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[NativeAOT] Inline TLS access for linux/arm64 #97910

Merged
merged 24 commits into from
Feb 15, 2024
Merged

[NativeAOT] Inline TLS access for linux/arm64 #97910

merged 24 commits into from
Feb 15, 2024

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kunalspathak
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@kunalspathak kunalspathak commented Feb 3, 2024 •
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We now generate the inlined TLS access during compilation

:	90000000 	adrp	x0, 0 <System_Console_System_ConsoleKeyInfo____GetFieldHelper>
			5a2f0: R_AARCH64_TLSDESC_ADR_PAGE21	tls_InlinedThreadStatics
   5a2f4:	91000000 	add	x0, x0, #0x0
			5a2f4: R_AARCH64_TLSDESC_ADD_LO12	tls_InlinedThreadStatics
   5a2f8:	d53bd041 	mrs	x1, tpidr_el0
   5a2fc:	f9400002 	ldr	x2, [x0]
			5a2fc: R_AARCH64_TLSDESC_LD64_LO12	tls_InlinedThreadStatics
   5a300:	d63f0040 	blr	x2
			5a300: R_AARCH64_TLSDESC_CALL	tls_InlinedThreadStatics
   5a304:	8b000020 	add	x0, x1, x0
   5a308:	f9400013 	ldr	x19, [x0]

which gets converted by the linker in following:

image

TODO

  • Sharedlibrary scenario fails for some reason. The objdump on the object file looks identical between before and after, however when I do objdump on the shared library i.e. .so file, I see a difference in bits for adrp which tells me that I am missing some relocation update, but cannot find out what. @MichalStrehovsky - any idea?
image
  • superpmi changes
  • Add IMAGE_REL_ARM64_TLSDESC* in ntimage.h?

@ghost ghost assigned kunalspathak Feb 3, 2024
@dotnet-issue-labeler dotnet-issue-labeler bot added the area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI label Feb 3, 2024
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Issue Details

We now generate the inlined TLS access during compilation

:	90000000 	adrp	x0, 0 <System_Console_System_ConsoleKeyInfo____GetFieldHelper>
			5a2f0: R_AARCH64_TLSDESC_ADR_PAGE21	tls_InlinedThreadStatics
   5a2f4:	91000000 	add	x0, x0, #0x0
			5a2f4: R_AARCH64_TLSDESC_ADD_LO12	tls_InlinedThreadStatics
   5a2f8:	d53bd041 	mrs	x1, tpidr_el0
   5a2fc:	f9400002 	ldr	x2, [x0]
			5a2fc: R_AARCH64_TLSDESC_LD64_LO12	tls_InlinedThreadStatics
   5a300:	d63f0040 	blr	x2
			5a300: R_AARCH64_TLSDESC_CALL	tls_InlinedThreadStatics
   5a304:	8b000020 	add	x0, x1, x0
   5a308:	f9400013 	ldr	x19, [x0]

which gets converted by the linker in following:

image

TODO

Sharedlibrary scenario fails for some reason. The objdump on the object file looks identical between before and after, however when I do objdump on the shared library i.e. .so file, I see a difference in bits for adrp which tells me that I am missing some relocation update, but cannot find out what.

image
Author: kunalspathak
Assignees: kunalspathak
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area-CodeGen-coreclr
Milestone: -

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@jkotas

@filipnavara
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  • The objdump on the object file looks identical between before and after, however when I do objdump on the shared library i.e. .so file, I see a difference in bits for adrp which tells me that I am missing some relocation update, but cannot find out what.

Can you dump the object file relocations for a given offset with readelf and share it?

@build-analysis build-analysis bot mentioned this pull request Feb 3, 2024
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Can you dump the object file relocations for a given offset with readelf and share it?

Here are the files. Look for ReturnsPrimitiveInt that is my test code.

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@filipnavara - did you get a chance to check this?
CC: @MichalStrehovsky and @VSadov - in case they see what is missing.

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did you get a chance to check this?

Sorry, I was out for the weekend and now I have an emergency to attend to... will hopefully get to look at it in the evening.

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filipnavara commented Feb 5, 2024 •
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I tried to reproduced it locally but all the tests passed.

Nevermind, I accidentally built a Debug build. Trying again.

@MichalStrehovsky
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I see a difference in bits for adrp which tells me that I am missing some relocation update, but cannot find out what. @MichalStrehovsky - any idea?

Are we generating the exact instruction sequence clang/gcc would generate? Various breadcrumbs online seem to suggest linkers want to see exact instruction sequences: https://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20150302/263562.html

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Are we generating the exact instruction sequence clang/gcc would generate?

It works for executable, so yes, we generate exact sequence. It is failing only from sharedlibrary. When @VSadov added initial support of hand assembly, he didn't add anything special for sharedlibrary, so not sure what is wrong.

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I can reproduce it locally. It helped to check out the correct branch 😅

Notably, the sequence is different from what clang generates.

clang:

 adrp	x0, 0 <foo>
    R_AARCH64_TLSDESC_ADR_PAGE21 foo
 ldr	x1, [x0]
    R_AARCH64_TLSDESC_LD64_LO12 foo
 add	x0, x0, #0x0
    R_AARCH64_TLSDESC_ADD_LO12 foo
 blr	x1
    R_AARCH64_TLSDESC_CALL foo
 mrs	x8, tpidr_el0
 ldr	w0, [x8, x0]

The ldr follows the page address before applying the add.

Shared libraries get a different rewrite than executables due to the way they are relocated at runtime.

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The ldr follows the page address before applying the add.

Ah, that could be it. I thought adrp/add is a pair and shouldn't matter. Let me fix it and see.

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The ldr follows the page address before applying the add.

Ah, that could be it. I thought adrp/add is a pair and shouldn't matter. Let me fix it and see.

This fixed the problem for sharedlibrary.

image

executable:

  G_M48060_IG03:  ;; offset=0x0020
              mrs     x1, tpidr_el0
              adrp    x0, [HIGH RELOC #0x4201B8]
              ldr     x2, [x0]
              add     x0, x0, [LOW RELOC #0x4201B8]
              blr     x0
              add     x0, x1, x0
              ldr     x19, [x0]
              cbz     x19, G_M48060_IG07
                                                ;; size=32 bbWeight=1 PerfScore 10.50
image

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/azp run runtime-nativeaot-outerloop

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superpmi changes:

I don't think we need any superpmi changes just for the relocs. I locally tried to collect and replay and it works fine

image

@kunalspathak kunalspathak marked this pull request as ready for review February 8, 2024 17:14
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@dotnet/jit-contrib

AndyAyersMS
AndyAyersMS approved these changes Feb 12, 2024
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src/coreclr/jit/lsraarmarch.cpp
// that we will attach to this node to guarantee that they are available
// during generating this node.
assert(call->gtFlags & GTF_TLS_GET_ADDR);
newRefPosition(REG_R0, currentLoc, RefTypeFixedReg, nullptr, genRegMask(REG_R0));
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Do these have to be R0/R1/R2 for the linker, or is this just a choice you've made to make things simpler?

Or is it the case that since the ultimate expansion has a call these choices don't add new constraints?

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They are used by the linker to match the pattern as seen here and thats how we did that in hand-assembly code here.

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@VSadov PTAL

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VSadov approved these changes Feb 15, 2024
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LGTM! Thanks!!

@kunalspathak kunalspathak merged commit dc7f703 into dotnet:main Feb 15, 2024
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@kunalspathak kunalspathak deleted the nativeaot-tls-linux-arm64 branch February 15, 2024 21:03
@kunalspathak kunalspathak mentioned this pull request Feb 15, 2024
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@VSadov VSadov VSadov approved these changes

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@BruceForstall BruceForstall BruceForstall approved these changes

@MichalStrehovsky MichalStrehovsky Awaiting requested review from MichalStrehovsky MichalStrehovsky is a code owner

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