fbcf8a8cbb
The constraint system used for ConstraintElimination assumes all varibles to be signed. This can cause missed optimization in the unsigned system, due to missing the information that all variables are unsigned (non-negative). Variables can be marked as non-negative by adding Var >= 0 for all variables. This is done for arguments on ConstraintInfo construction and after adding new variables. This handles cases like the ones outlined in https://discourse.llvm.org/t/why-does-llvm-not-perform-range-analysis-on-integer-values/74341 The original example shared above is now handled without this change, but adding another variable means that instcombine won't be able to simplify examples like https://godbolt.org/z/hTnra7zdY Adding the extra variables comes with a slight compile-time increase https://llvm-compile-time-tracker.com/compare.php?from=7568b36a2bc1a1e496ec29246966ffdfc3a8b87f&to=641a47f0acce7755e340447386013a2e086f03d9&stat=instructions:u stage1-O3 stage1-ReleaseThinLTO stage1-ReleaseLTO-g stage1-O0-g +0.04% +0.07% +0.05% +0.02% stage2-O3 stage2-O0-g stage2-clang +0.05% +0.05% +0.05% https://github.com/llvm/llvm-project/pull/76262
80 lines
2.8 KiB
LLVM
80 lines
2.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -passes=constraint-elimination -S %s | FileCheck --check-prefixes=COMMON,SIMP %s
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; RUN: opt -passes=constraint-elimination -constraint-elimination-max-rows=9 -S %s | FileCheck --check-prefixes=COMMON,SIMP %s
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; RUN: opt -passes=constraint-elimination -constraint-elimination-max-rows=8 -S %s | FileCheck --check-prefixes=COMMON,NOSIMP %s
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define i1 @test_max_row_limit(i32 %l0, i32 %l1, i32 %l2, i32 %l3, i32 %l4) {
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; SIMP-LABEL: @test_max_row_limit(
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; SIMP-NEXT: bb0:
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; SIMP-NEXT: [[C0:%.*]] = icmp uge i32 [[L0:%.*]], 100
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; SIMP-NEXT: br i1 [[C0]], label [[BB1:%.*]], label [[EXIT:%.*]]
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; SIMP: bb1:
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; SIMP-NEXT: [[C1:%.*]] = icmp uge i32 [[L1:%.*]], 100
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; SIMP-NEXT: br i1 [[C1]], label [[BB2:%.*]], label [[EXIT]]
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; SIMP: bb2:
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; SIMP-NEXT: [[C2:%.*]] = icmp uge i32 [[L2:%.*]], 100
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; SIMP-NEXT: br i1 [[C2]], label [[BB3:%.*]], label [[EXIT]]
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; SIMP: bb3:
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; SIMP-NEXT: [[C3:%.*]] = icmp uge i32 [[L3:%.*]], 100
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; SIMP-NEXT: br i1 [[C3]], label [[BB4:%.*]], label [[EXIT]]
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; SIMP: bb4:
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; SIMP-NEXT: [[C4:%.*]] = icmp uge i32 [[L4:%.*]], 100
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; SIMP-NEXT: br i1 [[C4]], label [[BB5:%.*]], label [[EXIT]]
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; SIMP: bb5:
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; SIMP-NEXT: ret i1 true
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; SIMP: exit:
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; SIMP-NEXT: ret i1 false
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;
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; NOSIMP-LABEL: @test_max_row_limit(
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; NOSIMP-NEXT: bb0:
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; NOSIMP-NEXT: [[C0:%.*]] = icmp uge i32 [[L0:%.*]], 100
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; NOSIMP-NEXT: br i1 [[C0]], label [[BB1:%.*]], label [[EXIT:%.*]]
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; NOSIMP: bb1:
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; NOSIMP-NEXT: [[C1:%.*]] = icmp uge i32 [[L1:%.*]], 100
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; NOSIMP-NEXT: br i1 [[C1]], label [[BB2:%.*]], label [[EXIT]]
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; NOSIMP: bb2:
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; NOSIMP-NEXT: [[C2:%.*]] = icmp uge i32 [[L2:%.*]], 100
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; NOSIMP-NEXT: br i1 [[C2]], label [[BB3:%.*]], label [[EXIT]]
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; NOSIMP: bb3:
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; NOSIMP-NEXT: [[C3:%.*]] = icmp uge i32 [[L3:%.*]], 100
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; NOSIMP-NEXT: br i1 [[C3]], label [[BB4:%.*]], label [[EXIT]]
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; NOSIMP: bb4:
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; NOSIMP-NEXT: [[C4:%.*]] = icmp uge i32 [[L4:%.*]], 100
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; NOSIMP-NEXT: br i1 [[C4]], label [[BB5:%.*]], label [[EXIT]]
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; NOSIMP: bb5:
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; NOSIMP-NEXT: [[C5:%.*]] = icmp uge i32 [[L4]], 100
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; NOSIMP-NEXT: ret i1 [[C5]]
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; NOSIMP: exit:
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; NOSIMP-NEXT: ret i1 false
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;
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bb0:
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%c0 = icmp uge i32 %l0, 100
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br i1 %c0, label %bb1, label %exit
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bb1:
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%c1 = icmp uge i32 %l1, 100
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br i1 %c1, label %bb2, label %exit
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bb2:
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%c2 = icmp uge i32 %l2, 100
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br i1 %c2, label %bb3, label %exit
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bb3:
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%c3 = icmp uge i32 %l3, 100
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br i1 %c3, label %bb4, label %exit
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bb4:
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%c4 = icmp uge i32 %l4, 100
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br i1 %c4, label %bb5, label %exit
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bb5:
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%c5 = icmp uge i32 %l4, 100
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ret i1 %c5
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exit:
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ret i1 false
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}
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;; NOTE: These prefixes are unused and the list is autogenerated. Do not add tests below this line:
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; COMMON: {{.*}}
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