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[GVN] Handle not in equality propagation (#151942)

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Look through `not` when propagating equalities in GVN. Usually these
will be canonicalized away, but they may be retained due to multi-use or
involvement in logical expressions.

Fixes https://github.com/llvm/llvm-project/issues/143529.
This commit is contained in:
Nikita Popov 2025-08-05 09:11:24 +02:00 committed by GitHub
parent 8f7dfc689c
commit e044cc50ee
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GPG Key ID: B5690EEEBB952194
2 changed files with 87 additions and 0 deletions
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5
llvm/lib/Transforms/Scalar/GVN.cpp
View File

@ -2683,6 +2683,11 @@ bool GVNPass::propagateEquality(Value *LHS, Value *RHS,
Worklist.emplace_back(A, ConstantInt::get(A->getType(), IsKnownTrue));
continue;
}
if (match(LHS, m_Not(m_Value(A)))) {
Worklist.emplace_back(A, ConstantInt::get(A->getType(), !IsKnownTrue));
continue;
}
}
return Changed;

82
llvm/test/Transforms/GVN/condprop.ll
View File

@ -999,5 +999,87 @@ loop.latch:
br label %loop
}
define i1 @not_cond(i1 %c) {
; CHECK-LABEL: @not_cond(
; CHECK-NEXT: [[C_NOT:%.*]] = xor i1 [[C:%.*]], true
; CHECK-NEXT: br i1 [[C_NOT]], label [[IF:%.*]], label [[ELSE:%.*]]
; CHECK: if:
; CHECK-NEXT: ret i1 false
; CHECK: else:
; CHECK-NEXT: ret i1 true
;
%c.not = xor i1 %c, true
br i1 %c.not, label %if, label %else
if:
ret i1 %c
else:
ret i1 %c
}
define i32 @not_cond_icmp(i32 %x) {
; CHECK-LABEL: @not_cond_icmp(
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[X:%.*]], 42
; CHECK-NEXT: [[CMP_NOT:%.*]] = xor i1 [[CMP]], true
; CHECK-NEXT: br i1 [[CMP_NOT]], label [[IF:%.*]], label [[ELSE:%.*]]
; CHECK: if:
; CHECK-NEXT: ret i32 [[X]]
; CHECK: else:
; CHECK-NEXT: ret i32 42
;
%cmp = icmp eq i32 %x, 42
%cmp.not = xor i1 %cmp, true
br i1 %cmp.not, label %if, label %else
if:
ret i32 %x
else:
ret i32 %x
}
define i1 @not_cond_logic1(i1 %c, i1 %d) {
; CHECK-LABEL: @not_cond_logic1(
; CHECK-NEXT: [[C_NOT:%.*]] = xor i1 [[C:%.*]], true
; CHECK-NEXT: [[AND:%.*]] = and i1 [[C_NOT]], [[D:%.*]]
; CHECK-NEXT: br i1 [[AND]], label [[IF:%.*]], label [[ELSE:%.*]]
; CHECK: if:
; CHECK-NEXT: ret i1 false
; CHECK: else:
; CHECK-NEXT: ret i1 [[C]]
;
%c.not = xor i1 %c, true
%and = and i1 %c.not, %d
br i1 %and, label %if, label %else
if:
ret i1 %c
else:
ret i1 %c
}
define i1 @not_cond_logic2(i1 %c, i1 %d) {
; CHECK-LABEL: @not_cond_logic2(
; CHECK-NEXT: [[C_NOT:%.*]] = xor i1 [[C:%.*]], true
; CHECK-NEXT: [[AND:%.*]] = or i1 [[C_NOT]], [[D:%.*]]
; CHECK-NEXT: br i1 [[AND]], label [[IF:%.*]], label [[ELSE:%.*]]
; CHECK: if:
; CHECK-NEXT: ret i1 [[C]]
; CHECK: else:
; CHECK-NEXT: ret i1 true
;
%c.not = xor i1 %c, true
%or = or i1 %c.not, %d
br i1 %or, label %if, label %else
if:
ret i1 %c
else:
ret i1 %c
}
declare void @use_bool(i1)
declare void @use_ptr(ptr)