

Godbolt link: https://godbolt.org/z/aqrrsWKoK -- on the left you can
find incorrect labels for the integrated-as and on the right an error
when compiling to the binary object.



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