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https://github.com/Gericom/teak-llvm.git
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2d858747df
This is a cleaned up version of a patch by John Regehr with permission. Originally found via the souper tool. If we add an odd number to x, then bitwise-and the result with x, we know that the low bit of the result must be zero. Either it was zero in x originally, or the add cleared it in the temporary value. As a result, one of the two values anded together must have the bit cleared. Differential Revision: http://reviews.llvm.org/D14315 llvm-svn: 252629
66 lines
1.3 KiB
LLVM
66 lines
1.3 KiB
LLVM
; RUN: opt -S -instsimplify < %s | FileCheck %s
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define i1 @test(i32 %a) {
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; CHECK-LABEL: @test
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; CHECK: ret i1 false
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%rhs = add i32 %a, -1
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%and = and i32 %a, %rhs
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%res = icmp eq i32 %and, 1
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ret i1 %res
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}
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define i1 @test2(i32 %a) {
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; CHECK-LABEL: @test2
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; CHECK: ret i1 false
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%rhs = add i32 %a, 1
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%and = and i32 %a, %rhs
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%res = icmp eq i32 %and, 1
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ret i1 %res
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}
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define i1 @test3(i32 %a) {
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; CHECK-LABEL: @test3
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; CHECK: ret i1 false
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%rhs = add i32 %a, 7
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%and = and i32 %a, %rhs
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%res = icmp eq i32 %and, 1
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ret i1 %res
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}
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@B = external global i32
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declare void @llvm.assume(i1)
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; Known bits without a constant
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define i1 @test4(i32 %a) {
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; CHECK-LABEL: @test4
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; CHECK: ret i1 false
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%b = load i32, i32* @B
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%b.and = and i32 %b, 1
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%b.cnd = icmp eq i32 %b.and, 1
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call void @llvm.assume(i1 %b.cnd)
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%rhs = add i32 %a, %b
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%and = and i32 %a, %rhs
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%res = icmp eq i32 %and, 1
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ret i1 %res
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}
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; Negative test - even number
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define i1 @test5(i32 %a) {
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; CHECK-LABEL: @test5
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; CHECK: ret i1 %res
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%rhs = add i32 %a, 2
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%and = and i32 %a, %rhs
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%res = icmp eq i32 %and, 1
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ret i1 %res
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}
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define i1 @test6(i32 %a) {
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; CHECK-LABEL: @test6
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; CHECK: ret i1 false
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%lhs = add i32 %a, -1
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%and = and i32 %lhs, %a
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%res = icmp eq i32 %and, 1
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ret i1 %res
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}
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