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[ConstraintElimination] Add support for UCMP/SCMP intrinsics (#97974)
This adds checks to fold calls to `ucmp`/`scmp` where a comparative relationship between the arguments can be established.
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2 files changed

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‎llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1087,6 +1087,8 @@ void State::addInfoFor(BasicBlock &BB) {
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}
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// Enqueue ssub_with_overflow for simplification.
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case Intrinsic::ssub_with_overflow:
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case Intrinsic::ucmp:
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case Intrinsic::scmp:
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WorkList.push_back(
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FactOrCheck::getCheck(DT.getNode(&BB), cast<CallInst>(&I)));
10921094
break;
@@ -1448,6 +1450,28 @@ static bool checkAndReplaceMinMax(MinMaxIntrinsic *MinMax, ConstraintInfo &Info,
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return false;
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}
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static bool checkAndReplaceCmp(CmpIntrinsic *I, ConstraintInfo &Info,
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SmallVectorImpl<Instruction *> &ToRemove) {
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Value *LHS = I->getOperand(0);
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Value *RHS = I->getOperand(1);
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if (checkCondition(I->getGTPredicate(), LHS, RHS, I, Info).value_or(false)) {
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I->replaceAllUsesWith(ConstantInt::get(I->getType(), 1));
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ToRemove.push_back(I);
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return true;
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}
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if (checkCondition(I->getLTPredicate(), LHS, RHS, I, Info).value_or(false)) {
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I->replaceAllUsesWith(ConstantInt::getSigned(I->getType(), -1));
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ToRemove.push_back(I);
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return true;
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}
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if (checkCondition(ICmpInst::ICMP_EQ, LHS, RHS, I, Info)) {
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I->replaceAllUsesWith(ConstantInt::get(I->getType(), 0));
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ToRemove.push_back(I);
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return true;
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}
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return false;
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}
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static void
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removeEntryFromStack(const StackEntry &E, ConstraintInfo &Info,
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Module *ReproducerModule,
@@ -1750,6 +1774,8 @@ static bool eliminateConstraints(Function &F, DominatorTree &DT, LoopInfo &LI,
17501774
Changed |= Simplified;
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} else if (auto *MinMax = dyn_cast<MinMaxIntrinsic>(Inst)) {
17521776
Changed |= checkAndReplaceMinMax(MinMax, Info, ToRemove);
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} else if (auto *CmpIntr = dyn_cast<CmpIntrinsic>(Inst)) {
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Changed |= checkAndReplaceCmp(CmpIntr, Info, ToRemove);
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}
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continue;
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}

‎llvm/test/Transforms/ConstraintElimination/uscmp.ll

Lines changed: 149 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,149 @@
1+
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
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; RUN: opt -passes=constraint-elimination -S %s | FileCheck %s
3+
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define i8 @scmp_1(i32 %x, i32 %y) {
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; CHECK-LABEL: @scmp_1(
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; CHECK-NEXT: [[COND:%.*]] = icmp sgt i32 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
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; CHECK: true:
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; CHECK-NEXT: ret i8 1
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; CHECK: false:
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; CHECK-NEXT: ret i8 20
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;
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%cond = icmp sgt i32 %x, %y
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br i1 %cond, label %true, label %false
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true:
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%r = call i8 @llvm.scmp(i32 %x, i32 %y)
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ret i8 %r
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false:
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ret i8 20
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}
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define i8 @ucmp_1(i32 %x, i32 %y) {
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; CHECK-LABEL: @ucmp_1(
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; CHECK-NEXT: [[COND:%.*]] = icmp ult i32 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
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; CHECK: true:
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; CHECK-NEXT: ret i8 -1
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; CHECK: false:
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; CHECK-NEXT: ret i8 20
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;
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%cond = icmp ult i32 %x, %y
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br i1 %cond, label %true, label %false
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true:
34+
%r = call i8 @llvm.ucmp(i32 %x, i32 %y)
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ret i8 %r
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false:
37+
ret i8 20
38+
}
39+
40+
define i8 @scmp_2(i32 %x, i32 %y) {
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; CHECK-LABEL: @scmp_2(
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; CHECK-NEXT: [[COND:%.*]] = icmp sge i32 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
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; CHECK: true:
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; CHECK-NEXT: ret i8 20
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; CHECK: false:
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; CHECK-NEXT: ret i8 -1
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;
49+
%cond = icmp sge i32 %x, %y
50+
br i1 %cond, label %true, label %false
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true:
52+
ret i8 20
53+
false:
54+
%r = call i8 @llvm.scmp(i32 %x, i32 %y)
55+
ret i8 %r
56+
}
57+
58+
define i8 @ucmp_2(i32 %x, i32 %y) {
59+
; CHECK-LABEL: @ucmp_2(
60+
; CHECK-NEXT: [[COND:%.*]] = icmp ule i32 [[X:%.*]], [[Y:%.*]]
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; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
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; CHECK: true:
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; CHECK-NEXT: ret i8 20
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; CHECK: false:
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; CHECK-NEXT: ret i8 1
66+
;
67+
%cond = icmp ule i32 %x, %y
68+
br i1 %cond, label %true, label %false
69+
true:
70+
ret i8 20
71+
false:
72+
%r = call i8 @llvm.ucmp(i32 %x, i32 %y)
73+
ret i8 %r
74+
}
75+
76+
define i8 @scmp_3(i32 %x, i32 %y) {
77+
; CHECK-LABEL: @scmp_3(
78+
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[X:%.*]], [[Y:%.*]]
79+
; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
80+
; CHECK: true:
81+
; CHECK-NEXT: ret i8 0
82+
; CHECK: false:
83+
; CHECK-NEXT: ret i8 20
84+
;
85+
%cond = icmp eq i32 %x, %y
86+
br i1 %cond, label %true, label %false
87+
true:
88+
%r = call i8 @llvm.scmp(i32 %x, i32 %y)
89+
ret i8 %r
90+
false:
91+
ret i8 20
92+
}
93+
94+
define i8 @ucmp_3(i32 %x, i32 %y) {
95+
; CHECK-LABEL: @ucmp_3(
96+
; CHECK-NEXT: [[COND:%.*]] = icmp eq i32 [[X:%.*]], [[Y:%.*]]
97+
; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
98+
; CHECK: true:
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; CHECK-NEXT: ret i8 0
100+
; CHECK: false:
101+
; CHECK-NEXT: ret i8 20
102+
;
103+
%cond = icmp eq i32 %x, %y
104+
br i1 %cond, label %true, label %false
105+
true:
106+
%r = call i8 @llvm.ucmp(i32 %x, i32 %y)
107+
ret i8 %r
108+
false:
109+
ret i8 20
110+
}
111+
112+
; Negative test: signedness mismatch
113+
define i8 @scmp_4(i32 %x, i32 %y) {
114+
; CHECK-LABEL: @scmp_4(
115+
; CHECK-NEXT: [[COND:%.*]] = icmp ugt i32 [[X:%.*]], [[Y:%.*]]
116+
; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
117+
; CHECK: true:
118+
; CHECK-NEXT: ret i8 20
119+
; CHECK: false:
120+
; CHECK-NEXT: [[R:%.*]] = call i8 @llvm.scmp.i8.i32(i32 [[X]], i32 [[Y]])
121+
; CHECK-NEXT: ret i8 [[R]]
122+
;
123+
%cond = icmp ugt i32 %x, %y
124+
br i1 %cond, label %true, label %false
125+
true:
126+
ret i8 20
127+
false:
128+
%r = call i8 @llvm.scmp(i32 %x, i32 %y)
129+
ret i8 %r
130+
}
131+
132+
define i8 @ucmp_4(i32 %x, i32 %y) {
133+
; CHECK-LABEL: @ucmp_4(
134+
; CHECK-NEXT: [[COND:%.*]] = icmp slt i32 [[X:%.*]], [[Y:%.*]]
135+
; CHECK-NEXT: br i1 [[COND]], label [[TRUE:%.*]], label [[FALSE:%.*]]
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; CHECK: true:
137+
; CHECK-NEXT: ret i8 20
138+
; CHECK: false:
139+
; CHECK-NEXT: [[R:%.*]] = call i8 @llvm.ucmp.i8.i32(i32 [[X]], i32 [[Y]])
140+
; CHECK-NEXT: ret i8 [[R]]
141+
;
142+
%cond = icmp slt i32 %x, %y
143+
br i1 %cond, label %true, label %false
144+
true:
145+
ret i8 20
146+
false:
147+
%r = call i8 @llvm.ucmp(i32 %x, i32 %y)
148+
ret i8 %r
149+
}

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