887865c1ad
Fixes bug 40992: https://bugs.llvm.org/show_bug.cgi?id=40992 There is potential for miscompiled code emitted from JumpThreading when analyzing a block with one or more indirectbr or callbr predecessors. The ProcessThreadableEdges() function incorrectly folds conditional branches into an unconditional branch. This patch prevents incorrect branch folding without fully pessimizing other potential threading opportunities through the same basic block. This IR shape was manually fed in via opt and is unclear if clang and the full pass pipeline will ever emit similar code shapes. Thanks to Matthias Liedtke for the bug report and simplified IR example. Differential Revision: https://reviews.llvm.org/D60284 llvm-svn: 357930
45 lines
849 B
LLVM
45 lines
849 B
LLVM
; RUN: opt -S < %s -jump-threading | FileCheck %s
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; PR40992: Do not incorrectly fold %bb5 into an unconditional br to %bb7.
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; Also verify we correctly thread %bb1 -> %bb7 when %c is false.
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define i32 @jtbr(i1 %v1, i1 %v2, i1 %v3) {
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; CHECK: bb0:
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bb0:
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br label %bb1
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; CHECK: bb1:
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; CHECK-NEXT: and
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; CHECK-NEXT: br i1 %c, label %bb2, label %bb7
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bb1:
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%c = and i1 %v1, %v2
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br i1 %c, label %bb2, label %bb5
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; CHECK: bb2:
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; CHECK-NEXT: select
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; CHECK-NEXT: indirectbr i8* %ba, [label %bb3, label %bb5]
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bb2:
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%ba = select i1 %v3, i8* blockaddress(@jtbr, %bb3), i8* blockaddress(@jtbr, %bb4)
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indirectbr i8* %ba, [label %bb3, label %bb4]
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; CHECK: bb3:
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bb3:
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br label %bb1
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; CHECK-NOT: bb4:
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bb4:
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br label %bb5
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; CHECK: bb5:
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bb5:
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br i1 %c, label %bb6, label %bb7
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; CHECK: bb6:
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bb6:
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ret i32 0
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; CHECK: bb7:
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bb7:
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ret i32 1
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}
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