[PATCH] D47755: [RISCV] Insert R_RISCV_ALIGN relocation type and Nops for code alignment when linker relaxation enabled

Thu Jan 10 08:48:59 PST 2019

asb added a comment.

In D47755#1334053 <https://reviews.llvm.org/D47755#1334053>, @shiva0217 wrote:

> Hi Alex, I have added a constant pool test case at the end of align.s to verify the padding behavior for constant pool. Once D45961 <https://reviews.llvm.org/D45961> landing and changing the behavior, we should be able to aware. It seems that GCC will insert Nops for padding constant pool. Could you illustrate more about "use .align with a value to fill with"? I could test on GCC.

I meant that .align/.p2align in GNU as accept a padding value https://sourceware.org/binutils/docs/as/Align.html#Align. It seems that for RISC-V, it accepts and uses this padding value even when relaxation is enabled, but won't emit the R_RISCV_RELAX in that case (which I suppose makes sense, as the linker wouldn't respect the padding value). I'm not saying we should definitely replicate GNU as here - obviously performing alignment without generating R_RISCV_RELAX is quite liable to break things unexpectedly. But it might not be a bad starting point if it's easy to support. Either way, we should have tests that demonsrate how we handle those cases.

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https://reviews.llvm.org/D47755