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2397705fe5
This fixes https://bugs.llvm.org/show_bug.cgi?id=39908. The evaluateGEPOffsetExpression() function simplifies GEP offsets for use in comparisons against zero, basically by converting X*Scale+Offset==0 to X+Offset/Scale==0 if Scale divides Offset. However, before this is done, Offset is masked down to the pointer size. This results in incorrect results for negative Offsets, because we basically end up dividing the 32-bit offset *zero* extended to 64-bit bits (rather than sign extended). Fix this by explicitly sign extending the truncated value. Differential Revision: https://reviews.llvm.org/D55449 llvm-svn: 348987
50 lines
1.7 KiB
LLVM
50 lines
1.7 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt < %s -instcombine -S | FileCheck %s
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target datalayout = "p:32:32"
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%S = type { [2 x i32] }
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define i1 @test([0 x %S]* %p, i32 %n) {
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; CHECK-LABEL: @test(
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[N:%.*]], 1
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%start.cast = bitcast [0 x %S]* %p to %S*
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%end = getelementptr inbounds [0 x %S], [0 x %S]* %p, i32 0, i32 %n, i32 0, i32 0
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%end.cast = bitcast i32* %end to %S*
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%last = getelementptr inbounds %S, %S* %end.cast, i32 -1
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%cmp = icmp eq %S* %last, %start.cast
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ret i1 %cmp
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}
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; Same test using 64-bit indices.
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define i1 @test64([0 x %S]* %p, i64 %n) {
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; CHECK-LABEL: @test64(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[N:%.*]] to i32
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP1]], 1
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%start.cast = bitcast [0 x %S]* %p to %S*
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%end = getelementptr inbounds [0 x %S], [0 x %S]* %p, i64 0, i64 %n, i32 0, i64 0
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%end.cast = bitcast i32* %end to %S*
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%last = getelementptr inbounds %S, %S* %end.cast, i64 -1
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%cmp = icmp eq %S* %last, %start.cast
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ret i1 %cmp
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}
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; Here the offset overflows and is treated modulo 2^32. This is UB.
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define i1 @test64_overflow([0 x %S]* %p, i64 %n) {
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; CHECK-LABEL: @test64_overflow(
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; CHECK-NEXT: [[TMP1:%.*]] = trunc i64 [[N:%.*]] to i32
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; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[TMP1]], 1
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; CHECK-NEXT: ret i1 [[CMP]]
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;
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%start.cast = bitcast [0 x %S]* %p to %S*
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%end = getelementptr inbounds [0 x %S], [0 x %S]* %p, i64 0, i64 %n, i32 0, i64 8589934592
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%end.cast = bitcast i32* %end to %S*
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%last = getelementptr inbounds %S, %S* %end.cast, i64 -1
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%cmp = icmp eq %S* %last, %start.cast
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ret i1 %cmp
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}
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