[WebAssembly] i32.const operands should be signed

[tlively]

Summary

This was causing large addresses to be emitted as negative numbers,
which rightfully caused crashes in binaryen.

[aheejin]

lld/test/wasm/data-segments.ll

91

It'd be better if we can get disassembly, but it seems to be not fully working yet

lld/wasm/Writer.cpp

661

Isn't [[ https://github.com/llvm/llvm-project/blob/c46d78d1b7a06aad11f8810279271224fc8466af/lld/wasm/OutputSegment.h#L39 | OutputSegment::startVA ]] already a uint32_t?

[sbc100]

lld/test/wasm/data-segments.ll

44

How does this change test the logic change? Seems like 10000 isn't large enough to trigger the binaryen crash?

[tlively]

lld/test/wasm/data-segments.ll

44

1000 encoded as unsigned leb in hex is 904E, bu as a signed leb it is 90CE00. The need to leave room for a sign bit bumps the encoding up to use the next byte.

91

+1

lld/wasm/Writer.cpp

661

Good catch, this was left over from some previous experimentation.

lld/test/wasm/data-segments.ll

 ; atomics, bulk memory, passive segments  => passive segments
 ; RUN: wasm-ld -no-gc-sections --no-entry --shared-memory --max-memory=131072 --passive-segments %t.atomics.bulk-mem.o -o %t.atomics.bulk-mem.passive.wasm
 ; RUN: obj2yaml %t.atomics.bulk-mem.passive.wasm | FileCheck %s --check-prefix PASSIVE
 
 target triple = "wasm32-unknown-unknown"
 
 @a = hidden global [6 x i8] c"hello\00", align 1
 @b = hidden global [8 x i8] c"goodbye\00", align 1
-@c = hidden global [9 x i8] c"whatever\00", align 1
+@c = hidden global [10000 x i8] zeroinitializer, align 1
 @d = hidden global i32 42, align 4
 
 @e = private constant [9 x i8] c"constant\00", align 1
 @f = private constant i8 43, align 4
 
 ; ERROR: 'bulk-memory' feature must be used in order to emit passive segments
 
 ; ACTIVE-LABEL: - Type:            CODE
 ; ACTIVE-NEXT:    Functions:
 ; ACTIVE-NEXT:      - Index:           0
 ; ACTIVE-NEXT:        Locals:          []
 ; ACTIVE-NEXT:        Body:            0B
 ; ACTIVE-NEXT:  - Type:            DATA
 ; ACTIVE-NEXT:    Segments:
 ; ACTIVE-NEXT:      - SectionOffset:   7
 ; ACTIVE-NEXT:        InitFlags:       0
 ; ACTIVE-NEXT:        Offset:
-; ACTIVE-NEXT:        Opcode:          I32_CONST
-; ACTIVE-NEXT:        Value:           1024
-; ACTIVE-NEXT:        Content:         68656C6C6F00676F6F6462796500776861746576657200002A000000
-; ACTIVE-NEXT:      - SectionOffset:   41
+; ACTIVE-NEXT:          Opcode:          I32_CONST
+; ACTIVE-NEXT:          Value:           1024
+; ACTIVE-NEXT:        Content:         68656C6C6F00676F6F646279650000002A000000
+; ACTIVE-NEXT:      - SectionOffset:   34
 ; ACTIVE-NEXT:        InitFlags:       0
 ; ACTIVE-NEXT:        Offset:
-; ACTIVE-NEXT:        Opcode:          I32_CONST
-; ACTIVE-NEXT:        Value:           1052
+; ACTIVE-NEXT:          Opcode:          I32_CONST
+; ACTIVE-NEXT:          Value:           1044
+; ACTIVE-NEXT:        Content:         '0000000000
+; ACTIVE-SAME:                           0000000000'
+; ACTIVE-NEXT:      - SectionOffset:   10041
+; ACTIVE-NEXT:        InitFlags:       0
+; ACTIVE-NEXT:        Offset:
+; ACTIVE-NEXT:          Opcode:          I32_CONST
+; ACTIVE-NEXT:          Value:           11044
 ; ACTIVE-NEXT:        Content:         636F6E7374616E74000000002B
 ; ACTIVE-NEXT:  - Type:            CUSTOM
 ; ACTIVE-NEXT:    Name:            name
 ; ACTIVE-NEXT:    FunctionNames:
 ; ACTIVE-NEXT:      - Index:           0
 ; ACTIVE-NEXT:        Name:            __wasm_call_ctors
 
 ; PASSIVE-LABEL: - Type:            CODE
 ; PASSIVE-NEXT:    Functions:
 ; PASSIVE-NEXT:      - Index:           0
 ; PASSIVE-NEXT:        Locals:          []
 ; PASSIVE-NEXT:        Body:            10010B
 ; PASSIVE-NEXT:      - Index:           1
 ; PASSIVE-NEXT:        Locals:          []
-; PASSIVE-NEXT:        Body:            4180084100411CFC080000FC0900419C084100410DFC080100FC09010B
+; PASSIVE-NEXT:        Body:            41800841004114FC080000FC090041940841004190CE00FC080100FC090141A4D6004100410DFC080200FC09020B
 ; PASSIVE-NEXT:  - Type:            DATA
 ; PASSIVE-NEXT:    Segments:
 ; PASSIVE-NEXT:      - SectionOffset:   3
 ; PASSIVE-NEXT:        InitFlags:       1
-; PASSIVE-NEXT:        Content:         68656C6C6F00676F6F6462796500776861746576657200002A000000
-; PASSIVE-NEXT:      - SectionOffset:   33
+; PASSIVE-NEXT:        Content:         68656C6C6F00676F6F646279650000002A000000
+; PASSIVE-NEXT:      - SectionOffset:   26
+; PASSIVE-NEXT:        InitFlags:       1
+; PASSIVE-NEXT:        Content:         '0000000000
+; PASSIVE-SAME:                           0000000000'
+; PASSIVE-NEXT:      - SectionOffset:   10028
 ; PASSIVE-NEXT:        InitFlags:       1
 ; PASSIVE-NEXT:        Content:         636F6E7374616E74000000002B
 ; PASSIVE-NEXT:  - Type:            CUSTOM
 ; PASSIVE-NEXT:    Name:            name
 ; PASSIVE-NEXT:    FunctionNames:
 ; PASSIVE-NEXT:      - Index:           0
 ; PASSIVE-NEXT:        Name:            __wasm_call_ctors
 ; PASSIVE-NEXT:      - Index:           1
 ; PASSIVE-NEXT:        Name:            __wasm_init_memory

lld/wasm/Writer.cpp

std::string bodyContent;
     raw_string_ostream os(bodyContent);
     writeUleb128(os, 0, "num locals");
 
     // initialize passive data segments
     for (const OutputSegment *s : segments) {
       if (s->initFlags & WASM_SEGMENT_IS_PASSIVE) {
         // destination address
         writeU8(os, WASM_OPCODE_I32_CONST, "i32.const");
-        writeUleb128(os, s->startVA, "destination address");
+        writeSleb128(os, uint32_t(s->startVA), "destination address");
         // source segment offset
         writeU8(os, WASM_OPCODE_I32_CONST, "i32.const");
-        writeUleb128(os, 0, "segment offset");
+        writeSleb128(os, 0, "segment offset");
         // memory region size
         writeU8(os, WASM_OPCODE_I32_CONST, "i32.const");
-        writeUleb128(os, s->size, "memory region size");
+        writeSleb128(os, s->size, "memory region size");
         // memory.init instruction
         writeU8(os, WASM_OPCODE_MISC_PREFIX, "bulk-memory prefix");
         writeUleb128(os, WASM_OPCODE_MEMORY_INIT, "MEMORY.INIT");
         writeUleb128(os, s->index, "segment index immediate");
         writeU8(os, 0, "memory index immediate");
         // data.drop instruction
         writeU8(os, WASM_OPCODE_MISC_PREFIX, "bulk-memory prefix");
         writeUleb128(os, WASM_OPCODE_DATA_DROP, "DATA.DROP");