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[lld][WebAssembly] Fix crash on un-used __tls_base symbol

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In the case that TLS is used in the single-threaded program, and
therefore effectively lowered away, we still optionally create a
`__tls_base` symbols, but the code for setting it was assuming it was
always created.

Differential Revision: https://reviews.llvm.org/D109518
This commit is contained in:
Sam Clegg
2021-09-09 11:55:08 -04:00
parent c34f3780a7
commit 6355234660
3 changed files with 65 additions and 2 deletions
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63
lld/test/wasm/tls-non-shared-memory-basic.s Normal file
View File

@@ -0,0 +1,63 @@
# Simplified version of tls-non-shared-memory.s that does not reference
# __tls_base
# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
.section .tdata.tls1,"",@
.globl tls1
.p2align 2
tls1:
.int32 43
.size tls1, 2
.section .custom_section.target_features,"",@
.int8 2
.int8 43
.int8 7
.ascii "atomics"
.int8 43
.int8 11
.ascii "bulk-memory"
# RUN: wasm-ld --no-gc-sections --no-entry -o %t.wasm %t.o
# RUN: obj2yaml %t.wasm | FileCheck %s
# RUN: wasm-ld --experimental-pic -shared -o %t.so %t.o
# RUN: obj2yaml %t.so | FileCheck %s --check-prefix=PIC
# CHECK: - Type: DATA
# CHECK-NEXT: Segments:
# CHECK-NEXT: - SectionOffset: 7
# CHECK-NEXT: InitFlags: 0
# CHECK-NEXT: Offset:
# CHECK-NEXT: Opcode: I32_CONST
# CHECK-NEXT: Value: 1024
# CHECK-NEXT: Content: 2B000000
# CHECK-NEXT: - Type: CUSTOM
# CHECK-NOT: - Type: IMPORT
# In PIC mode we expect TLS data and non-TLS data to be merged into
# a single segment which is initialized via the __memory_base import
# PIC: - Type: IMPORT
# PIC-NEXT: Imports:
# PIC-NEXT: - Module: env
# PIC-NEXT: Field: memory
# PIC-NEXT: Kind: MEMORY
# PIC-NEXT: Memory:
# PIC-NEXT: Minimum: 0x1
# PIC-NEXT: - Module: env
# PIC-NEXT: Field: __memory_base
# PIC-NEXT: Kind: GLOBAL
# PIC-NEXT: GlobalType: I32
# PIC: - Type: DATA
# PIC-NEXT: Segments:
# PIC-NEXT: - SectionOffset: 6
# PIC-NEXT: InitFlags: 0
# PIC-NEXT: Offset:
# PIC-NEXT: Opcode: GLOBAL_GET
# PIC-NEXT: Index: 0
# PIC-NEXT: Content: 2B000000
# PIC-NEXT: - Type: CUSTOM

2
lld/wasm/Driver.cpp
View File

@@ -651,7 +651,7 @@ static void createSyntheticSymbols() {
WasmSym::stackPointer->markLive();
}
if (config->sharedMemory && !config->relocatable) {
if (config->sharedMemory) {
WasmSym::tlsBase = createGlobalVariable("__tls_base", true);
WasmSym::tlsSize = createGlobalVariable("__tls_size", false);
WasmSym::tlsAlign = createGlobalVariable("__tls_align", false);

2
lld/wasm/Writer.cpp
View File

@@ -278,7 +278,7 @@ void Writer::layoutMemory() {
auto *tlsAlign = cast<DefinedGlobal>(WasmSym::tlsAlign);
setGlobalPtr(tlsAlign, int64_t{1} << seg->alignment);
} else {
} else if (WasmSym::tlsBase) {
auto *tlsBase = cast<DefinedGlobal>(WasmSym::tlsBase);
setGlobalPtr(tlsBase, memoryPtr);
}