a105877646
The idea behind this canonicalization is that it allows us to handle less patterns, because we know that some will be canonicalized away. This is indeed very useful to e.g. know that constants are always on the right. However, this is only useful if the canonicalization is actually reliable. This is the case for constants, but not for arguments: Moving these to the right makes it look like the "more complex" expression is guaranteed to be on the left, but this is not actually the case in practice. It fails as soon as you replace the argument with another instruction. The end result is that it looks like things correctly work in tests, while they actually don't. We use the "thwart complexity-based canonicalization" trick to handle this in tests, but it's often a challenge for new contributors to get this right, and based on the regressions this PR originally exposed, we clearly don't get this right in many cases. For this reason, I think that it's better to remove this complexity canonicalization. It will make it much easier to write tests for commuted cases and make sure that they are handled.
65 lines
1.8 KiB
LLVM
65 lines
1.8 KiB
LLVM
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
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; RUN: opt < %s -passes=instcombine -S | FileCheck %s
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; These tests are for Integer BitWidth <= 64 && BitWidth % 2 != 0.
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;; A | ~A == -1
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define i23 @test1(i23 %A) {
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; CHECK-LABEL: define i23 @test1(
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; CHECK-SAME: i23 [[A:%.*]]) {
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; CHECK-NEXT: ret i23 -1
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;
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%NotA = xor i23 -1, %A
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%B = or i23 %A, %NotA
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ret i23 %B
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}
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;; If we have: ((V + N) & C1) | (V & C2)
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;; .. and C2 = ~C1 and C2 is 0+1+ and (N & C2) == 0
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;; replace with V+N.
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define i39 @test2(i39 %V, i39 %M) {
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; CHECK-LABEL: define i39 @test2(
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; CHECK-SAME: i39 [[V:%.*]], i39 [[M:%.*]]) {
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; CHECK-NEXT: [[N:%.*]] = and i39 [[M]], -274877906944
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; CHECK-NEXT: [[A:%.*]] = add i39 [[V]], [[N]]
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; CHECK-NEXT: ret i39 [[A]]
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;
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%C1 = xor i39 274877906943, -1 ;; C2 = 274877906943
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%N = and i39 %M, 274877906944
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%A = add i39 %V, %N
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%B = and i39 %A, %C1
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%D = and i39 %V, 274877906943
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%R = or i39 %B, %D
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ret i39 %R
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}
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; These tests are for Integer BitWidth > 64 && BitWidth <= 1024.
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;; A | ~A == -1
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define i1023 @test4(i1023 %A) {
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; CHECK-LABEL: define i1023 @test4(
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; CHECK-SAME: i1023 [[A:%.*]]) {
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; CHECK-NEXT: ret i1023 -1
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;
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%NotA = xor i1023 -1, %A
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%B = or i1023 %A, %NotA
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ret i1023 %B
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}
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;; If we have: ((V + N) & C1) | (V & C2)
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;; .. and C2 = ~C1 and C2 is 0+1+ and (N & C2) == 0
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;; replace with V+N.
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define i399 @test5(i399 %V, i399 %M) {
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; CHECK-LABEL: define i399 @test5(
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; CHECK-SAME: i399 [[V:%.*]], i399 [[M:%.*]]) {
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; CHECK-NEXT: [[N:%.*]] = and i399 [[M]], 18446742974197923840
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; CHECK-NEXT: [[A:%.*]] = add i399 [[V]], [[N]]
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; CHECK-NEXT: ret i399 [[A]]
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;
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%C1 = xor i399 274877906943, -1 ;; C2 = 274877906943
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%N = and i399 %M, 18446742974197923840
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%A = add i399 %V, %N
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%B = and i399 %A, %C1
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%D = and i399 %V, 274877906943
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%R = or i399 %B, %D
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ret i399 %R
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}
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