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llvm-project/llvm/test/Transforms/InstCombine/ctpop.ll

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[InstCombine] Use update_test_checks to regenerate the ctpop test. NFC llvm-svn: 303659
2017-05-24 01:20:18 +08:00
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
Tighten known bits for ctpop based on zero input bits This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer. The basic idea here is that input bits that are known zero reduce the maximum count that the intrinsic could return. We know that the number of bits required to represent a particular count is at most log2(N)+1. Differential Revision: http://reviews.llvm.org/D13253 llvm-svn: 250338
2015-10-15 06:42:12 +08:00
; RUN: opt < %s -S -instcombine | FileCheck %s
declare i32 @llvm.ctpop.i32(i32)
declare i8 @llvm.ctpop.i8(i8)
declare void @llvm.assume(i1)
define i1 @test1(i32 %arg) {
[InstCombine] Use update_test_checks to regenerate the ctpop test. NFC llvm-svn: 303659
2017-05-24 01:20:18 +08:00
; CHECK-LABEL: @test1(
; CHECK-NEXT: ret i1 false
;
Tighten known bits for ctpop based on zero input bits This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer. The basic idea here is that input bits that are known zero reduce the maximum count that the intrinsic could return. We know that the number of bits required to represent a particular count is at most log2(N)+1. Differential Revision: http://reviews.llvm.org/D13253 llvm-svn: 250338
2015-10-15 06:42:12 +08:00
%and = and i32 %arg, 15
%cnt = call i32 @llvm.ctpop.i32(i32 %and)
%res = icmp eq i32 %cnt, 9
ret i1 %res
}
define i1 @test2(i32 %arg) {
[InstCombine] Use update_test_checks to regenerate the ctpop test. NFC llvm-svn: 303659
2017-05-24 01:20:18 +08:00
; CHECK-LABEL: @test2(
; CHECK-NEXT: ret i1 false
;
Tighten known bits for ctpop based on zero input bits This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer. The basic idea here is that input bits that are known zero reduce the maximum count that the intrinsic could return. We know that the number of bits required to represent a particular count is at most log2(N)+1. Differential Revision: http://reviews.llvm.org/D13253 llvm-svn: 250338
2015-10-15 06:42:12 +08:00
%and = and i32 %arg, 1
%cnt = call i32 @llvm.ctpop.i32(i32 %and)
%res = icmp eq i32 %cnt, 2
ret i1 %res
}
define i1 @test3(i32 %arg) {
[InstCombine] Use update_test_checks to regenerate the ctpop test. NFC llvm-svn: 303659
2017-05-24 01:20:18 +08:00
; CHECK-LABEL: @test3(
; CHECK-NEXT: [[ASSUME:%.*]] = icmp eq i32 [[ARG:%.*]], 0
; CHECK-NEXT: call void @llvm.assume(i1 [[ASSUME]])
; CHECK-NEXT: ret i1 false
;
;; Use an assume to make all the bits known without triggering constant
Tighten known bits for ctpop based on zero input bits This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer. The basic idea here is that input bits that are known zero reduce the maximum count that the intrinsic could return. We know that the number of bits required to represent a particular count is at most log2(N)+1. Differential Revision: http://reviews.llvm.org/D13253 llvm-svn: 250338
2015-10-15 06:42:12 +08:00
;; folding. This is trying to hit a corner case where we have to avoid
;; taking the log of 0.
%assume = icmp eq i32 %arg, 0
call void @llvm.assume(i1 %assume)
%cnt = call i32 @llvm.ctpop.i32(i32 %arg)
%res = icmp eq i32 %cnt, 2
ret i1 %res
}
; Negative test for when we know nothing
define i1 @test4(i8 %arg) {
[InstCombine] Use update_test_checks to regenerate the ctpop test. NFC llvm-svn: 303659
2017-05-24 01:20:18 +08:00
; CHECK-LABEL: @test4(
; CHECK-NEXT: [[CNT:%.*]] = call i8 @llvm.ctpop.i8(i8 [[ARG:%.*]])
; CHECK-NEXT: [[RES:%.*]] = icmp eq i8 [[CNT]], 2
; CHECK-NEXT: ret i1 [[RES]]
;
Tighten known bits for ctpop based on zero input bits This is a cleaned up patch from the one written by John Regehr based on the findings of the Souper superoptimizer. The basic idea here is that input bits that are known zero reduce the maximum count that the intrinsic could return. We know that the number of bits required to represent a particular count is at most log2(N)+1. Differential Revision: http://reviews.llvm.org/D13253 llvm-svn: 250338
2015-10-15 06:42:12 +08:00
%cnt = call i8 @llvm.ctpop.i8(i8 %arg)
%res = icmp eq i8 %cnt, 2
ret i1 %res
}
[InstCombine] Add test cases to show missed opportunities to remove compare instructions after cttz/ctlz/ctpop where some bits of the input is known. llvm-svn: 304224
2017-05-31 01:47:59 +08:00
; Test when the number of possible known bits isn't one less than a power of 2
; and the compare value is greater but less than the next power of 2.
; TODO: The icmp is unnecessary given the known bits of the input.
define i1 @test5(i32 %arg) {
; CHECK-LABEL: @test5(
; CHECK-NEXT: [[AND:%.*]] = and i32 [[ARG:%.*]], 3
; CHECK-NEXT: [[CNT:%.*]] = call i32 @llvm.ctpop.i32(i32 [[AND]])
; CHECK-NEXT: [[RES:%.*]] = icmp eq i32 [[CNT]], 3
; CHECK-NEXT: ret i1 [[RES]]
;
%and = and i32 %arg, 3
%cnt = call i32 @llvm.ctpop.i32(i32 %and)
%res = icmp eq i32 %cnt, 3
ret i1 %res
}