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Merged
aykevl merged 2 commits into from
May 25, 2026
Merged

Add //go:noheap #5409

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e653ef5
compiler: clean up pointer pack code
aykevl May 20, 2026
994c1c4
compiler: add //go:noheap pragma
aykevl May 20, 2026
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6 changes: 5 additions & 1 deletion builder/tools.go
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Original file line number Diff line number Diff line change
Expand Up @@ -122,12 +122,16 @@ func parseLLDErrors(text string) error {
parsedError = true
line, _ := strconv.Atoi(matches[3])
// TODO: detect common mistakes like -gc=none?
msg := "linker could not find symbol " + symbolName
if symbolName == "runtime.alloc_noheap" {
msg = "object allocated on the heap in //go:noheap function"
}
linkErrors = append(linkErrors, scanner.Error{
Pos: token.Position{
Filename: matches[2],
Line: line,
},
Msg: "linker could not find symbol " + symbolName,
Msg: msg,
})
}
}
Expand Down
17 changes: 12 additions & 5 deletions compiler/compiler.go
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Original file line number Diff line number Diff line change
Expand Up @@ -192,6 +192,16 @@ func newBuilder(c *compilerContext, irbuilder llvm.Builder, f *ssa.Function) *bu
}
}

// Return the runtime.alloc function variant.
// This is normally just "alloc", but is "alloc_noheap" if the //go:noheap
// pragma is used.
func (b *builder) allocFunc() string {
if b.info.noheap {
return "alloc_noheap"
}
return "alloc"
}

type blockInfo struct {
// entry is the LLVM basic block corresponding to the start of this *ssa.Block.
entry llvm.BasicBlock
Expand Down Expand Up @@ -314,9 +324,6 @@ func CompilePackage(moduleName string, pkg *loader.Package, ssaPkg *ssa.Package,
// Load comments such as //go:extern on globals.
c.loadASTComments(pkg)

// Predeclare the runtime.alloc function, which is used by the wordpack
// functionality.
c.getFunction(c.program.ImportedPackage("runtime").Members["alloc"].(*ssa.Function))
if c.NeedsStackObjects {
// Predeclare trackPointer, which is used everywhere we use runtime.alloc.
c.getFunction(c.program.ImportedPackage("runtime").Members["trackPointer"].(*ssa.Function))
Expand Down Expand Up @@ -2176,7 +2183,7 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
}
sizeValue := llvm.ConstInt(b.uintptrType, size, false)
layoutValue := b.createObjectLayout(typ, expr.Pos())
buf := b.createRuntimeCall("alloc", []llvm.Value{sizeValue, layoutValue}, expr.Comment)
buf := b.createRuntimeCall(b.allocFunc(), []llvm.Value{sizeValue, layoutValue}, expr.Comment)
align := b.targetData.ABITypeAlignment(typ)
buf.AddCallSiteAttribute(0, b.ctx.CreateEnumAttribute(llvm.AttributeKindID("align"), uint64(align)))
return buf, nil
Expand Down Expand Up @@ -2408,7 +2415,7 @@ func (b *builder) createExpr(expr ssa.Value) (llvm.Value, error) {
}
sliceSize := b.CreateBinOp(llvm.Mul, elemSizeValue, sliceCapCast, "makeslice.cap")
layoutValue := b.createObjectLayout(llvmElemType, expr.Pos())
slicePtr := b.createRuntimeCall("alloc", []llvm.Value{sliceSize, layoutValue}, "makeslice.buf")
slicePtr := b.createRuntimeCall(b.allocFunc(), []llvm.Value{sliceSize, layoutValue}, "makeslice.buf")
slicePtr.AddCallSiteAttribute(0, b.ctx.CreateEnumAttribute(llvm.AttributeKindID("align"), uint64(elemAlign)))

// Extend or truncate if necessary. This is safe as we've already done
Expand Down
2 changes: 1 addition & 1 deletion compiler/defer.go
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Expand Up @@ -488,7 +488,7 @@ func (b *builder) createDefer(instr *ssa.Defer) {
size := b.targetData.TypeAllocSize(deferredCallType)
sizeValue := llvm.ConstInt(b.uintptrType, size, false)
nilPtr := llvm.ConstNull(b.dataPtrType)
alloca = b.createRuntimeCall("alloc", []llvm.Value{sizeValue, nilPtr}, "defer.alloc.call")
alloca = b.createRuntimeCall(b.allocFunc(), []llvm.Value{sizeValue, nilPtr}, "defer.alloc.call")
}
if b.NeedsStackObjects {
b.trackPointer(alloca)
Expand Down
4 changes: 1 addition & 3 deletions compiler/llvm.go
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Expand Up @@ -129,11 +129,9 @@ func (b *builder) emitPointerPack(values []llvm.Value) llvm.Value {
// Packed data is bigger than a pointer, so allocate it on the heap.
sizeValue := llvm.ConstInt(b.uintptrType, size, false)
align := b.targetData.ABITypeAlignment(packedType)
alloc := b.mod.NamedFunction("runtime.alloc")
packedAlloc := b.CreateCall(alloc.GlobalValueType(), alloc, []llvm.Value{
packedAlloc := b.createRuntimeCall(b.allocFunc(), []llvm.Value{
sizeValue,
llvm.ConstNull(b.dataPtrType),
llvm.Undef(b.dataPtrType), // unused context parameter
}, "")
packedAlloc.AddCallSiteAttribute(0, b.ctx.CreateEnumAttribute(llvm.AttributeKindID("align"), uint64(align)))
if b.NeedsStackObjects {
Expand Down
6 changes: 5 additions & 1 deletion compiler/symbol.go
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Expand Up @@ -34,6 +34,7 @@ type functionInfo struct {
interrupt bool // go:interrupt
nobounds bool // go:nobounds
noescape bool // go:noescape
noheap bool // go:noheap
variadic bool // go:variadic (CGo only)
inline inlineType // go:inline
}
Expand Down Expand Up @@ -161,7 +162,7 @@ func (c *compilerContext) getFunction(fn *ssa.Function) (llvm.Type, llvm.Value)
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
case "machine.keepAliveNoEscape", "machine.unsafeNoEscape":
llvmFn.AddAttributeAtIndex(1, c.ctx.CreateEnumAttribute(llvm.AttributeKindID("nocapture"), 0))
case "runtime.alloc":
case "runtime.alloc", "runtime.alloc_noheap":
// Tell the optimizer that runtime.alloc is an allocator, meaning that it
// returns values that are never null and never alias to an existing value.
for _, attrName := range []string{"noalias", "nonnull"} {
Expand Down Expand Up @@ -476,6 +477,9 @@ func (c *compilerContext) parsePragmas(info *functionInfo, f *ssa.Function) {
if len(f.Blocks) == 0 {
info.noescape = true
}
case "//go:noheap":
// Ensure this function does not allocate on the heap.
info.noheap = true
case "//go:variadic":
// The //go:variadic pragma is emitted by the CGo preprocessing
// pass for C variadic functions. This includes both explicit
Expand Down
62 changes: 29 additions & 33 deletions compiler/testdata/basic.ll
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Expand Up @@ -10,33 +10,30 @@ target triple = "wasm32-unknown-wasi"
@main.a = hidden global { ptr, i32, i32 } zeroinitializer, align 4
@main.b = hidden global [2 x ptr] zeroinitializer, align 4

; Function Attrs: allockind("alloc,zeroed") allocsize(0)
declare noalias nonnull ptr @runtime.alloc(i32, ptr, ptr) #0

declare void @runtime.trackPointer(ptr nocapture readonly, ptr, ptr) #1
declare void @runtime.trackPointer(ptr nocapture readonly, ptr, ptr) #0

; Function Attrs: nounwind
define hidden void @main.init(ptr %context) unnamed_addr #2 {
define hidden void @main.init(ptr %context) unnamed_addr #1 {
entry:
ret void
}

; Function Attrs: nounwind
define hidden i32 @main.addInt(i32 %x, i32 %y, ptr %context) unnamed_addr #2 {
define hidden i32 @main.addInt(i32 %x, i32 %y, ptr %context) unnamed_addr #1 {
entry:
%0 = add i32 %x, %y
ret i32 %0
}

; Function Attrs: nounwind
define hidden i1 @main.equalInt(i32 %x, i32 %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.equalInt(i32 %x, i32 %y, ptr %context) unnamed_addr #1 {
entry:
%0 = icmp eq i32 %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden i32 @main.divInt(i32 %x, i32 %y, ptr %context) unnamed_addr #2 {
define hidden i32 @main.divInt(i32 %x, i32 %y, ptr %context) unnamed_addr #1 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
Expand All @@ -50,14 +47,14 @@ divbyzero.next: ; preds = %entry
ret i32 %5

divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(ptr undef) #3
call void @runtime.divideByZeroPanic(ptr undef) #2
unreachable
}

declare void @runtime.divideByZeroPanic(ptr) #1
declare void @runtime.divideByZeroPanic(ptr) #0

; Function Attrs: nounwind
define hidden i32 @main.divUint(i32 %x, i32 %y, ptr %context) unnamed_addr #2 {
define hidden i32 @main.divUint(i32 %x, i32 %y, ptr %context) unnamed_addr #1 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
Expand All @@ -67,12 +64,12 @@ divbyzero.next: ; preds = %entry
ret i32 %1

divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(ptr undef) #3
call void @runtime.divideByZeroPanic(ptr undef) #2
unreachable
}

; Function Attrs: nounwind
define hidden i32 @main.remInt(i32 %x, i32 %y, ptr %context) unnamed_addr #2 {
define hidden i32 @main.remInt(i32 %x, i32 %y, ptr %context) unnamed_addr #1 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
Expand All @@ -86,12 +83,12 @@ divbyzero.next: ; preds = %entry
ret i32 %5

divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(ptr undef) #3
call void @runtime.divideByZeroPanic(ptr undef) #2
unreachable
}

; Function Attrs: nounwind
define hidden i32 @main.remUint(i32 %x, i32 %y, ptr %context) unnamed_addr #2 {
define hidden i32 @main.remUint(i32 %x, i32 %y, ptr %context) unnamed_addr #1 {
entry:
%0 = icmp eq i32 %y, 0
br i1 %0, label %divbyzero.throw, label %divbyzero.next
Expand All @@ -101,66 +98,66 @@ divbyzero.next: ; preds = %entry
ret i32 %1

divbyzero.throw: ; preds = %entry
call void @runtime.divideByZeroPanic(ptr undef) #3
call void @runtime.divideByZeroPanic(ptr undef) #2
unreachable
}

; Function Attrs: nounwind
define hidden i1 @main.floatEQ(float %x, float %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.floatEQ(float %x, float %y, ptr %context) unnamed_addr #1 {
entry:
%0 = fcmp oeq float %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden i1 @main.floatNE(float %x, float %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.floatNE(float %x, float %y, ptr %context) unnamed_addr #1 {
entry:
%0 = fcmp une float %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden i1 @main.floatLower(float %x, float %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.floatLower(float %x, float %y, ptr %context) unnamed_addr #1 {
entry:
%0 = fcmp olt float %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden i1 @main.floatLowerEqual(float %x, float %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.floatLowerEqual(float %x, float %y, ptr %context) unnamed_addr #1 {
entry:
%0 = fcmp ole float %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden i1 @main.floatGreater(float %x, float %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.floatGreater(float %x, float %y, ptr %context) unnamed_addr #1 {
entry:
%0 = fcmp ogt float %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden i1 @main.floatGreaterEqual(float %x, float %y, ptr %context) unnamed_addr #2 {
define hidden i1 @main.floatGreaterEqual(float %x, float %y, ptr %context) unnamed_addr #1 {
entry:
%0 = fcmp oge float %x, %y
ret i1 %0
}

; Function Attrs: nounwind
define hidden float @main.complexReal(float %x.r, float %x.i, ptr %context) unnamed_addr #2 {
define hidden float @main.complexReal(float %x.r, float %x.i, ptr %context) unnamed_addr #1 {
entry:
ret float %x.r
}

; Function Attrs: nounwind
define hidden float @main.complexImag(float %x.r, float %x.i, ptr %context) unnamed_addr #2 {
define hidden float @main.complexImag(float %x.r, float %x.i, ptr %context) unnamed_addr #1 {
entry:
ret float %x.i
}

; Function Attrs: nounwind
define hidden { float, float } @main.complexAdd(float %x.r, float %x.i, float %y.r, float %y.i, ptr %context) unnamed_addr #2 {
define hidden { float, float } @main.complexAdd(float %x.r, float %x.i, float %y.r, float %y.i, ptr %context) unnamed_addr #1 {
entry:
%0 = fadd float %x.r, %y.r
%1 = fadd float %x.i, %y.i
Expand All @@ -170,7 +167,7 @@ entry:
}

; Function Attrs: nounwind
define hidden { float, float } @main.complexSub(float %x.r, float %x.i, float %y.r, float %y.i, ptr %context) unnamed_addr #2 {
define hidden { float, float } @main.complexSub(float %x.r, float %x.i, float %y.r, float %y.i, ptr %context) unnamed_addr #1 {
entry:
%0 = fsub float %x.r, %y.r
%1 = fsub float %x.i, %y.i
Expand All @@ -180,7 +177,7 @@ entry:
}

; Function Attrs: nounwind
define hidden { float, float } @main.complexMul(float %x.r, float %x.i, float %y.r, float %y.i, ptr %context) unnamed_addr #2 {
define hidden { float, float } @main.complexMul(float %x.r, float %x.i, float %y.r, float %y.i, ptr %context) unnamed_addr #1 {
entry:
%0 = fmul float %x.r, %y.r
%1 = fmul float %x.i, %y.i
Expand All @@ -194,19 +191,18 @@ entry:
}

; Function Attrs: nounwind
define hidden void @main.foo(ptr %context) unnamed_addr #2 {
define hidden void @main.foo(ptr %context) unnamed_addr #1 {
entry:
call void @"main.foo$1"(%main.kv.0 zeroinitializer, ptr undef)
ret void
}

; Function Attrs: nounwind
define internal void @"main.foo$1"(%main.kv.0 %b, ptr %context) unnamed_addr #2 {
define internal void @"main.foo$1"(%main.kv.0 %b, ptr %context) unnamed_addr #1 {
entry:
ret void
}

attributes #0 = { allockind("alloc,zeroed") allocsize(0) "alloc-family"="runtime.alloc" "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
attributes #1 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
attributes #2 = { nounwind "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
attributes #3 = { nounwind }
attributes #0 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
attributes #1 = { nounwind "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
attributes #2 = { nounwind }
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