13ca0c87ed
__heap_base was not aligned. In practice, it will often be aligned
simply because it follows the stack, but when the stack is placed at the
beginning (with the --stack-first option), the __heap_base might be
unaligned. It could even be byte-aligned.
At least wasi-libc appears to expect that __heap_base is aligned:
659ff41456/dlmalloc/src/malloc.c (L5224)
While WebAssembly itself does not appear to require any alignment for
memory accesses, it is sometimes required when sharing a pointer
externally. For example, WASI might expect alignment up to 8:
https://github.com/WebAssembly/WASI/blob/main/phases/snapshot/docs.md#-timestamp-u64
This issue got introduced with the addition of the --stack-first flag:
https://reviews.llvm.org/D46141
I suspect the lack of alignment wasn't intentional here.
Differential Revision: https://reviews.llvm.org/D106499
54 lines
2.4 KiB
Plaintext
54 lines
2.4 KiB
Plaintext
; Test that the --stack-first option places the stack at the start of linear
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; memory. In this case the --stack-first option is being passed along with a
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; stack size of 512. This means (since the stack grows down) the stack pointer
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; global should be initialized to 512.
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; Also test that __heap_base is still aligned with the --stack-first option.
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RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown %p/Inputs/stack-first.s -o %t.o
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RUN: wasm-ld -z stack-size=512 --stack-first --export=__data_end --export=__heap_base --export=someByte -o %t.wasm %t.o
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RUN: obj2yaml %t.wasm | FileCheck %s
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CHECK: - Type: GLOBAL
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CHECK-NEXT: Globals:
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CHECK-NEXT: - Index: 0
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CHECK-NEXT: Type: I32
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CHECK-NEXT: Mutable: true
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CHECK-NEXT: InitExpr:
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CHECK-NEXT: Opcode: I32_CONST
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CHECK-NEXT: Value: 512
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CHECK-NEXT: - Index: 1
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CHECK-NEXT: Type: I32
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CHECK-NEXT: Mutable: false
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CHECK-NEXT: InitExpr:
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CHECK-NEXT: Opcode: I32_CONST
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CHECK-NEXT: Value: 512
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CHECK-NEXT: - Index: 2
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CHECK-NEXT: Type: I32
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CHECK-NEXT: Mutable: false
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CHECK-NEXT: InitExpr:
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CHECK-NEXT: Opcode: I32_CONST
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CHECK-NEXT: Value: 513
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CHECK-NEXT: - Index: 3
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CHECK-NEXT: Type: I32
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CHECK-NEXT: Mutable: false
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CHECK-NEXT: InitExpr:
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CHECK-NEXT: Opcode: I32_CONST
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CHECK-NEXT: Value: 528
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CHECK-NEXT: - Type: EXPORT
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CHECK-NEXT: Exports:
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CHECK-NEXT: - Name: memory
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CHECK-NEXT: Kind: MEMORY
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CHECK-NEXT: Index: 0
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CHECK-NEXT: - Name: _start
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CHECK-NEXT: Kind: FUNCTION
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CHECK-NEXT: Index: 0
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CHECK-NEXT: - Name: someByte
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CHECK-NEXT: Kind: GLOBAL
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CHECK-NEXT: Index: 1
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CHECK-NEXT: - Name: __data_end
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CHECK-NEXT: Kind: GLOBAL
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CHECK-NEXT: Index: 2
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CHECK-NEXT: - Name: __heap_base
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CHECK-NEXT: Kind: GLOBAL
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CHECK-NEXT: Index: 3
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