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rust/compiler/rustc_target
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Matthias Krüger 12c102ec53
Rollup merge of #119431 - taiki-e:asm-s390x-reg-addr, r=Amanieu 
Support reg_addr register class in s390x inline assembly

In s390x, `r0` cannot be used as an address register (it is evaluated as zero in an address context).

Therefore, currently, in assemblies involving memory accesses, `r0` must be [marked as clobbered](1a1155653a/src/arch/s390x.rs (L58)) or [explicitly used to a non-address](1a1155653a/src/arch/s390x.rs (L135)) or explicitly use an address register to prevent `r0` from being allocated to a register for the address.

This patch adds a register class for allocating general-purpose registers, except `r0`, to make it easier to use address registers. (powerpc already has a register class (reg_nonzero) for a similar purpose.)

This is identical to the `a` constraint in LLVM and GCC:

https://llvm.org/docs/LangRef.html#supported-constraint-code-list
> a: A 32, 64, or 128-bit integer address register (excludes R0, which in an address context evaluates as zero).

https://gcc.gnu.org/onlinedocs/gcc/Machine-Constraints.html
> a
> Address register (general purpose register except r0)

cc ``@uweigand``

r? ``@Amanieu``
2024-01-04 15:33:59 +01:00
..
src Rollup merge of #119431 - taiki-e:asm-s390x-reg-addr, r=Amanieu 2024-01-04 15:33:59 +01:00
Cargo.toml Update to bitflags 2 in the compiler 2023-12-30 18:17:28 +01:00
README.md Fix outdated crate names in compiler docs 2021-04-08 11:12:14 -05:00

README.md

rustc_target contains some very low-level details that are specific to different compilation targets and so forth.

For more information about how rustc works, see the rustc dev guide.