[InstCombine] Fold fptrunc(x) ord/uno [ C | fptrunc(y) ] to x ord/uno [ C | y ] - #185844
Merged
Conversation
llvmbot
added
llvm:instcombine
Member
|
@llvm/pr-subscribers-llvm-transforms Author: Kunqiu Chen (Camsyn) ChangesRecognize TWO new patterns and fold them as follows: Fixes #185698 Full diff: https://github.com/llvm/llvm-project/pull/185844.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 7f1ced9505b9b..15ff2eb24600c 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -8290,15 +8290,43 @@ static Instruction *foldFCmpReciprocalAndZero(FCmpInst &I, Instruction *LHSI,
// Transform 'fptrunc(x) cmp C' to 'x cmp ext(C)' if possible.
// Patterns include:
-// fptrunc(x) < C --> x < ext(C)
-// fptrunc(x) <= C --> x <= ext(C)
-// fptrunc(x) > C --> x > ext(C)
-// fptrunc(x) >= C --> x >= ext(C)
+// fptrunc(x) < C --> x < ext(C)
+// fptrunc(x) <= C --> x <= ext(C)
+// fptrunc(x) > C --> x > ext(C)
+// fptrunc(x) >= C --> x >= ext(C)
+// fptrunc(x) ord/uno C --> x ord/uno 0
+// fptrunc(x) ord/uno fptrunc(y) --> x ord/uno y
// where 'ext(C)' is the extension of 'C' to the type of 'x' with a small bias
// due to precision loss.
static Instruction *foldFCmpFpTrunc(FCmpInst &I, const Instruction &FPTrunc,
- const Constant &C) {
+ const Value &CmpRHS) {
FCmpInst::Predicate Pred = I.getPredicate();
+ Type *DestType = FPTrunc.getOperand(0)->getType();
+
+ // Handle ord/uno [C | fptrunc(y)]
+ if (Pred == FCmpInst::FCMP_ORD || Pred == FCmpInst::FCMP_UNO) {
+ Value *RHS;
+ const APFloat *CValue;
+ if (match(&CmpRHS, m_FPTrunc(m_Value(RHS)))) {
+ if (DestType != RHS->getType())
+ return nullptr;
+ } else if (match(&CmpRHS, m_APFloat(CValue))) {
+ assert(!CValue->isNaN() &&
+ "NaN RHS should be folded away by simplifyFCmpInst()");
+ RHS = ConstantFP::getZero(DestType);
+ } else {
+ return nullptr;
+ }
+
+ return new FCmpInst(Pred, FPTrunc.getOperand(0), RHS, "", &I);
+ }
+
+ // Handle <, >, <=, >=
+ const APFloat *CValue;
+ // TODO: support vec
+ if (!match(&CmpRHS, m_APFloat(CValue)))
+ return nullptr;
+
bool RoundDown = false;
if (Pred == FCmpInst::FCMP_OGE || Pred == FCmpInst::FCMP_UGE ||
@@ -8310,10 +8338,6 @@ static Instruction *foldFCmpFpTrunc(FCmpInst &I, const Instruction &FPTrunc,
else
return nullptr;
- const APFloat *CValue;
- if (!match(&C, m_APFloat(CValue)))
- return nullptr;
-
if (CValue->isNaN() || CValue->isInfinity())
return nullptr;
@@ -8332,7 +8356,6 @@ static Instruction *foldFCmpFpTrunc(FCmpInst &I, const Instruction &FPTrunc,
APFloat NextCValue = NextValue(*CValue, RoundDown);
- Type *DestType = FPTrunc.getOperand(0)->getType();
const fltSemantics &DestFltSema =
DestType->getScalarType()->getFltSemantics();
@@ -8354,7 +8377,7 @@ static Instruction *foldFCmpFpTrunc(FCmpInst &I, const Instruction &FPTrunc,
scalbn(ExtCValue + ExtNextCValue, -1, APFloat::rmNearestTiesToEven);
const fltSemantics &SrcFltSema =
- C.getType()->getScalarType()->getFltSemantics();
+ CmpRHS.getType()->getScalarType()->getFltSemantics();
// 'MidValue' might be rounded to 'NextCValue'. Correct it here.
APFloat MidValue = ConvertFltSema(ExtMidValue, SrcFltSema);
@@ -8835,10 +8858,16 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
}
}
- // Handle fcmp with instruction LHS and constant RHS.
Instruction *LHSI;
+ // Handle fcmp with fptrunc LHS
+ if (match(Op0, m_Instruction(LHSI)) &&
+ LHSI->getOpcode() == Instruction::FPTrunc)
+ if (Instruction *NV = foldFCmpFpTrunc(I, *LHSI, *Op1))
+ return NV;
+
+ // Handle fcmp with instruction LHS and constant RHS.
Constant *RHSC;
- if (match(Op0, m_Instruction(LHSI)) && match(Op1, m_Constant(RHSC))) {
+ if (LHSI && match(Op1, m_Constant(RHSC))) {
switch (LHSI->getOpcode()) {
case Instruction::Select:
// fcmp eq (cond ? x : -x), 0 --> fcmp eq x, 0
@@ -8872,10 +8901,6 @@ Instruction *InstCombinerImpl::visitFCmpInst(FCmpInst &I) {
foldCmpLoadFromIndexedGlobal(cast<LoadInst>(LHSI), GEP, I))
return Res;
break;
- case Instruction::FPTrunc:
- if (Instruction *NV = foldFCmpFpTrunc(I, *LHSI, *RHSC))
- return NV;
- break;
}
}
diff --git a/llvm/test/Transforms/InstCombine/fold-fcmp-trunc.ll b/llvm/test/Transforms/InstCombine/fold-fcmp-trunc.ll
index 371f9b6807fe4..e65e31700240f 100644
--- a/llvm/test/Transforms/InstCombine/fold-fcmp-trunc.ll
+++ b/llvm/test/Transforms/InstCombine/fold-fcmp-trunc.ll
@@ -57,6 +57,52 @@ define i1 @fcmp_trunc_zero(double %0) {
ret i1 %result
}
+define i1 @fcmp_trunc_uno(double %0) {
+; CHECK-LABEL: define i1 @fcmp_trunc_uno(
+; CHECK-SAME: double [[TMP0:%.*]]) {
+; CHECK-NEXT: [[RESULT:%.*]] = fcmp uno double [[TMP0]], 0.000000e+00
+; CHECK-NEXT: ret i1 [[RESULT]]
+;
+ %trunc = fptrunc double %0 to float
+ %result = fcmp uno float %trunc, 0.000000e+00
+ ret i1 %result
+}
+
+define i1 @fcmp_trunc_ord_inf(double %0) {
+; CHECK-LABEL: define i1 @fcmp_trunc_ord_inf(
+; CHECK-SAME: double [[TMP0:%.*]]) {
+; CHECK-NEXT: [[RESULT:%.*]] = fcmp ord double [[TMP0]], 0.000000e+00
+; CHECK-NEXT: ret i1 [[RESULT]]
+;
+ %trunc = fptrunc double %0 to float
+ %result = fcmp ord float %trunc, 0x7FF0000000000000
+ ret i1 %result
+}
+
+define i1 @fcmp_trunc_pair_uno(double %x, double %y) {
+; CHECK-LABEL: define i1 @fcmp_trunc_pair_uno(
+; CHECK-SAME: double [[X:%.*]], double [[Y:%.*]]) {
+; CHECK-NEXT: [[RESULT:%.*]] = fcmp uno double [[X]], [[Y]]
+; CHECK-NEXT: ret i1 [[RESULT]]
+;
+ %tx = fptrunc double %x to float
+ %ty = fptrunc double %y to float
+ %result = fcmp uno float %tx, %ty
+ ret i1 %result
+}
+
+define i1 @fcmp_trunc_pair_ord(double %x, double %y) {
+; CHECK-LABEL: define i1 @fcmp_trunc_pair_ord(
+; CHECK-SAME: double [[X:%.*]], double [[Y:%.*]]) {
+; CHECK-NEXT: [[RESULT:%.*]] = fcmp ord double [[X]], [[Y]]
+; CHECK-NEXT: ret i1 [[RESULT]]
+;
+ %tx = fptrunc double %x to float
+ %ty = fptrunc double %y to float
+ %result = fcmp ord float %tx, %ty
+ ret i1 %result
+}
+
define i1 @fcmp_trunc_with_nnan(double %0) {
; CHECK-LABEL: define i1 @fcmp_trunc_with_nnan(
; CHECK-SAME: double [[TMP0:%.*]]) {
@@ -104,7 +150,7 @@ define i1 @fcmp_trunc_with_reassoc(double %0) {
define i1 @fcmp_trunc_with_fast(double %0) {
; CHECK-LABEL: define i1 @fcmp_trunc_with_fast(
; CHECK-SAME: double [[TMP0:%.*]]) {
-; CHECK-NEXT: [[RESULT:%.*]] = fcmp fast oge double [[TMP0]], 0x4058FFFFF0000000
+; CHECK-NEXT: [[RESULT:%.*]] = fcmp fast oge double [[TMP0]], 0x4058FFFFF0000000
; CHECK-NEXT: ret i1 [[RESULT]]
;
%trunc = fptrunc double %0 to float
@@ -327,8 +373,7 @@ define i1 @fcmp_trunc_literal_positive_inf(double %0) {
define i1 @fcmp_trunc_literal_negative_inf(double %0) {
; CHECK-LABEL: define i1 @fcmp_trunc_literal_negative_inf(
; CHECK-SAME: double [[TMP0:%.*]]) {
-; CHECK-NEXT: [[TRUNC:%.*]] = fptrunc double [[TMP0]] to float
-; CHECK-NEXT: [[RESULT:%.*]] = fcmp uno float [[TRUNC]], 0.000000e+00
+; CHECK-NEXT: [[RESULT:%.*]] = fcmp uno double [[TMP0]], 0.000000e+00
; CHECK-NEXT: ret i1 [[RESULT]]
;
%trunc = fptrunc double %0 to float
@@ -671,4 +716,3 @@ define i1 @fcmp_trunc_mn_ppc_fp128(ppc_fp128 %0) {
%result = fcmp uge float %trunc, 0xC7EFFFFF00000000
ret i1 %result
}
-
|
This was referenced Mar 11, 2026
Camsyn
changed the title
fptrunc(x) ord/uno [ C | fptrunc(y) ] to x ord/uno [ C | y ]
dtcxzyw
reviewed
Apr 12, 2026
🪟 Windows x64 Test Results
✅ The build succeeded and all tests passed. |
🐧 Linux x64 Test Results
✅ The build succeeded and all tests passed. |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Recognize TWO new patterns and fold them as follows:
Fixes #185698
Alive2: https://alive2.llvm.org/ce/z/YvXnBJ
IR diff: dtcxzyw/llvm-opt-benchmark#3551
CompTime impact: dtcxzyw/llvm-opt-benchmark#3552