[BOLT] Support computed goto and allow map addrs inside functions #120267

Rin18 · 2024-12-17T17:05:46Z

Create entry points for addresses referenced by dynamic relocations and allow getNewFunctionOrDataAddress to map addrs inside functions. By adding addresses referenced by dynamic relocations as entry points, this patch fixes an issue where bolt fails on code using computing goto's. This also fixes a mapping issue with the bugfix from this PR: #117766.

…ic relocations and allow getNewFunctionOrDataAddress to map addrs inside functions. By adding addresses referenced by dynamic relocations as entry points, this patch fixes an issue where bolt fails on code using computing goto's. This also fixes a mapping issue with the bugfix from this PR: llvm#117766.

llvmbot · 2024-12-17T17:06:35Z

@llvm/pr-subscribers-bolt

Author: Rin Dobrescu (Rin18)

Changes

By adding addresses referenced by dynamic relocations as entry points, this patch fixes an issue where bolt fails on code using computing goto's. This also fixes a mapping issue with the bugfix from this PR: #117766.

Full diff: https://github.com/llvm/llvm-project/pull/120267.diff

2 Files Affected:

(modified) bolt/lib/Rewrite/RewriteInstance.cpp (+9-1)
(added) bolt/test/AArch64/computed-goto.s (+39)

diff --git a/bolt/lib/Rewrite/RewriteInstance.cpp b/bolt/lib/Rewrite/RewriteInstance.cpp
index 4329235d470497..55fcd6b6e782c4 100644
--- a/bolt/lib/Rewrite/RewriteInstance.cpp
+++ b/bolt/lib/Rewrite/RewriteInstance.cpp
@@ -2439,6 +2439,14 @@ void RewriteInstance::readDynamicRelocations(const SectionRef &Section,
     if (Symbol)
       SymbolIndex[Symbol] = getRelocationSymbol(InputFile, Rel);
 
+    const uint64_t SymAddress = SymbolAddress + Addend;
+    BinaryFunction *Func = BC->getBinaryFunctionContainingAddress(SymAddress);
+    if(Func){
+      const uint64_t FunctionOffset = SymAddress - Func->getAddress();
+      if(FunctionOffset)
+        Func->addEntryPointAtOffset(FunctionOffset);
+    }
+
     BC->addDynamicRelocation(Rel.getOffset(), Symbol, RType, Addend);
   }
 }
@@ -5599,7 +5607,7 @@ uint64_t RewriteInstance::getNewFunctionOrDataAddress(uint64_t OldAddress) {
         for (const BinaryBasicBlock &BB : *BF)
           if (BB.isEntryPoint() &&
               (BF->getAddress() + BB.getOffset()) == OldAddress)
-            return BF->getOutputAddress() + BB.getOffset();
+            return BB.getOutputStartAddress();
       }
       BC->errs() << "BOLT-ERROR: unable to get new address corresponding to "
                     "input address 0x"
diff --git a/bolt/test/AArch64/computed-goto.s b/bolt/test/AArch64/computed-goto.s
new file mode 100644
index 00000000000000..043f9a8e37e6b0
--- /dev/null
+++ b/bolt/test/AArch64/computed-goto.s
@@ -0,0 +1,39 @@
+# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown %s -o %t.o
+# RUN: %clang %cflags %t.o -o %t.exe -Wl,-q
+# RUN: llvm-bolt %t.exe -o %t.bolt 2>&1 | FileCheck %s
+
+## Before bolt could handle mapping addresses within moved functions, it
+## would bail out with an error of the form:
+## BOLT-ERROR: unable to get new address corresponding to input address 0x10390 in function main. Consider adding this function to --skip-funcs=...
+## These addresses arise if computed GOTO is in use.
+## Check that bolt does not emit any error.
+
+# CHECK-NOT: BOLT-ERROR
+
+.globl  main
+.p2align        2
+.type   main,@function
+main:
+.cfi_startproc
+        adrp    x8, .L__const.main.ptrs+8
+        add     x8, x8, :lo12:.L__const.main.ptrs+8
+        ldr     x9, [x8], #8
+        br      x9
+
+.Label0: // Block address taken
+        ldr     x9, [x8], #8
+        br      x9
+
+.Label1: // Block address taken
+        mov     w0, #42
+        ret
+
+.Lfunc_end0:
+.size   main, .Lfunc_end0-main
+.cfi_endproc
+        .type   .L__const.main.ptrs,@object
+        .section        .data.rel.ro,"aw",@progbits
+        .p2align        3, 0x0
+.L__const.main.ptrs:
+        .xword  .Label0
+        .xword  .Label1

github-actions · 2024-12-17T17:10:08Z

✅ With the latest revision this PR passed the C/C++ code formatter.

aaupov

Looks good overall. The PR isn't limited to AArch64, so please drop that from the title. Please make the title more concise, e.g. "Support computed goto", expanding what is changed in the summary.

bolt/lib/Rewrite/RewriteInstance.cpp

bolt/test/AArch64/computed-goto.s

bolt/lib/Rewrite/RewriteInstance.cpp

Rin18 · 2024-12-18T11:25:27Z

Looks good overall. The PR isn't limited to AArch64, so please drop that from the title. Please make the title more concise, e.g. "Support computed goto", expanding what is changed in the summary.

Thanks for pointing this out, I'll change the title and summary.

ms178 · 2025-01-01T21:48:22Z

@Rin18 FYI, this patch might help to improve the usage of BOLT in Python as discussed in a related Python issue, see the comment and discussion in: python/cpython#124948 (comment)

Maybe it is a good test case for this MR, too.

Rin18 · 2025-01-02T13:47:04Z

@Rin18 FYI, this patch might help to improve the usage of BOLT in Python as discussed in a related Python issue, see the comment and discussion in: python/cpython#124948 (comment)

Maybe it is a good test case for this MR, too.

Thanks for bringing this to my attention, I'll need to look into the mentioned issue and see if this patch impacts it.

ms178 · 2025-01-02T15:47:58Z

Thanks for bringing this to my attention, I'll need to look into the mentioned issue and see if this patch impacts it.

Great, please also notice some downstream work on the python side which works around the current BOLT issues and might provide some hints: astral-sh/python-build-standalone#463

Ideally, there should be no need to use --skip-funcs=sre_ucs1_match/1,_PyEval_EvalFrameDefault.localalias/1

Rin18 · 2025-01-03T14:24:29Z

Thanks for bringing this to my attention, I'll need to look into the mentioned issue and see if this patch impacts it.

Great, please also notice some downstream work on the python side which works around the current BOLT issues and might provide some hints: astral-sh/python-build-standalone#463

Ideally, there should be no need to use --skip-funcs=sre_ucs1_match/1,_PyEval_EvalFrameDefault.localalias/1

I've taken a look at the link to the issue you've mentioned. This patch provides support for computed goto's. Once the PR is merged, it should get rid of the need to provide the --skip-funcs flag.

- Updated BOLT flags; unfortunately three functions still need to get skipped even with a patched LLVM with llvm/llvm-project#120267

Rin18 · 2025-01-20T16:40:05Z

I've added another test that is target independent. Is there anything else needed to approve this patch?

Rin18 · 2025-01-23T17:12:49Z

I've tested this patch on an aarch64 python3.12 build and found that it allows BOLT to run without --skip-funcs flags.
Without this patch the following error occurs:

llvm-bolt -o test.out.bolt python3.12
BOLT-ERROR: unable to get new address corresponding to input address 0x1b3f14 in function sre_ucs1_match/1. Consider adding this function to --skip-funcs=...

These functions no longer need to be skipped when goto patch is applied:

sre_ucs1_match/1; sre_ucs2_match/1; sre_ucs4_match/1; _PyEval_EvalFrameDefault.localalias/1

ilinpv · 2025-01-23T17:32:47Z

@aaupov @rafaelauler Does it make sense to add aarch64 python3.12 to https://github.com/rafaelauler/bolt-tests/tree/main/test/AArch64 tests without --skip-funcs when the patch merged?

zanieb · 2025-01-23T17:46:25Z

@Rin18 that's great to hear! Looking forward to using this downstream.

aaupov · 2025-01-23T18:27:36Z

@aaupov @rafaelauler Does it make sense to add aarch64 python3.12 to https://github.com/rafaelauler/bolt-tests/tree/main/test/AArch64 tests without --skip-funcs when the patch merged?

Yes, please make a PR there.

ms178 · 2025-01-23T19:25:44Z

I've tested this patch on an aarch64 python3.12 build and found that it allows BOLT to run without --skip-funcs flags. Without this patch the following error occurs:
llvm-bolt -o test.out.bolt python3.12
BOLT-ERROR: unable to get new address corresponding to input address 0x1b3f14 in function sre_ucs1_match/1. Consider adding this function to --skip-funcs=...
These functions no longer need to be skipped when goto patch is applied:
sre_ucs1_match/1; sre_ucs2_match/1; sre_ucs4_match/1; _PyEval_EvalFrameDefault.localalias/1

I can confirm that it works on Intel Raptor Lake as well. With this patch applied to e4f03b1, compiling python 3.13.1 with --enable-bolt does work now which previously did not.

Rin18 · 2025-01-28T16:41:22Z

I've also tested this patch on an aarch64 postgres build and found that it allows BOLT to run without --skip-funcs flags.
Without this patch the following error occurs:

llvm-bolt -o test.out.bolt postgres
BOLT-ERROR: unable to get new address corresponding to input address 0x2cb1b0 in function ExecInterpExpr/1(*2). Consider adding this function to --skip-funcs=...

The ExecInterpExpr/1 function no longer need to be skipped when goto patch is applied.

maksfb

Thank you for the PR!

maksfb · 2025-01-28T21:51:34Z

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -5599,7 +5606,7 @@ uint64_t RewriteInstance::getNewFunctionOrDataAddress(uint64_t OldAddress) {
        for (const BinaryBasicBlock &BB : *BF)


Not directly related to your change, but we should use BinaryFunction::forEachEntryPoint() here.

maksfb · 2025-01-28T21:54:25Z

bolt/lib/Rewrite/RewriteInstance.cpp

+    if (Func && !Func->isInConstantIsland(SymAddress)) {
+      if (const uint64_t SymOffset = SymAddress - Func->getAddress())
+        Func->addEntryPointAtOffset(SymOffset);
+    }


Can we add more checks? E.g., what happens if Symbol points to a function and SymAddress falls into another function? What if the reference is in the constant island? It's better to fail at build time.

I'll look into adding more checks.

bolt/test/AArch64/computed-goto.s

bolt/test/dynamic-relocs.test

aaupov

Looks good to me, thank you for working on this.
Please address the feedback from Maksim.

small nit: please drop trailing dot in the title

bolt/test/dynamic-relocs.test

Rin18 requested review from aaupov, maksfb, rafaelauler, ayermolo and dcci as code owners December 17, 2024 17:05

llvmbot added the BOLT label Dec 17, 2024

Rin18 requested a review from peterwaller-arm December 17, 2024 17:06

aaupov reviewed Dec 17, 2024

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peterwaller-arm mentioned this pull request Dec 18, 2024

[BOLT] Allow getNewFunctionOrDataAddress to map addrs inside functions #117766

Closed

yota9 reviewed Dec 18, 2024

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Rin18 changed the title ~~[BOLT][AArch64] Create entry points for addresses referenced by dynamic relocations and allow getNewFunctionOrDataAddress to map addrs inside functions.~~ [BOLT] Support computed goto and allow map addrs inside functions. Dec 18, 2024

rin-arm added 2 commits December 18, 2024 12:11

Fix clang-format and address PR comments.

dd67da5

Remove redundant test and expand different test.

1dd6d5a

ms178 mentioned this pull request Dec 31, 2024

[BOLT] [3.12] Python 3.12.7 --enable bolt option not working python/cpython#124948

Open

ms178 mentioned this pull request Jan 2, 2025

[BOLT] llvm-bolt crashes during Python 3.13.1 build with addDebugFilenameToUnit segmentation fault #121213

Open

zanieb mentioned this pull request Jan 4, 2025

BOLT fails with --enabled-shared on LLVM 19 with "unable to get new address" python/cpython#128472

Closed

ilinpv mentioned this pull request Jan 10, 2025

[BOLT] Enable hugify for AArch64 #117158

Open

ms178 added a commit to ms178/archpkgbuilds that referenced this pull request Jan 10, 2025

Update bolt.patch

e14ef21

- Updated BOLT flags; unfortunately three functions still need to get skipped even with a patched LLVM with llvm/llvm-project#120267

Add target independent test.

b1d8033

ilinpv mentioned this pull request Jan 21, 2025

[BOLT][AArch64] unsupported CFI opcode on Ubuntu 24.04 and AL2023 #120992

Open

aaupov mentioned this pull request Jan 22, 2025

BOLT optimizations fail on Linux aarch64 python/cpython#128884

Open

Fix formatting issue.

b44c28a

maksfb reviewed Jan 28, 2025

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aaupov reviewed Jan 29, 2025

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bolt/test/dynamic-relocs.test Outdated Show resolved Hide resolved

Address comments regarding tests

39d46f3

Rin18 changed the title ~~[BOLT] Support computed goto and allow map addrs inside functions.~~ [BOLT] Support computed goto and allow map addrs inside functions Jan 31, 2025

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		@@ -5599,7 +5606,7 @@ uint64_t RewriteInstance::getNewFunctionOrDataAddress(uint64_t OldAddress) {
		for (const BinaryBasicBlock &BB : *BF)

[BOLT] Support computed goto and allow map addrs inside functions #120267

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[BOLT] Support computed goto and allow map addrs inside functions #120267

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