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[lld][WebAssemlby] Always enable mutable-globals feature in PIC mode 

This works around an issue where the feature can be forgotten
in the case of LTO + object file with no functions.

See: https://bugs.llvm.org/show_bug.cgi?id=52339

Differential Revision: https://reviews.llvm.org/D112769
This commit is contained in:
Sam Clegg 2021-10-28 15:25:43 -07:00
parent 2321ac195c
commit 50bfc45109
2 changed files with 28 additions and 0 deletions
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21
lld/test/wasm/lto/pic-empty.s Normal file
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@ -0,0 +1,21 @@
; Test that LTO objects with no function can still be linked as shared
; libraries.
; We had a bug where the mutable-globals feature was not being added
; so the linker-generated import of `__stack_pointer` (which is currently
; mandatory for ; shared libraries) was generating a linker error.
; See https://bugs.llvm.org/show_bug.cgi?id=52339
; RUN: llvm-as %s -o %t.o
; RUN: wasm-ld -lto-O2 --experimental-pic -shared --no-gc-sections --export=tls_int %t.o -o %t.so
; RUN: obj2yaml %t.so | FileCheck %s
target datalayout = "e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-f128:64-n32:64-S128-ni:1:10:20"
target triple = "wasm32-unknown-emscripten"
@tls_int = dso_local thread_local global i32 99
; CHECK: - Type: CUSTOM
; CHECK: Name: target_features
; CHECK: Features:
; CHECK: - Prefix: USED
; CHECK: Name: mutable-globals

7
lld/wasm/Writer.cpp
View File

@ -433,6 +433,13 @@ void Writer::populateTargetFeatures() {
SmallSet<std::string, 8> &allowed = out.targetFeaturesSec->features;
bool tlsUsed = false;
if (config->isPic) {
// This should not be necessary because all PIC objects should
// contain the mutable-globals feature.
// TODO(https://bugs.llvm.org/show_bug.cgi?id=52339)
allowed.insert("mutable-globals");
}
// Only infer used features if user did not specify features
bool inferFeatures = !config->features.hasValue();