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The new implementation has several benefits compared to the old C++ implementation: * It is significantly simpler. It optimizes each load separately instead of all at once with bit-field based dataflow. * It's using alias analysis more accurately which enables more loads to be optimized * It avoids inserting additional copies in OSSA The algorithm is a data flow analysis which starts at the original load and searches for preceding stores or loads by following the control flow in backward direction. The preceding stores and loads provide the "available values" with which the original load can be replaced.
42 lines
1.2 KiB
Plaintext
42 lines
1.2 KiB
Plaintext
// RUN: %target-sil-opt -enable-sil-verify-all %s -redundant-load-elimination | %FileCheck %s
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sil_stage canonical
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import Builtin
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struct MyStruct {
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var value: Builtin.FPIEEE64
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}
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enum MyEnum {
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case some(MyStruct)
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case none
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}
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// Check if alias analysis can handle unchecked_take_enum_data_addr correctly
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// and does not crash with a stack overflow.
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// CHECK-LABEL: sil @testit
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// CHECK: load
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// CHECK: load
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// CHECK: return
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sil @testit : $@convention(method) (MyEnum) -> Builtin.FPIEEE64 {
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bb0(%0 : $MyEnum):
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%x1 = alloc_stack $MyEnum
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store %0 to %x1 : $*MyEnum
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%x7 = unchecked_take_enum_data_addr %x1 : $*MyEnum, #MyEnum.some!enumelt
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%x8 = struct_element_addr %x7 : $*MyStruct, #MyStruct.value
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%x11 = alloc_stack $MyEnum
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store %0 to %x11 : $*MyEnum
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%x19 = unchecked_take_enum_data_addr %x11 : $*MyEnum, #MyEnum.some!enumelt
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%x20 = struct_element_addr %x19 : $*MyStruct, #MyStruct.value
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%x24 = load %x20 : $*Builtin.FPIEEE64
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%x27 = load %x8 : $*Builtin.FPIEEE64
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%x28 = builtin "fsub_FPIEEE64"(%x27 : $Builtin.FPIEEE64, %x24 : $Builtin.FPIEEE64) : $Builtin.FPIEEE64
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dealloc_stack %x11 : $*MyEnum
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dealloc_stack %x1 : $*MyEnum
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return %x28 : $Builtin.FPIEEE64
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}
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