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[InstCombine] Use KnownBits predicate helpers #115874

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merged 2 commits into from
Nov 14, 2024
Merged

[InstCombine] Use KnownBits predicate helpers #115874

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82920a3
[InstCombine] Use KnownBits predicate helpers
nikic Nov 12, 2024
136425b
use new helper
nikic Nov 12, 2024
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72 changes: 11 additions & 61 deletions llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
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Expand Up @@ -6576,6 +6576,16 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
return &I;
}

if (!isa<Constant>(Op0) && Op0Known.isConstant())
return new ICmpInst(
Pred, ConstantExpr::getIntegerValue(Ty, Op0Known.getConstant()), Op1);
if (!isa<Constant>(Op1) && Op1Known.isConstant())
return new ICmpInst(
Pred, Op0, ConstantExpr::getIntegerValue(Ty, Op1Known.getConstant()));

if (std::optional<bool> Res = ICmpInst::compare(Op0Known, Op1Known, Pred))
return replaceInstUsesWith(I, ConstantInt::getBool(I.getType(), *Res));

// Given the known and unknown bits, compute a range that the LHS could be
// in. Compute the Min, Max and RHS values based on the known bits. For the
// EQ and NE we use unsigned values.
Expand All @@ -6593,14 +6603,6 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
Op1Max = Op1Known.getMaxValue();
}

// If Min and Max are known to be the same, then SimplifyDemandedBits figured
// out that the LHS or RHS is a constant. Constant fold this now, so that
// code below can assume that Min != Max.
if (!isa<Constant>(Op0) && Op0Min == Op0Max)
return new ICmpInst(Pred, ConstantExpr::getIntegerValue(Ty, Op0Min), Op1);
if (!isa<Constant>(Op1) && Op1Min == Op1Max)
return new ICmpInst(Pred, Op0, ConstantExpr::getIntegerValue(Ty, Op1Min));

// Don't break up a clamp pattern -- (min(max X, Y), Z) -- by replacing a
// min/max canonical compare with some other compare. That could lead to
// conflict with select canonicalization and infinite looping.
Expand Down Expand Up @@ -6682,13 +6684,9 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
// simplify this comparison. For example, (x&4) < 8 is always true.
switch (Pred) {
default:
llvm_unreachable("Unknown icmp opcode!");
break;
case ICmpInst::ICMP_EQ:
case ICmpInst::ICMP_NE: {
if (Op0Max.ult(Op1Min) || Op0Min.ugt(Op1Max))
return replaceInstUsesWith(
I, ConstantInt::getBool(I.getType(), Pred == CmpInst::ICMP_NE));

// If all bits are known zero except for one, then we know at most one bit
// is set. If the comparison is against zero, then this is a check to see if
// *that* bit is set.
Expand Down Expand Up @@ -6728,67 +6726,19 @@ Instruction *InstCombinerImpl::foldICmpUsingKnownBits(ICmpInst &I) {
ConstantInt::getNullValue(Op1->getType()));
break;
}
case ICmpInst::ICMP_ULT: {
if (Op0Max.ult(Op1Min)) // A <u B -> true if max(A) < min(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Min.uge(Op1Max)) // A <u B -> false if min(A) >= max(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
break;
}
case ICmpInst::ICMP_UGT: {
if (Op0Min.ugt(Op1Max)) // A >u B -> true if min(A) > max(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Max.ule(Op1Min)) // A >u B -> false if max(A) <= max(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
break;
}
case ICmpInst::ICMP_SLT: {
if (Op0Max.slt(Op1Min)) // A <s B -> true if max(A) < min(C)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Min.sge(Op1Max)) // A <s B -> false if min(A) >= max(C)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
break;
}
case ICmpInst::ICMP_SGT: {
if (Op0Min.sgt(Op1Max)) // A >s B -> true if min(A) > max(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Max.sle(Op1Min)) // A >s B -> false if max(A) <= min(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
break;
}
case ICmpInst::ICMP_SGE:
assert(!isa<ConstantInt>(Op1) && "ICMP_SGE with ConstantInt not folded!");
if (Op0Min.sge(Op1Max)) // A >=s B -> true if min(A) >= max(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Max.slt(Op1Min)) // A >=s B -> false if max(A) < min(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
if (Op1Min == Op0Max) // A >=s B -> A == B if max(A) == min(B)
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
break;
case ICmpInst::ICMP_SLE:
assert(!isa<ConstantInt>(Op1) && "ICMP_SLE with ConstantInt not folded!");
if (Op0Max.sle(Op1Min)) // A <=s B -> true if max(A) <= min(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Min.sgt(Op1Max)) // A <=s B -> false if min(A) > max(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
if (Op1Max == Op0Min) // A <=s B -> A == B if min(A) == max(B)
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
break;
case ICmpInst::ICMP_UGE:
assert(!isa<ConstantInt>(Op1) && "ICMP_UGE with ConstantInt not folded!");
if (Op0Min.uge(Op1Max)) // A >=u B -> true if min(A) >= max(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Max.ult(Op1Min)) // A >=u B -> false if max(A) < min(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
if (Op1Min == Op0Max) // A >=u B -> A == B if max(A) == min(B)
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
break;
case ICmpInst::ICMP_ULE:
assert(!isa<ConstantInt>(Op1) && "ICMP_ULE with ConstantInt not folded!");
if (Op0Max.ule(Op1Min)) // A <=u B -> true if max(A) <= min(B)
return replaceInstUsesWith(I, ConstantInt::getTrue(I.getType()));
if (Op0Min.ugt(Op1Max)) // A <=u B -> false if min(A) > max(B)
return replaceInstUsesWith(I, ConstantInt::getFalse(I.getType()));
if (Op1Max == Op0Min) // A <=u B -> A == B if min(A) == max(B)
return new ICmpInst(ICmpInst::ICMP_EQ, Op0, Op1);
break;
Expand Down
4 changes: 1 addition & 3 deletions llvm/test/Transforms/InstCombine/icmp-gep.ll
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Expand Up @@ -583,9 +583,7 @@ define i1 @gep_nusw(ptr %p, i64 %a, i64 %b, i64 %c, i64 %d) {

define i1 @pointer_icmp_aligned_with_offset(ptr align 8 %a, ptr align 8 %a2) {
; CHECK-LABEL: @pointer_icmp_aligned_with_offset(
; CHECK-NEXT: [[GEP:%.*]] = getelementptr i8, ptr [[A:%.*]], i64 4
; CHECK-NEXT: [[CMP:%.*]] = icmp eq ptr [[GEP]], [[A2:%.*]]
; CHECK-NEXT: ret i1 [[CMP]]
; CHECK-NEXT: ret i1 false
;
%gep = getelementptr i8, ptr %a, i64 4
%cmp = icmp eq ptr %gep, %a2
Expand Down
4 changes: 2 additions & 2 deletions llvm/test/Transforms/InstCombine/mul-inseltpoison.ll
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Expand Up @@ -570,12 +570,12 @@ define i64 @test30(i32 %A, i32 %B) {
@PR22087 = external global i32
define i32 @test31(i32 %V) {
; CHECK-LABEL: @test31(
; CHECK-NEXT: [[CMP:%.*]] = icmp ne ptr inttoptr (i64 1 to ptr), @PR22087
; CHECK-NEXT: [[CMP:%.*]] = icmp ne ptr inttoptr (i64 4 to ptr), @PR22087
; CHECK-NEXT: [[EXT:%.*]] = zext i1 [[CMP]] to i32
; CHECK-NEXT: [[MUL1:%.*]] = shl i32 [[V:%.*]], [[EXT]]
; CHECK-NEXT: ret i32 [[MUL1]]
;
%cmp = icmp ne ptr inttoptr (i64 1 to ptr), @PR22087
%cmp = icmp ne ptr inttoptr (i64 4 to ptr), @PR22087
%ext = zext i1 %cmp to i32
%shl = shl i32 1, %ext
%mul = mul i32 %V, %shl
Expand Down
4 changes: 2 additions & 2 deletions llvm/test/Transforms/InstCombine/mul.ll
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Expand Up @@ -1152,12 +1152,12 @@ define i64 @test30(i32 %A, i32 %B) {
@PR22087 = external global i32
define i32 @test31(i32 %V) {
; CHECK-LABEL: @test31(
; CHECK-NEXT: [[CMP:%.*]] = icmp ne ptr inttoptr (i64 1 to ptr), @PR22087
; CHECK-NEXT: [[CMP:%.*]] = icmp ne ptr inttoptr (i64 4 to ptr), @PR22087
; CHECK-NEXT: [[EXT:%.*]] = zext i1 [[CMP]] to i32
; CHECK-NEXT: [[MUL1:%.*]] = shl i32 [[V:%.*]], [[EXT]]
; CHECK-NEXT: ret i32 [[MUL1]]
;
%cmp = icmp ne ptr inttoptr (i64 1 to ptr), @PR22087
%cmp = icmp ne ptr inttoptr (i64 4 to ptr), @PR22087
%ext = zext i1 %cmp to i32
%shl = shl i32 1, %ext
%mul = mul i32 %V, %shl
Expand Down
2 changes: 1 addition & 1 deletion llvm/test/Transforms/InstCombine/shift-amount-reassociation-in-bittest.ll
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Expand Up @@ -669,7 +669,7 @@ define <2 x i1> @n38_overshift(<2 x i32> %x, <2 x i32> %y) {
}

; As usual, don't crash given constantexpr's :/
@f.a = internal global i16 0
@f.a = internal global i16 0, align 1
define i1 @constantexpr() {
; CHECK-LABEL: @constantexpr(
; CHECK-NEXT: entry:
Expand Down
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