8a84b285f6
In simplifycfg/cvp/sccp, we eliminate dead edges of switches according to the knownbits/range info of conditions. However, these approximations may not meet the real-world needs when the domain of condition values is sparse. For example, if the condition can only be either -3 or 3, we cannot prove that the condition never evaluates to 1 (knownbits: ???????1, range: [-3, 4)). This patch adds a helper function `collectPossibleValues` to enumerate all the possible values of V. To fix the motivating issue, `eliminateDeadSwitchCases` will use the result to remove dead edges. Note: In https://discourse.llvm.org/t/missed-optimization-due-to-overflow-check/88700 I proposed a new value lattice kind to represent such values. But I find it hard to apply because the transition becomes much complicated. Compile-time impact looks neutral: https://llvm-compile-time-tracker.com/compare.php?from=32d6b2139a6c8f79e074e8c6cfe0cc9e79c4c0c8&to=e47c26e3f1bf9eb062684dda4fafce58438e994b&stat=instructions:u This patch removes many dead error-handling codes: https://github.com/dtcxzyw/llvm-opt-benchmark/pull/3012 Closes https://github.com/llvm/llvm-project/issues/165179.
31 lines
1.1 KiB
LLVM
31 lines
1.1 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt %s -keep-loops=false -switch-to-lookup=true -passes=simplifycfg -simplifycfg-require-and-preserve-domtree=1 -S | FileCheck %s
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; RUN: opt %s -passes='simplifycfg<no-keep-loops;switch-to-lookup>' -S | FileCheck %s
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define void @f6() #0 {
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; CHECK-LABEL: @f6(
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; CHECK-NEXT: entry:
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; CHECK-NEXT: br label [[F1_EXIT_I:%.*]]
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; CHECK: f1.exit.i:
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; CHECK-NEXT: [[TOBOOL7_I:%.*]] = icmp ne i16 1, 0
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; CHECK-NEXT: br label [[F1_EXIT_I]]
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;
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entry:
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br label %for.cond.i
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for.cond.i: ; preds = %f1.exit.i, %entry
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switch i16 undef, label %f1.exit.i [
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i16 -1, label %cond.false.i3.i
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i16 1, label %cond.false.i3.i
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i16 0, label %cond.false.i3.i
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]
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cond.false.i3.i: ; preds = %for.cond.i, %for.cond.i, %for.cond.i
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br label %f1.exit.i
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f1.exit.i: ; preds = %cond.false.i3.i, %for.cond.i
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%cond.i4.i = phi i16 [ undef, %cond.false.i3.i ], [ 1, %for.cond.i ]
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%tobool7.i = icmp ne i16 %cond.i4.i, 0
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br label %for.cond.i
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}
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