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llvm-project/llvm/test/Transforms/InstCombine/conditional-negation.ll
Nikita Popov a105877646
[InstCombine] Remove some of the complexity-based canonicalization (#91185) 
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.
2024-08-21 12:02:54 +02:00

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; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt < %s -passes=instcombine -S | FileCheck %s
; Basic pattern
define i8 @t0(i8 %x, i1 %cond) {
; CHECK-LABEL: @t0(
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND:%.*]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat = sext i1 %cond to i8
%sub = add i8 %cond.splat, %x
%xor = xor i8 %sub, %cond.splat
ret i8 %xor
}
define <2 x i8> @t0_vec(<2 x i8> %x, <2 x i1> %cond) {
; CHECK-LABEL: @t0_vec(
; CHECK-NEXT: [[X_NEG:%.*]] = sub <2 x i8> zeroinitializer, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select <2 x i1> [[COND:%.*]], <2 x i8> [[X_NEG]], <2 x i8> [[X]]
; CHECK-NEXT: ret <2 x i8> [[XOR]]
;
%cond.splat = sext <2 x i1> %cond to <2 x i8>
%sub = add <2 x i8> %cond.splat, %x
%xor = xor <2 x i8> %sub, %cond.splat
ret <2 x i8> %xor
}
; Two different extensions are fine
define i8 @t1(i8 %x, i1 %cond) {
; CHECK-LABEL: @t1(
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND:%.*]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
%cond.splat1 = sext i1 %cond to i8
%sub = add i8 %cond.splat0, %x
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
; Two different extensions of different conditions are not fine
define i8 @t2(i8 %x, i1 %cond0, i1 %cond1) {
; CHECK-LABEL: @t2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND0:%.*]] to i8
; CHECK-NEXT: [[COND_SPLAT1:%.*]] = sext i1 [[COND1:%.*]] to i8
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT0]]
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[SUB]], [[COND_SPLAT1]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond0 to i8
%cond.splat1 = sext i1 %cond1 to i8
%sub = add i8 %cond.splat0, %x
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
; Condition must be boolean.
define i8 @t3(i8 %x, i2 %cond) {
; CHECK-LABEL: @t3(
; CHECK-NEXT: [[COND_SPLAT:%.*]] = sext i2 [[COND:%.*]] to i8
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT]]
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[SUB]], [[COND_SPLAT]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat = sext i2 %cond to i8
%sub = add i8 %cond.splat, %x
%xor = xor i8 %sub, %cond.splat
ret i8 %xor
}
define <2 x i8> @t3_vec(<2 x i8> %x, <2 x i2> %cond) {
; CHECK-LABEL: @t3_vec(
; CHECK-NEXT: [[COND_SPLAT:%.*]] = sext <2 x i2> [[COND:%.*]] to <2 x i8>
; CHECK-NEXT: [[SUB:%.*]] = add <2 x i8> [[X:%.*]], [[COND_SPLAT]]
; CHECK-NEXT: [[XOR:%.*]] = xor <2 x i8> [[SUB]], [[COND_SPLAT]]
; CHECK-NEXT: ret <2 x i8> [[XOR]]
;
%cond.splat = sext <2 x i2> %cond to <2 x i8>
%sub = add <2 x i8> %cond.splat, %x
%xor = xor <2 x i8> %sub, %cond.splat
ret <2 x i8> %xor
}
; add is commutative
; xor is not commutative here because of complexity ordering
define i8 @xor.commuted(i1 %cond) {
; CHECK-LABEL: @xor.commuted(
; CHECK-NEXT: [[X:%.*]] = call i8 @gen.i8()
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND:%.*]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat = sext i1 %cond to i8
%x = call i8 @gen.i8()
%sub = add i8 %x, %cond.splat
%xor = xor i8 %sub, %cond.splat
ret i8 %xor
}
; Extra use tests
define i8 @extrause01_v1(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause01_v1(
; CHECK-NEXT: [[COND_SPLAT:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT]])
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat)
%sub = add i8 %cond.splat, %x
%xor = xor i8 %sub, %cond.splat
ret i8 %xor
}
define i8 @extrause10_v1(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause10_v1(
; CHECK-NEXT: [[COND_SPLAT:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT]]
; CHECK-NEXT: call void @use.i8(i8 [[SUB]])
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[SUB]], [[COND_SPLAT]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat = sext i1 %cond to i8
%sub = add i8 %cond.splat, %x
call void @use.i8(i8 %sub)
%xor = xor i8 %sub, %cond.splat
ret i8 %xor
}
define i8 @extrause11_v1(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause11_v1(
; CHECK-NEXT: [[COND_SPLAT:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT]])
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT]]
; CHECK-NEXT: call void @use.i8(i8 [[SUB]])
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[SUB]], [[COND_SPLAT]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat)
%sub = add i8 %cond.splat, %x
call void @use.i8(i8 %sub)
%xor = xor i8 %sub, %cond.splat
ret i8 %xor
}
; Extra use tests with two extensions
define i8 @extrause001_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause001_v2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT0]])
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat0)
%cond.splat1 = sext i1 %cond to i8
%sub = add i8 %cond.splat0, %x
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
define i8 @extrause010_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause010_v2(
; CHECK-NEXT: [[COND_SPLAT1:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT1]])
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
%cond.splat1 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat1)
%sub = add i8 %cond.splat0, %x
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
define i8 @extrause011_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause011_v2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT0]])
; CHECK-NEXT: [[COND_SPLAT1:%.*]] = sext i1 [[COND]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT1]])
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X:%.*]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat0)
%cond.splat1 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat1)
%sub = add i8 %cond.splat0, %x
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
define i8 @extrause100_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause100_v2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT0]]
; CHECK-NEXT: call void @use.i8(i8 [[SUB]])
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
%cond.splat1 = sext i1 %cond to i8
%sub = add i8 %cond.splat0, %x
call void @use.i8(i8 %sub)
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
define i8 @extrause101_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause101_v2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT0]])
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT0]]
; CHECK-NEXT: call void @use.i8(i8 [[SUB]])
; CHECK-NEXT: [[X_NEG:%.*]] = sub i8 0, [[X]]
; CHECK-NEXT: [[XOR:%.*]] = select i1 [[COND]], i8 [[X_NEG]], i8 [[X]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat0)
%cond.splat1 = sext i1 %cond to i8
%sub = add i8 %cond.splat0, %x
call void @use.i8(i8 %sub)
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
define i8 @extrause110_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause110_v2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: [[COND_SPLAT1:%.*]] = sext i1 [[COND]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT1]])
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT0]]
; CHECK-NEXT: call void @use.i8(i8 [[SUB]])
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[SUB]], [[COND_SPLAT1]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
%cond.splat1 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat1)
%sub = add i8 %cond.splat0, %x
call void @use.i8(i8 %sub)
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
define i8 @extrause111_v2(i8 %x, i1 %cond) {
; CHECK-LABEL: @extrause111_v2(
; CHECK-NEXT: [[COND_SPLAT0:%.*]] = sext i1 [[COND:%.*]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT0]])
; CHECK-NEXT: [[COND_SPLAT1:%.*]] = sext i1 [[COND]] to i8
; CHECK-NEXT: call void @use.i8(i8 [[COND_SPLAT1]])
; CHECK-NEXT: [[SUB:%.*]] = add i8 [[X:%.*]], [[COND_SPLAT0]]
; CHECK-NEXT: call void @use.i8(i8 [[SUB]])
; CHECK-NEXT: [[XOR:%.*]] = xor i8 [[SUB]], [[COND_SPLAT1]]
; CHECK-NEXT: ret i8 [[XOR]]
;
%cond.splat0 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat0)
%cond.splat1 = sext i1 %cond to i8
call void @use.i8(i8 %cond.splat1)
%sub = add i8 %cond.splat0, %x
call void @use.i8(i8 %sub)
%xor = xor i8 %sub, %cond.splat1
ret i8 %xor
}
declare void @use.i8(i8)
declare i8 @gen.i8()
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