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[IndVarSimplify] Ensure fp values can be represented as consecutive integers #166649

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merged 2 commits into from
Nov 11, 2025
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[IndVarSimplify] Ensure fp values can be represented as consecutive integers #166649

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9100001
[IndVarSimplify] Precommit tests for PR166649 (NFC)
antoniofrighetto Nov 11, 2025
eaf3a91
[IndVarSimplify] Ensure fp values can be represented as exact integers
antoniofrighetto Nov 11, 2025
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18 changes: 16 additions & 2 deletions llvm/lib/Transforms/Scalar/IndVarSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -196,6 +196,18 @@ static bool ConvertToSInt(const APFloat &APF, int64_t &IntVal) {
return true;
}

// Ensure we stay within the bounds of fp values that can be represented as
// integers without gaps, which are 2^24 and 2^53 for IEEE-754 single and double
// precision respectively (both on negative and positive side).
static bool isRepresentableAsExactInteger(ConstantFP *FPVal, int64_t IntVal) {
const auto &InitValueFltSema = FPVal->getValueAPF().getSemantics();
if (!APFloat::isIEEELikeFP(InitValueFltSema))
return false;

return isUIntN(APFloat::semanticsPrecision(InitValueFltSema),
AbsoluteValue(IntVal));
}

/// If the loop has floating induction variable then insert corresponding
/// integer induction variable if possible.
/// For example,
Expand All @@ -212,7 +224,8 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
auto *InitValueVal = dyn_cast<ConstantFP>(PN->getIncomingValue(IncomingEdge));

int64_t InitValue;
if (!InitValueVal || !ConvertToSInt(InitValueVal->getValueAPF(), InitValue))
if (!InitValueVal || !ConvertToSInt(InitValueVal->getValueAPF(), InitValue) ||
!isRepresentableAsExactInteger(InitValueVal, InitValue))
return false;

// Check IV increment. Reject this PN if increment operation is not
Expand Down Expand Up @@ -262,7 +275,8 @@ bool IndVarSimplify::handleFloatingPointIV(Loop *L, PHINode *PN) {
ConstantFP *ExitValueVal = dyn_cast<ConstantFP>(Compare->getOperand(1));
int64_t ExitValue;
if (ExitValueVal == nullptr ||
!ConvertToSInt(ExitValueVal->getValueAPF(), ExitValue))
!ConvertToSInt(ExitValueVal->getValueAPF(), ExitValue) ||
!isRepresentableAsExactInteger(ExitValueVal, ExitValue))
return false;

// Find new predicate for integer comparison.
Expand Down
137 changes: 137 additions & 0 deletions llvm/test/Transforms/IndVarSimplify/floating-point-iv.ll
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Expand Up @@ -417,3 +417,140 @@ loop:
exit:
ret void
}

define void @test_fp_to_int_irrealizable_initval() {
; CHECK-LABEL: @test_fp_to_int_irrealizable_initval(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi float [ 1.000000e+08, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: call void @opaque()
; CHECK-NEXT: [[IV_NEXT]] = fadd float [[IV]], -1.700000e+01
; CHECK-NEXT: [[CMP:%.*]] = fcmp ult float [[IV_NEXT]], 2.500000e+01
; CHECK-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop

loop:
%iv = phi float [ 1.000000e+08, %entry ], [ %iv.next, %loop ]
call void @opaque()
%iv.next = fadd float %iv, -1.700000e+01
%cmp = fcmp ult float %iv.next, 2.500000e+01
br i1 %cmp, label %exit, label %loop

exit:
ret void
}

define void @test_fp_to_int_irrealizable_exitval() {
; CHECK-LABEL: @test_fp_to_int_irrealizable_exitval(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi float [ 2.500000e+01, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: call void @opaque()
; CHECK-NEXT: [[IV_NEXT]] = fadd float [[IV]], 1.700000e+01
; CHECK-NEXT: [[CMP:%.*]] = fcmp ugt float [[IV_NEXT]], 1.000000e+08
; CHECK-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop

loop:
%iv = phi float [ 2.500000e+01, %entry ], [ %iv.next, %loop ]
call void @opaque()
%iv.next = fadd float %iv, 1.700000e+01
%cmp = fcmp ugt float %iv.next, 1.000000e+08
br i1 %cmp, label %exit, label %loop

exit:
ret void
}

define void @test_fp_to_int_irrealizable_negative_exitval() {
; CHECK-LABEL: @test_fp_to_int_irrealizable_negative_exitval(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi float [ -2.500000e+01, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: call void @opaque()
; CHECK-NEXT: [[IV_NEXT]] = fadd float [[IV]], -1.700000e+01
; CHECK-NEXT: [[CMP:%.*]] = fcmp ult float [[IV_NEXT]], -1.000000e+08
; CHECK-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop

loop:
%iv = phi float [ -2.500000e+01, %entry ], [ %iv.next, %loop ]
call void @opaque()
%iv.next = fadd float %iv, -1.700000e+01
%cmp = fcmp ult float %iv.next, -1.000000e+08
br i1 %cmp, label %exit, label %loop

exit:
ret void
}

define void @test_fp_to_int_irrealizable_exitval_pow_2_24() {
; CHECK-LABEL: @test_fp_to_int_irrealizable_exitval_pow_2_24(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi float [ 0.000000e+00, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: call void @opaque()
; CHECK-NEXT: [[IV_NEXT]] = fadd float [[IV]], 1.000000e+00
; CHECK-NEXT: [[CMP:%.*]] = fcmp ugt float [[IV_NEXT]], 0x4170000000000000
; CHECK-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop

loop:
%iv = phi float [ 0.000000e+00, %entry ], [ %iv.next, %loop ]
call void @opaque()
%iv.next = fadd float %iv, 1.000000e+00
%cmp = fcmp ugt float %iv.next, 0x4170000000000000
br i1 %cmp, label %exit, label %loop

exit:
ret void
}

define void @test_fp_to_int_irrealizable_exitval_int64_min() {
; CHECK-LABEL: @test_fp_to_int_irrealizable_exitval_int64_min(
; CHECK-NEXT: entry:
; CHECK-NEXT: br label [[LOOP:%.*]]
; CHECK: loop:
; CHECK-NEXT: [[IV:%.*]] = phi double [ 2.500000e+01, [[ENTRY:%.*]] ], [ [[IV_NEXT:%.*]], [[LOOP]] ]
; CHECK-NEXT: call void @opaque()
; CHECK-NEXT: [[IV_NEXT]] = fadd double [[IV]], 1.700000e+01
; CHECK-NEXT: [[CMP:%.*]] = fcmp ult double [[IV_NEXT]], 0xC3E0000000000000
; CHECK-NEXT: br i1 [[CMP]], label [[EXIT:%.*]], label [[LOOP]]
; CHECK: exit:
; CHECK-NEXT: ret void
;
entry:
br label %loop

loop:
%iv = phi double [ 2.500000e+01, %entry ], [ %iv.next, %loop ]
call void @opaque()
%iv.next = fadd double %iv, 1.700000e+01
%cmp = fcmp ult double %iv.next, 0xC3E0000000000000
br i1 %cmp, label %exit, label %loop

exit:
ret void
}

declare void @opaque()
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