cgen: fix x86 segment-override memory operands in basic inline asm#27782
cgen: fix x86 segment-override memory operands in basic inline asm#27782fleximus wants to merge 1 commit into
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| if !stmt.is_basic { | ||
| g.write('%') // escape percent with percent in extended assembly | ||
| } | ||
| g.write('%${arg.segment}:') |
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In asm goto blocks that only provide the label list (for example asm goto amd64 { jmp gs:[16]; ; ; ; done }), the parser still leaves stmt.is_basic true because it only counts outputs/inputs/clobbers, but asm_stmt emits __asm__ goto (... : : : : label), which is extended asm. This branch therefore writes %gs: instead of %%gs:, and GCC/Clang parse %g as an operand escape (operand number missing after %-letter). Please base this escaping on whether the emitted C asm is extended, including stmt.is_goto, rather than is_basic alone.
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Fixes #27777
In basic inline assembly (no operand lists), the template string is passed to the assembler verbatim, so segment overrides like
gs:[16]were emitted as%%gs:16and rejected withinvalid register name. Registers already handled this viastmt.is_basic; this applies the same escaping rule to segment prefixes: single%in basic asm,%%in extended asm.Verified with the issue's repro (
v -freestanding -cc clang -keepc .) — the binary now disassembles tomov %rdi,%gs:0x10. Added a coutput testdata pair covering both the basic and extended forms.