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authorAyke van Laethem <[email protected]>2024-06-25 20:14:05 +0200
committerRon Evans <[email protected]>2024-07-03 07:31:37 +0200
commite6caa3fe9ef0a68779953b7fc9c3cfce3c8158ca (patch)
tree8e05be159e60af3f1cc17df7f8b571d4e33d67ee
parent571447c7c14774dd4fe4342a35eee024aca2578a (diff)
downloadtinygo-e6caa3fe9ef0a68779953b7fc9c3cfce3c8158ca.tar.gz
tinygo-e6caa3fe9ef0a68779953b7fc9c3cfce3c8158ca.zip
transform: fix incorrect alignment of heap-to-stack transform
It assumed the maximum alignment was equal to sizeof(void*), which is definitely not the case. So this only worked more or less by accident previously. It now uses the alignment as specified by the frontend, or else `unsafe.Alignof(complex128)` which is typically the maximum alignment of a given platform (though this shouldn't really happen in practice: the optimizer should keep the 'align' attribute in place).
-rw-r--r--go.mod2
-rw-r--r--go.sum4
-rw-r--r--transform/allocs.go31
-rw-r--r--transform/testdata/allocs.ll31
-rw-r--r--transform/testdata/allocs.out.ll25
5 files changed, 62 insertions, 31 deletions
diff --git a/go.mod b/go.mod
index d17f62e3f..b054e77b6 100644
--- a/go.mod
+++ b/go.mod
@@ -21,7 +21,7 @@ require (
golang.org/x/sys v0.21.0
golang.org/x/tools v0.22.1-0.20240621165957-db513b091504
gopkg.in/yaml.v2 v2.4.0
- tinygo.org/x/go-llvm v0.0.0-20240518103902-697964f2a9dc
+ tinygo.org/x/go-llvm v0.0.0-20240627184919-3b50c76783a8
)
require (
diff --git a/go.sum b/go.sum
index c093ee07c..8d6dc516c 100644
--- a/go.sum
+++ b/go.sum
@@ -106,5 +106,5 @@ gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-tinygo.org/x/go-llvm v0.0.0-20240518103902-697964f2a9dc h1:TCzibFa4oLu+njEP3fnRUmZ+QQeb8BjtOwctgcjzL0k=
-tinygo.org/x/go-llvm v0.0.0-20240518103902-697964f2a9dc/go.mod h1:GFbusT2VTA4I+l4j80b17KFK+6whv69Wtny5U+T8RR0=
+tinygo.org/x/go-llvm v0.0.0-20240627184919-3b50c76783a8 h1:bLsZXRUBavt++CJlMN7sppNziqu3LyamESLhFJcpqFQ=
+tinygo.org/x/go-llvm v0.0.0-20240627184919-3b50c76783a8/go.mod h1:GFbusT2VTA4I+l4j80b17KFK+6whv69Wtny5U+T8RR0=
diff --git a/transform/allocs.go b/transform/allocs.go
index 67ca1ea43..870faa5b7 100644
--- a/transform/allocs.go
+++ b/transform/allocs.go
@@ -29,10 +29,14 @@ func OptimizeAllocs(mod llvm.Module, printAllocs *regexp.Regexp, maxStackAlloc u
targetData := llvm.NewTargetData(mod.DataLayout())
defer targetData.Dispose()
- ptrType := llvm.PointerType(mod.Context().Int8Type(), 0)
- builder := mod.Context().NewBuilder()
+ ctx := mod.Context()
+ builder := ctx.NewBuilder()
defer builder.Dispose()
+ // Determine the maximum alignment on this platform.
+ complex128Type := ctx.StructType([]llvm.Type{ctx.DoubleType(), ctx.DoubleType()}, false)
+ maxAlign := int64(targetData.ABITypeAlignment(complex128Type))
+
for _, heapalloc := range getUses(allocator) {
logAllocs := printAllocs != nil && printAllocs.MatchString(heapalloc.InstructionParent().Parent().Name())
if heapalloc.Operand(0).IsAConstantInt().IsNil() {
@@ -90,21 +94,14 @@ func OptimizeAllocs(mod llvm.Module, printAllocs *regexp.Regexp, maxStackAlloc u
}
// The pointer value does not escape.
- // Determine the appropriate alignment of the alloca. The size of the
- // allocation gives us a hint what the alignment should be.
- var alignment int
- if size%2 != 0 {
- alignment = 1
- } else if size%4 != 0 {
- alignment = 2
- } else if size%8 != 0 {
- alignment = 4
- } else {
- alignment = 8
- }
- if pointerAlignment := targetData.ABITypeAlignment(ptrType); pointerAlignment < alignment {
- // Use min(alignment, alignof(void*)) as the alignment.
- alignment = pointerAlignment
+ // Determine the appropriate alignment of the alloca.
+ attr := heapalloc.GetCallSiteEnumAttribute(0, llvm.AttributeKindID("align"))
+ alignment := int(maxAlign)
+ if !attr.IsNil() {
+ // 'align' return value attribute is set, so use it.
+ // This is basically always the case, but to be sure we'll default
+ // to maxAlign if it isn't.
+ alignment = int(attr.GetEnumValue())
}
// Insert alloca in the entry block. Do it here so that mem2reg can
diff --git a/transform/testdata/allocs.ll b/transform/testdata/allocs.ll
index 1c2fdd5aa..4f6960ef9 100644
--- a/transform/testdata/allocs.ll
+++ b/transform/testdata/allocs.ll
@@ -7,7 +7,7 @@ declare nonnull ptr @runtime.alloc(i32, ptr)
; Test allocating a single int (i32) that should be allocated on the stack.
define void @testInt() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
store i32 5, ptr %alloc
ret void
}
@@ -15,7 +15,7 @@ define void @testInt() {
; Test allocating an array of 3 i16 values that should be allocated on the
; stack.
define i16 @testArray() {
- %alloc = call ptr @runtime.alloc(i32 6, ptr null)
+ %alloc = call align 2 ptr @runtime.alloc(i32 6, ptr null)
%alloc.1 = getelementptr i16, ptr %alloc, i32 1
store i16 5, ptr %alloc.1
%alloc.2 = getelementptr i16, ptr %alloc, i32 2
@@ -23,30 +23,45 @@ define i16 @testArray() {
ret i16 %val
}
+; Test allocating objects with an unknown alignment.
+define void @testUnknownAlign() {
+ %alloc32 = call ptr @runtime.alloc(i32 32, ptr null)
+ store i8 5, ptr %alloc32
+ %alloc24 = call ptr @runtime.alloc(i32 24, ptr null)
+ store i16 5, ptr %alloc24
+ %alloc12 = call ptr @runtime.alloc(i32 12, ptr null)
+ store i16 5, ptr %alloc12
+ %alloc6 = call ptr @runtime.alloc(i32 6, ptr null)
+ store i16 5, ptr %alloc6
+ %alloc3 = call ptr @runtime.alloc(i32 3, ptr null)
+ store i16 5, ptr %alloc3
+ ret void
+}
+
; Call a function that will let the pointer escape, so the heap-to-stack
; transform shouldn't be applied.
define void @testEscapingCall() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
%val = call ptr @escapeIntPtr(ptr %alloc)
ret void
}
define void @testEscapingCall2() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
%val = call ptr @escapeIntPtrSometimes(ptr %alloc, ptr %alloc)
ret void
}
; Call a function that doesn't let the pointer escape.
define void @testNonEscapingCall() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
%val = call ptr @noescapeIntPtr(ptr %alloc)
ret void
}
; Return the allocated value, which lets it escape.
define ptr @testEscapingReturn() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
ret ptr %alloc
}
@@ -55,7 +70,7 @@ define void @testNonEscapingLoop() {
entry:
br label %loop
loop:
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
%ptr = call ptr @noescapeIntPtr(ptr %alloc)
%result = icmp eq ptr null, %ptr
br i1 %result, label %loop, label %end
@@ -65,7 +80,7 @@ end:
; Test a zero-sized allocation.
define void @testZeroSizedAlloc() {
- %alloc = call ptr @runtime.alloc(i32 0, ptr null)
+ %alloc = call align 1 ptr @runtime.alloc(i32 0, ptr null)
%ptr = call ptr @noescapeIntPtr(ptr %alloc)
ret void
}
diff --git a/transform/testdata/allocs.out.ll b/transform/testdata/allocs.out.ll
index b3c8bf8f3..e4a5e4f7e 100644
--- a/transform/testdata/allocs.out.ll
+++ b/transform/testdata/allocs.out.ll
@@ -22,14 +22,33 @@ define i16 @testArray() {
ret i16 %val
}
+define void @testUnknownAlign() {
+ %stackalloc4 = alloca [32 x i8], align 8
+ %stackalloc3 = alloca [24 x i8], align 8
+ %stackalloc2 = alloca [12 x i8], align 8
+ %stackalloc1 = alloca [6 x i8], align 8
+ %stackalloc = alloca [3 x i8], align 8
+ store [32 x i8] zeroinitializer, ptr %stackalloc4, align 8
+ store i8 5, ptr %stackalloc4, align 1
+ store [24 x i8] zeroinitializer, ptr %stackalloc3, align 8
+ store i16 5, ptr %stackalloc3, align 2
+ store [12 x i8] zeroinitializer, ptr %stackalloc2, align 8
+ store i16 5, ptr %stackalloc2, align 2
+ store [6 x i8] zeroinitializer, ptr %stackalloc1, align 8
+ store i16 5, ptr %stackalloc1, align 2
+ store [3 x i8] zeroinitializer, ptr %stackalloc, align 8
+ store i16 5, ptr %stackalloc, align 2
+ ret void
+}
+
define void @testEscapingCall() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
%val = call ptr @escapeIntPtr(ptr %alloc)
ret void
}
define void @testEscapingCall2() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
%val = call ptr @escapeIntPtrSometimes(ptr %alloc, ptr %alloc)
ret void
}
@@ -42,7 +61,7 @@ define void @testNonEscapingCall() {
}
define ptr @testEscapingReturn() {
- %alloc = call ptr @runtime.alloc(i32 4, ptr null)
+ %alloc = call align 4 ptr @runtime.alloc(i32 4, ptr null)
ret ptr %alloc
}