8e7461e29a
This should be generally good for a lot of LSV cases, but the attached test demonstrates a specific compile time issue that appears in the event where the `CaptureTracking` default max uses is raised. Without using batching alias analysis, this test takes 6 seconds to compile in a release build. With, less than a second. This is because the mechanism that proves `NoAlias` in this case is very expensive (`CaptureTracking.cpp`), and caching the result leads to 2 calls to that mechanism instead of ~300,000 (run with -stats to see the difference) This test only demonstrates the compile time issue if `capture-tracking-max-uses-to-explore` is set to at least 1024, because with the default value of 100, the `CaptureTracking` analysis is not run, `NoAlias` is not proven, and the vectorizer gives up early.
61 lines
2.3 KiB
LLVM
61 lines
2.3 KiB
LLVM
; RUN: opt -S < %s -passes='loop-unroll,load-store-vectorizer' -unroll-count=128 --capture-tracking-max-uses-to-explore=1024 | FileCheck %s
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; Without using batching alias analysis, this test takes 6 seconds to compile. With, less than a second.
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; This is because the mechanism that proves NoAlias in this case is very expensive (CaptureTracking.cpp),
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; and caching the result leads to 2 calls to that mechanism instead of ~300,000 (run with -stats to see the difference)
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; This test only demonstrates the compile time issue if capture-tracking-max-uses-to-explore is set to at least 1024,
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; because with the default value of 100, the CaptureTracking analysis is not run, NoAlias is not proven, and the vectorizer gives up early.
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@global_mem = external global i8, align 4
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define void @compile-time-test() {
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; CHECK-LABEL: define void @compile-time-test() {
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; CHECK-COUNT-128: load <4 x i8>
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entry:
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; Create base pointer to a global variable with the inefficient pattern that Alias Analysis cannot easily traverse through.
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%global_base_loads = getelementptr i8, ptr inttoptr (i32 ptrtoint (ptr @global_mem to i32) to ptr), i64 0
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; Create another pointer for the stores.
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%local_base_stores = alloca <512 x i8>, align 4
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; 512 interwoven loads and stores in a loop that gets unrolled
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br label %loop
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loop:
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%i = phi i64 [ 0, %entry ], [ %i_next, %loop ]
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%ptr_0 = getelementptr i8, ptr %global_base_loads, i64 %i
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%load_0 = load i8, ptr %ptr_0, align 4
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%ptr2_0 = getelementptr i8, ptr %local_base_stores, i64 %i
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store i8 %load_0, ptr %ptr2_0, align 4
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%i_1 = add i64 %i, 1
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%ptr_1 = getelementptr i8, ptr %global_base_loads, i64 %i_1
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%load_1 = load i8, ptr %ptr_1, align 1
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%ptr2_1 = getelementptr i8, ptr %local_base_stores, i64 %i_1
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store i8 %load_1, ptr %ptr2_1, align 1
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%i_2 = add i64 %i, 2
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%ptr_2 = getelementptr i8, ptr %global_base_loads, i64 %i_2
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%load_2 = load i8, ptr %ptr_2, align 2
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%ptr2_2 = getelementptr i8, ptr %local_base_stores, i64 %i_2
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store i8 %load_2, ptr %ptr2_2, align 2
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%i_3 = add i64 %i, 3
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%ptr_3 = getelementptr i8, ptr %global_base_loads, i64 %i_3
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%load_3 = load i8, ptr %ptr_3, align 1
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%ptr2_3 = getelementptr i8, ptr %local_base_stores, i64 %i_3
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store i8 %load_3, ptr %ptr2_3, align 1
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%i_next = add i64 %i, 4
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%cmp = icmp ult i64 %i_next, 512
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br i1 %cmp, label %loop, label %done
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done:
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ret void
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}
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