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[InstCombine] Extend Phi-Icmp use to include or #67682

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Merged
merged 7 commits into from
Oct 24, 2023
Merged

[InstCombine] Extend Phi-Icmp use to include or #67682

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ec137d7
Extend PhiIcmp use to include or
bipmis Sep 28, 2023
2255544
Address Review Comments and add icmp ne tests
bipmis Oct 2, 2023
0a37a28
Update the comments on phi uses as per review
bipmis Oct 5, 2023
8fdd84e
Update to use hasNUsesOrMore
bipmis Oct 5, 2023
1c16f26
Revert to the branch base to precommit tests
bipmis Oct 9, 2023
612771d
Precommit tests for extending phi-icmp use to include or
bipmis Oct 9, 2023
0ec3ab8
Make all changes including review comments
bipmis Oct 9, 2023
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44 changes: 31 additions & 13 deletions llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1441,18 +1441,37 @@ Instruction *InstCombinerImpl::visitPHINode(PHINode &PN) {
PHIUser->user_back() == &PN) {
return replaceInstUsesWith(PN, PoisonValue::get(PN.getType()));
}
// When a PHI is used only to be compared with zero, it is safe to replace
// an incoming value proved as known nonzero with any non-zero constant.
// For example, in the code below, the incoming value %v can be replaced
// with any non-zero constant based on the fact that the PHI is only used to
// be compared with zero and %v is a known non-zero value:
// %v = select %cond, 1, 2
// %p = phi [%v, BB] ...
// icmp eq, %p, 0
auto *CmpInst = dyn_cast<ICmpInst>(PHIUser);
// FIXME: To be simple, handle only integer type for now.
if (CmpInst && isa<IntegerType>(PN.getType()) && CmpInst->isEquality() &&
match(CmpInst->getOperand(1), m_Zero())) {
}

// When a PHI is used only to be compared with zero, it is safe to replace
// an incoming value proved as known nonzero with any non-zero constant.
// For example, in the code below, the incoming value %v can be replaced
// with any non-zero constant based on the fact that the PHI is only used to
// be compared with zero and %v is a known non-zero value:
// %v = select %cond, 1, 2
// %p = phi [%v, BB] ...
// icmp eq, %p, 0
// FIXME: To be simple, handle only integer type for now.
// This handles a small number of uses to keep the complexity down, and an
// icmp(or(phi)) can equally be replaced with any non-zero constant as the
// "or" will only add bits.
if (!PN.hasNUsesOrMore(3)) {
bool AllUsesOfPhiEndsInCmp = all_of(PN.users(), [&PN](User *U) {
auto *CmpInst = dyn_cast<ICmpInst>(U);
if (!CmpInst) {
// This is always correct as OR only add bits and we are checking
// against 0.
if (U->hasOneUse() && match(U, m_c_Or(m_Specific(&PN), m_Value())))
CmpInst = dyn_cast<ICmpInst>(U->user_back());
}
if (!CmpInst || !isa<IntegerType>(PN.getType()) ||
!CmpInst->isEquality() || !match(CmpInst->getOperand(1), m_Zero())) {
return false;
}
return true;
});
// All uses of PHI results in a compare with zero.
if (AllUsesOfPhiEndsInCmp) {
ConstantInt *NonZeroConst = nullptr;
bool MadeChange = false;
for (unsigned I = 0, E = PN.getNumIncomingValues(); I != E; ++I) {
Expand All @@ -1461,7 +1480,6 @@ Instruction *InstCombinerImpl::visitPHINode(PHINode &PN) {
if (isKnownNonZero(VA, DL, 0, &AC, CtxI, &DT)) {
if (!NonZeroConst)
NonZeroConst = getAnyNonZeroConstInt(PN);

if (NonZeroConst != VA) {
replaceOperand(PN, I, NonZeroConst);
MadeChange = true;
Expand Down
302 changes: 302 additions & 0 deletions llvm/test/Transforms/InstCombine/phi.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -1286,6 +1286,308 @@ if.end: ; preds = %entry, %if.then
ret i1 %cmp1
}

define i1 @phi_knownnonzero_eq_oricmp(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_eq_oricmp(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ 1, [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ORPHI:%.*]] = or i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[ORPHI]], 0
; CHECK-NEXT: ret i1 [[CMP1]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%orphi = or i32 %phi, %val
%cmp1 = icmp eq i32 %orphi, 0
ret i1 %cmp1
}

define i1 @phi_knownnonzero_eq_oricmp_commuted(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_eq_oricmp_commuted(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ 1, [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ORPHI:%.*]] = or i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[ORPHI]], 0
; CHECK-NEXT: ret i1 [[CMP1]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%orphi = or i32 %val, %phi
%cmp1 = icmp eq i32 %orphi, 0
ret i1 %cmp1
}

define i1 @phi_knownnonzero_ne_oricmp(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_ne_oricmp(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ 1, [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ORPHI:%.*]] = or i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[ORPHI]], 0
; CHECK-NEXT: ret i1 [[CMP1]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%orphi = or i32 %phi, %val
%cmp1 = icmp ne i32 %orphi, 0
ret i1 %cmp1
}

define i1 @phi_knownnonzero_ne_oricmp_commuted(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_ne_oricmp_commuted(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ 1, [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ORPHI:%.*]] = or i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[ORPHI]], 0
; CHECK-NEXT: ret i1 [[CMP1]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%orphi = or i32 %val, %phi
%cmp1 = icmp ne i32 %orphi, 0
ret i1 %cmp1
}

define i1 @phi_knownnonzero_eq_multiuse_oricmp(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_eq_multiuse_oricmp(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ 1, [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ORPHI:%.*]] = or i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[ORPHI]], 0
; CHECK-NEXT: br i1 [[CMP1]], label [[NEXT:%.*]], label [[CLEANUP:%.*]]
; CHECK: next:
; CHECK-NEXT: [[BOOL2:%.*]] = icmp eq i32 [[PHI]], 0
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[FINAL:%.*]] = phi i1 [ [[CMP1]], [[IF_END]] ], [ [[BOOL2]], [[NEXT]] ]
; CHECK-NEXT: ret i1 [[FINAL]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%orphi = or i32 %phi, %val
%cmp1 = icmp eq i32 %orphi, 0
br i1 %cmp1, label %next, label %cleanup

next:
%bool2 = icmp eq i32 %phi, 0
br label %cleanup

cleanup:
%final = phi i1 [ %cmp1, %if.end ], [ %bool2, %next ]
ret i1 %final
}

define i1 @phi_knownnonzero_ne_multiuse_oricmp_commuted(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_ne_multiuse_oricmp_commuted(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ 1, [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ORPHI:%.*]] = or i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[ORPHI]], 0
; CHECK-NEXT: br i1 [[CMP1]], label [[NEXT:%.*]], label [[CLEANUP:%.*]]
; CHECK: next:
; CHECK-NEXT: [[BOOL2:%.*]] = icmp ne i32 [[PHI]], 0
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[FINAL:%.*]] = phi i1 [ [[CMP1]], [[IF_END]] ], [ [[BOOL2]], [[NEXT]] ]
; CHECK-NEXT: ret i1 [[FINAL]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%orphi = or i32 %val, %phi
%cmp1 = icmp ne i32 %orphi, 0
br i1 %cmp1, label %next, label %cleanup

next:
%bool2 = icmp ne i32 %phi, 0
br label %cleanup

cleanup:
%final = phi i1 [ %cmp1, %if.end ], [ %bool2, %next ]
ret i1 %final
}

define i1 @phi_knownnonzero_eq_multiuse_andicmp(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_eq_multiuse_andicmp(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[LOAD:%.*]] = load i32, ptr [[P:%.*]], align 4
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[LOAD]], [[N]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i32 1, i32 2
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ [[SEL]], [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ANDPHI:%.*]] = and i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp eq i32 [[ANDPHI]], 0
; CHECK-NEXT: br i1 [[CMP1]], label [[NEXT:%.*]], label [[CLEANUP:%.*]]
; CHECK: next:
; CHECK-NEXT: [[BOOL2:%.*]] = icmp eq i32 [[PHI]], 0
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[FINAL:%.*]] = phi i1 [ [[CMP1]], [[IF_END]] ], [ [[BOOL2]], [[NEXT]] ]
; CHECK-NEXT: ret i1 [[FINAL]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%andphi = and i32 %phi, %val
%cmp1 = icmp eq i32 %andphi, 0
br i1 %cmp1, label %next, label %cleanup

next:
%bool2 = icmp eq i32 %phi, 0
br label %cleanup

cleanup:
%final = phi i1 [ %cmp1, %if.end ], [ %bool2, %next ]
ret i1 %final
}

define i1 @phi_knownnonzero_ne_multiuse_andicmp(i32 %n, i32 %s, ptr %P, i32 %val) {
; CHECK-LABEL: @phi_knownnonzero_ne_multiuse_andicmp(
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TOBOOL:%.*]] = icmp slt i32 [[N:%.*]], [[S:%.*]]
; CHECK-NEXT: br i1 [[TOBOOL]], label [[IF_END:%.*]], label [[IF_THEN:%.*]]
; CHECK: if.then:
; CHECK-NEXT: [[LOAD:%.*]] = load i32, ptr [[P:%.*]], align 4
; CHECK-NEXT: [[CMP:%.*]] = icmp eq i32 [[LOAD]], [[N]]
; CHECK-NEXT: [[SEL:%.*]] = select i1 [[CMP]], i32 1, i32 2
; CHECK-NEXT: br label [[IF_END]]
; CHECK: if.end:
; CHECK-NEXT: [[PHI:%.*]] = phi i32 [ [[SEL]], [[IF_THEN]] ], [ [[N]], [[ENTRY:%.*]] ]
; CHECK-NEXT: [[ANDPHI:%.*]] = and i32 [[PHI]], [[VAL:%.*]]
; CHECK-NEXT: [[CMP1:%.*]] = icmp ne i32 [[ANDPHI]], 0
; CHECK-NEXT: br i1 [[CMP1]], label [[NEXT:%.*]], label [[CLEANUP:%.*]]
; CHECK: next:
; CHECK-NEXT: [[BOOL2:%.*]] = icmp ne i32 [[PHI]], 0
; CHECK-NEXT: br label [[CLEANUP]]
; CHECK: cleanup:
; CHECK-NEXT: [[FINAL:%.*]] = phi i1 [ [[CMP1]], [[IF_END]] ], [ [[BOOL2]], [[NEXT]] ]
; CHECK-NEXT: ret i1 [[FINAL]]
;
entry:
%tobool = icmp slt i32 %n, %s
br i1 %tobool, label %if.end, label %if.then

if.then:
%load = load i32, ptr %P
%cmp = icmp eq i32 %n, %load
%sel = select i1 %cmp, i32 1, i32 2
br label %if.end

if.end:
%phi = phi i32 [ %sel, %if.then ], [ %n, %entry ]
%andphi = and i32 %phi, %val
%cmp1 = icmp ne i32 %andphi, 0
br i1 %cmp1, label %next, label %cleanup

next:
%bool2 = icmp ne i32 %phi, 0
br label %cleanup

cleanup:
%final = phi i1 [ %cmp1, %if.end ], [ %bool2, %next ]
ret i1 %final
}

; This would crash trying to delete an instruction (conv)
; that still had uses because the user (the phi) was not
; updated to remove a use from an unreachable block (g.exit).
Expand Down