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compiler: create temporary allocas with appropriate lifetimes

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Make sure all allocas are created in the entry block and are given the
right lifetimes. This is good for code quality:

  * Moving allocas to the entry block makes sure they are always
    allocated statically (avoiding the need for a frame pointer) and do
    not grow the stack on each new alloca instruction. This is
    especially useful in loops where it could otherwise lead to a stack
    overflow even though there is no recursion.
  * Adding lifetime markers allows LLVM to reuse stack areas for
    different allocas as long as their lifetimes do not overlap.

All in all, this reduces code size in all tested cases for the BBC
micro:bit, and reduces code size for most cases for WebAssembly.
This commit is contained in:
Ayke van Laethem
2019-05-19 18:36:27 +02:00
committed by Ron Evans
parent de032cddd2
commit 7b6ef65fe7
5 changed files with 81 additions and 56 deletions
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compiler/map.go
+10 -10
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@@ -15,7 +15,7 @@ func (c *Compiler) emitMapLookup(keyType, valueType types.Type, m, key llvm.Valu
// Allocate the memory for the resulting type. Do not zero this memory: it
// will be zeroed by the hashmap get implementation if the key is not
// present in the map.
mapValueAlloca, mapValuePtr, mapValueSize := c.createEntryBlockAlloca(llvmValueType, "hashmap.value")
mapValueAlloca, mapValuePtr, mapValueSize := c.createTemporaryAlloca(llvmValueType, "hashmap.value")
// Do the lookup. How it is done depends on the key type.
var commaOkValue llvm.Value
@@ -27,12 +27,12 @@ func (c *Compiler) emitMapLookup(keyType, valueType types.Type, m, key llvm.Valu
// key can be compared with runtime.memequal
// Store the key in an alloca, in the entry block to avoid dynamic stack
// growth.
mapKeyAlloca, mapKeyPtr, mapKeySize := c.createEntryBlockAlloca(key.Type(), "hashmap.key")
mapKeyAlloca, mapKeyPtr, mapKeySize := c.createTemporaryAlloca(key.Type(), "hashmap.key")
c.builder.CreateStore(key, mapKeyAlloca)
// Fetch the value from the hashmap.
params := []llvm.Value{m, mapKeyPtr, mapValuePtr}
commaOkValue = c.createRuntimeCall("hashmapBinaryGet", params, "")
c.builder.CreateCall(c.getLifetimeEndFunc(), []llvm.Value{mapKeySize, mapKeyPtr}, "")
c.emitLifetimeEnd(mapKeyPtr, mapKeySize)
} else {
// Not trivially comparable using memcmp.
return llvm.Value{}, c.makeError(pos, "only strings, bools, ints or structs of bools/ints are supported as map keys, but got: "+keyType.String())
@@ -41,7 +41,7 @@ func (c *Compiler) emitMapLookup(keyType, valueType types.Type, m, key llvm.Valu
// Load the resulting value from the hashmap. The value is set to the zero
// value if the key doesn't exist in the hashmap.
mapValue := c.builder.CreateLoad(mapValueAlloca, "")
c.builder.CreateCall(c.getLifetimeEndFunc(), []llvm.Value{mapValueSize, mapValuePtr}, "")
c.emitLifetimeEnd(mapValuePtr, mapValueSize)
if commaOk {
tuple := llvm.Undef(c.ctx.StructType([]llvm.Type{llvmValueType, c.ctx.Int1Type()}, false))
@@ -54,7 +54,7 @@ func (c *Compiler) emitMapLookup(keyType, valueType types.Type, m, key llvm.Valu
}
func (c *Compiler) emitMapUpdate(keyType types.Type, m, key, value llvm.Value, pos token.Pos) {
valueAlloca, valuePtr, valueSize := c.createEntryBlockAlloca(value.Type(), "hashmap.value")
valueAlloca, valuePtr, valueSize := c.createTemporaryAlloca(value.Type(), "hashmap.value")
c.builder.CreateStore(value, valueAlloca)
keyType = keyType.Underlying()
if t, ok := keyType.(*types.Basic); ok && t.Info()&types.IsString != 0 {
@@ -63,15 +63,15 @@ func (c *Compiler) emitMapUpdate(keyType types.Type, m, key, value llvm.Value, p
c.createRuntimeCall("hashmapStringSet", params, "")
} else if hashmapIsBinaryKey(keyType) {
// key can be compared with runtime.memequal
keyAlloca, keyPtr, keySize := c.createEntryBlockAlloca(key.Type(), "hashmap.key")
keyAlloca, keyPtr, keySize := c.createTemporaryAlloca(key.Type(), "hashmap.key")
c.builder.CreateStore(key, keyAlloca)
params := []llvm.Value{m, keyPtr, valuePtr}
c.createRuntimeCall("hashmapBinarySet", params, "")
c.builder.CreateCall(c.getLifetimeEndFunc(), []llvm.Value{keySize, keyPtr}, "")
c.emitLifetimeEnd(keyPtr, keySize)
} else {
c.addError(pos, "only strings, bools, ints or structs of bools/ints are supported as map keys, but got: "+keyType.String())
}
c.builder.CreateCall(c.getLifetimeEndFunc(), []llvm.Value{valueSize, valuePtr}, "")
c.emitLifetimeEnd(valuePtr, valueSize)
}
func (c *Compiler) emitMapDelete(keyType types.Type, m, key llvm.Value, pos token.Pos) error {
@@ -82,11 +82,11 @@ func (c *Compiler) emitMapDelete(keyType types.Type, m, key llvm.Value, pos toke
c.createRuntimeCall("hashmapStringDelete", params, "")
return nil
} else if hashmapIsBinaryKey(keyType) {
keyAlloca, keyPtr, keySize := c.createEntryBlockAlloca(key.Type(), "hashmap.key")
keyAlloca, keyPtr, keySize := c.createTemporaryAlloca(key.Type(), "hashmap.key")
c.builder.CreateStore(key, keyAlloca)
params := []llvm.Value{m, keyPtr}
c.createRuntimeCall("hashmapBinaryDelete", params, "")
c.builder.CreateCall(c.getLifetimeEndFunc(), []llvm.Value{keySize, keyPtr}, "")
c.emitLifetimeEnd(keyPtr, keySize)
return nil
} else {
return c.makeError(pos, "only strings, bools, ints or structs of bools/ints are supported as map keys, but got: "+keyType.String())