[Wasm RyuJIT] Block stores #123738

kg · 2026-01-28T23:35:40Z

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dotnet-policy-service · 2026-01-28T23:36:29Z

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kg · 2026-01-28T23:51:31Z

Not sure what i'm doing wrong here yet.


*************** Starting PHASE Lowering nodeinfo
compEnregLocals() is false, setting doNotEnreg flag for all locals.
Local V00 should not be enregistered because: opts.compFlags & CLFLG_REGVAR is not set

Local V01 should not be enregistered because: opts.compFlags & CLFLG_REGVAR is not set

Local V02 should not be enregistered because: opts.compFlags & CLFLG_REGVAR is not set

Local V03 should not be enregistered because: opts.compFlags & CLFLG_REGVAR is not set
BB02: already in WASM value stack order
lowering store lcl var/field (before):
N001 (???,???) [000002] -----+-----                    t2 =    CNS_INT   int    0
                                                            /--*  t2     int    
N002 (???,???) [000003] DA---+-----                         *  STORE_LCL_VAR struct<Program+S, 16> V03 loc1         


Local V03 should not be enregistered because: written/read in a block op
lowering store lcl var/field (after):
N001 (???,???) [000002] -----+-----                    t2 =    CNS_INT   int    0
               [000012] D----------                   t12 =    LCL_ADDR  byref  V03 loc1         [+0]
                                                            /--*  t12    byref  
                                                            +--*  t2     int    
N002 (???,???) [000003] sA---+-----                         *  STORE_BLK struct<Program+S, 16> (init)


Local V03 should not be enregistered because: written/read in a block op
lowering return node
N001 (???,???) [000007] -----+-----                         *  RETURN    void  
============


Program:copyStruct(ptr) - NYI (Z:\runtime\src\coreclr\jit\lowerwasm.cpp:476 - NYI_WASM: IR not in a stackified form)
Z:\runtime\src\coreclr\jit\lowerwasm.cpp:476
Assertion failed 'NYI_WASM: IR not in a stackified form' in 'Program:copyStruct(ptr)' during 'Lowering nodeinfo' (IL size 17; hash 0xce1e49ee; MinOpts)

EgorBo · 2026-01-29T00:08:21Z

src/coreclr/jit/lowerwasm.cpp

+        {
+            blkNode->gtBlkOpKind = GenTreeBlk::BlkOpKindLoop;
+            src->SetContained();
+            // memory.fill


in this case it's expected to emit a loop of pointer-sized stores (with 0 value) to guarantee atomicity for gc slots (which memset does not guarantee), I am not sure it's a problem today for WASM, but it's probably better to maintain that

Copilot

Pull request overview

This PR implements infrastructure for WebAssembly block store operations in the RyuJIT compiler. It adds support for lowering block copy and initialization operations to use WASM-specific memory.copy and memory.fill instructions.

Changes:

Adds LowerBlockStore implementation for WASM target to handle block copy and initialization operations
Introduces two new WASM instructions (memory_copy and memory_fill) and their associated instruction format (IF_MEMCPY)
Adds emitter support for encoding and displaying the new IF_MEMCPY instruction format

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
src/coreclr/jit/lowerwasm.cpp	Implements LowerBlockStore to handle GT_STORE_BLK and GT_INIT_BLK operations, with partial infrastructure for memory.copy and memory.fill
src/coreclr/jit/instrswasm.h	Adds memory_copy and memory_fill instruction definitions with their opcodes
src/coreclr/jit/emitfmtswasm.h	Defines the IF_MEMCPY instruction format for memory operations with two memory indices
src/coreclr/jit/emitwasm.cpp	Implements encoding, size calculation, and display logic for IF_MEMCPY instruction format

Copilot · 2026-01-29T17:10:01Z

src/coreclr/jit/lowerwasm.cpp

+            // TODO-1stClassStructs: for now we can't work with STORE_BLOCK source in register.
+            // TODO-WASM: Is this true for wasm as well?
+            const unsigned srcLclNum = src->AsLclVar()->GetLclNum();
+            comp->lvaSetVarDoNotEnregister(srcLclNum DEBUGARG(DoNotEnregisterReason::BlockOp));


Consider using DoNotEnregisterReason::StoreBlkSrc instead of DoNotEnregisterReason::BlockOp for consistency with other architectures (see lowerxarch.cpp:473). StoreBlkSrc is more specific and indicates this is specifically for STORE_BLK sources.

Suggested change

comp->lvaSetVarDoNotEnregister(srcLclNum DEBUGARG(DoNotEnregisterReason::BlockOp));

comp->lvaSetVarDoNotEnregister(srcLclNum DEBUGARG(DoNotEnregisterReason::StoreBlkSrc));

Copilot · 2026-01-29T17:10:01Z

src/coreclr/jit/instrswasm.h

+INST(memory_copy,         "memory.copy",         0, IF_MEMCPY,  0x10FC)
+INST(memory_fill,         "memory.fill",         0, IF_ULEB128, 0x11FC)
+
+


Extra blank line should be removed for consistency with the rest of the file, which uses single blank lines between sections.

Suggested change

Copilot · 2026-01-29T17:10:02Z

src/coreclr/jit/lowerwasm.cpp

+        else
+        {
+            // memory.fill
+        }


This code path leaves blkNode->gtBlkOpKind unset (it remains BlkOpKindInvalid). When codegen encounters this node, it will fail because there's no handling for WASM memory.fill instruction yet. Either this should set an appropriate operation kind, or GT_STORE_BLK handling should be added to codegenwasm.cpp before this PR is merged.

Copilot · 2026-01-29T17:10:02Z

src/coreclr/jit/lowerwasm.cpp

+        else
+        {
+            assert(blkNode->OperIs(GT_STORE_BLK));
+            // memory.copy
+        }


This code path leaves blkNode->gtBlkOpKind unset (it remains BlkOpKindInvalid). When codegen encounters this node, it will fail because there's no handling for WASM memory.copy instruction yet. Either this should set an appropriate operation kind, or GT_STORE_BLK handling should be added to codegenwasm.cpp before this PR is merged.

Copilot · 2026-01-29T17:10:02Z

src/coreclr/jit/emitfmtswasm.h

 IF_DEF(F64,         IS_NONE, NONE) // <opcode> <f64 immediate (stored as 64-bit integer constant)>
 IF_DEF(MEMARG,      IS_NONE, NONE) // <opcode> <memarg> (<align> <offset>)
 IF_DEF(LOCAL_DECL,  IS_NONE, NONE) // <ULEB128 immediate> <byte>
+IF_DEF(MEMCPY,      IS_NONE, NONE) // <memory index> <memory index>


The comment should be <opcode> <memory index> <memory index> to be consistent with other instruction format comments that include the opcode in their description (e.g., ULEB128, SLEB128, MEMARG).

Suggested change

IF_DEF(MEMCPY, IS_NONE, NONE) // <memory index> <memory index>

IF_DEF(MEMCPY, IS_NONE, NONE) // <opcode> <memory index> <memory index>

Copilot · 2026-01-29T17:10:02Z

src/coreclr/jit/emitwasm.cpp

+        case IF_MEMCPY:
+        {
+            size += idIsCnsReloc() ? PADDED_RELOC_SIZE : SizeOfULEB128(emitGetInsSC(this));
+            size += idIsCnsReloc() ? PADDED_RELOC_SIZE : SizeOfULEB128(emitGetInsSC(this));


Missing break statement causes fall-through to the default case, which will call unreached() and cause a runtime error. This will prevent the IF_MEMCPY instruction format from working correctly.

Suggested change

size += idIsCnsReloc() ? PADDED_RELOC_SIZE : SizeOfULEB128(emitGetInsSC(this));

size += idIsCnsReloc() ? PADDED_RELOC_SIZE : SizeOfULEB128(emitGetInsSC(this));

break;

Copilot · 2026-01-29T17:10:03Z

src/coreclr/jit/emitwasm.cpp

+            cnsval_ssize_t imm = emitGetInsSC(id);
+            printf(" %llu %llu", (uint64_t)imm, (uint64_t)imm);
+            dispJumpTargetIfAny();
+        }


Missing break statement causes fall-through to the IF_LOCAL_DECL case. This will result in incorrect output when displaying IF_MEMCPY instructions, as it will also print the local declaration information.

Suggested change

}

}

break;

kg added 2 commits January 28, 2026 15:12

Checkpoint block stores

fc34424

Add insns for memory copy and fill

34c5441

kg added arch-wasm WebAssembly architecture area-CodeGen-coreclr CLR JIT compiler in src/coreclr/src/jit and related components such as SuperPMI labels Jan 28, 2026

dotnet-policy-service bot assigned kg Jan 28, 2026

Remove NYIs so stuff can flow through

22b8fbe

EgorBo reviewed Jan 29, 2026

View reviewed changes

Cleanup

7fcf407

Copilot AI review requested due to automatic review settings January 29, 2026 17:04

Copilot started reviewing on behalf of kg January 29, 2026 17:04 View session

Copilot AI reviewed Jan 29, 2026

View reviewed changes

build-analysis bot mentioned this pull request Jan 30, 2026

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[Wasm RyuJIT] Block stores #123738

[Wasm RyuJIT] Block stores #123738

kg commented Jan 28, 2026

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EgorBo Jan 29, 2026 •

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	comp->lvaSetVarDoNotEnregister(srcLclNum DEBUGARG(DoNotEnregisterReason::BlockOp));
	comp->lvaSetVarDoNotEnregister(srcLclNum DEBUGARG(DoNotEnregisterReason::StoreBlkSrc));

		INST(memory_copy, "memory.copy", 0, IF_MEMCPY, 0x10FC)
		INST(memory_fill, "memory.fill", 0, IF_ULEB128, 0x11FC)

	IF_DEF(MEMCPY, IS_NONE, NONE) // <memory index> <memory index>
	IF_DEF(MEMCPY, IS_NONE, NONE) // <opcode> <memory index> <memory index>

	size += idIsCnsReloc() ? PADDED_RELOC_SIZE : SizeOfULEB128(emitGetInsSC(this));
	size += idIsCnsReloc() ? PADDED_RELOC_SIZE : SizeOfULEB128(emitGetInsSC(this));
	break;

[Wasm RyuJIT] Block stores #123738

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Pull request overview

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