[InstCombine] Optimize redundant floating point comparisons in `or`/`and` inst's #158097

Rajveer100 · 2025-09-11T15:26:54Z

We can eliminate one of the fcmp when we have two same olt or ogt instructions matched in or/and simplification.

llvmbot · 2025-09-11T15:27:27Z

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Author: Rajveer Singh Bharadwaj (Rajveer100)

Changes

Resolves #157371

We can eliminate one of the fcmp when we have two same olt or ogt instructions matched in or simplification.

Full diff: https://github.com/llvm/llvm-project/pull/158097.diff

3 Files Affected:

(modified) llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp (+24)
(modified) llvm/test/Transforms/InstCombine/or-fcmp.ll (+60)
(added) llvm/test/Transforms/InstCombine/redundant-fcmp.ll (+54)

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
index 6e46898634070..0719932e1394d 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
@@ -4514,6 +4514,30 @@ Instruction *InstCombinerImpl::visitOr(BinaryOperator &I) {
     if (Value *V = SimplifyAddWithRemainder(I))
       return replaceInstUsesWith(I, V);
 
+  Value *V0, *V1;
+  const APFloat *V0Op1, *V1Op1;
+  if (match(Op0, m_SpecificFCmp(FCmpInst::FCMP_OLT, m_Value(V0),
+                                m_APFloat(V0Op1))) &&
+      match(Op1, m_SpecificFCmp(FCmpInst::FCMP_OLT, m_Value(V1),
+                                m_APFloat(V1Op1)))) {
+    if (V0 == V1) {
+      if (V0Op1 > V1Op1)
+        replaceInstUsesWith(I, Op0);
+      else if (V1Op1 > V0Op1)
+        replaceInstUsesWith(I, Op1);
+    }
+  } else if (match(Op0, m_SpecificFCmp(FCmpInst::FCMP_OGT, m_Value(V0),
+                                m_APFloat(V0Op1))) &&
+      match(Op1, m_SpecificFCmp(FCmpInst::FCMP_OGT, m_Value(V1),
+                                m_APFloat(V1Op1)))) {
+    if (V0 == V1) {
+      if (V0Op1 < V1Op1)
+        replaceInstUsesWith(I, Op1);
+      else if (V1Op1 < V0Op1)
+        replaceInstUsesWith(I, Op0);
+    }
+  }
+
   return nullptr;
 }
 
diff --git a/llvm/test/Transforms/InstCombine/or-fcmp.ll b/llvm/test/Transforms/InstCombine/or-fcmp.ll
index 193fe4b5cc722..926f66f622914 100644
--- a/llvm/test/Transforms/InstCombine/or-fcmp.ll
+++ b/llvm/test/Transforms/InstCombine/or-fcmp.ll
@@ -4657,3 +4657,63 @@ define i1 @or_fcmp_reassoc4(i1 %x, double %a, double %b) {
   %retval = or i1 %cmp1, %or
   ret i1 %retval
 }
+
+define i1 @or_fcmp_redundant1(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant1(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V1:%.*]] = fcmp nsz olt double [[V0]], 1.000000e-02
+; CHECK-NEXT:    [[V2:%.*]] = fcmp nsz olt double [[V0]], 1.990000e+00
+; CHECK-NEXT:    [[V3:%.*]] = or i1 [[V1]], [[V2]]
+; CHECK-NEXT:    ret i1 [[V2]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz olt double %v0, 1.000000e-02
+  %v2 = fcmp nsz olt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
+
+define i1 @or_fcmp_redundant2(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant2(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V1:%.*]] = fcmp nsz olt double [[V0]], 2.300000e+00
+; CHECK-NEXT:    [[V2:%.*]] = fcmp nsz olt double [[V0]], 1.990000e+00
+; CHECK-NEXT:    [[V3:%.*]] = or i1 [[V1]], [[V2]]
+; CHECK-NEXT:    ret i1 [[V1]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz olt double %v0, 2.300000e+00
+  %v2 = fcmp nsz olt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
+
+define i1 @or_fcmp_redundant3(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant3(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V1:%.*]] = fcmp nsz ogt double [[V0]], 1.000000e-02
+; CHECK-NEXT:    [[V2:%.*]] = fcmp nsz olt double [[V0]], 1.990000e+00
+; CHECK-NEXT:    [[V3:%.*]] = or i1 [[V1]], [[V2]]
+; CHECK-NEXT:    ret i1 [[V3]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz ogt double %v0, 1.000000e-02
+  %v2 = fcmp nsz olt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
+
+define i1 @or_fcmp_redundant4(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant4(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V1:%.*]] = fcmp nsz ogt double [[V0]], 2.300000e+00
+; CHECK-NEXT:    [[V2:%.*]] = fcmp nsz ogt double [[V0]], 1.990000e+00
+; CHECK-NEXT:    [[V3:%.*]] = or i1 [[V1]], [[V2]]
+; CHECK-NEXT:    ret i1 [[V1]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz ogt double %v0, 2.300000e+00
+  %v2 = fcmp nsz ogt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
diff --git a/llvm/test/Transforms/InstCombine/redundant-fcmp.ll b/llvm/test/Transforms/InstCombine/redundant-fcmp.ll
new file mode 100644
index 0000000000000..934d9e6c46507
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/redundant-fcmp.ll
@@ -0,0 +1,54 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -O3 -S | FileCheck %s
+
+define i1 @or_fcmp_redundant1(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant1(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V2:%.*]] = fcmp nsz olt double [[V0]], 1.990000e+00
+; CHECK-NEXT:    ret i1 [[V2]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz olt double %v0, 1.000000e-02
+  %v2 = fcmp nsz olt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
+
+define i1 @or_fcmp_redundant2(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant2(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V1:%.*]] = fcmp nsz olt double [[V0]], 2.300000e+00
+; CHECK-NEXT:    ret i1 [[V1]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz olt double %v0, 2.300000e+00
+  %v2 = fcmp nsz olt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
+
+define i1 @or_fcmp_redundant3(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant3(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V3:%.*]] = fcmp nsz ogt double [[V0]], 1.990000e+00
+; CHECK-NEXT:    ret i1 [[V3]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz ogt double %v0, 1.000000e-02
+  %v2 = fcmp nsz ogt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}
+
+define i1 @or_fcmp_redundant4(ptr %arg0) {
+; CHECK-LABEL: @or_fcmp_redundant4(
+; CHECK-NEXT:    [[V0:%.*]] = load double, ptr [[ARG0:%.*]], align 8
+; CHECK-NEXT:    [[V1:%.*]] = fcmp nsz ogt double [[V0]], 2.300000e+00
+; CHECK-NEXT:    ret i1 [[V1]]
+;
+  %v0 = load double, ptr %arg0, align 8
+  %v1 = fcmp nsz ogt double %v0, 2.300000e+00
+  %v2 = fcmp nsz ogt double %v0, 1.990000e+00
+  %v3 = or i1 %v1, %v2
+  ret i1 %v3
+}

dtcxzyw · 2025-09-11T15:30:30Z

@zyw-bot mfuzz

llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp

XChy

Should check !isAnd if you only fold the pattern or(fcmp, fcmp).

llvm/lib/Analysis/InstructionSimplify.cpp

llvm/test/Transforms/InstCombine/or-fcmp.ll

XChy · 2025-09-13T08:56:48Z

General proof: proof

Rajveer100 · 2025-09-13T11:03:09Z

Should check !isAnd if you only fold the pattern or(fcmp, fcmp).

Yeah, for the and case we just return the other op.

github-actions · 2025-09-13T11:33:17Z

✅ With the latest revision this PR passed the C/C++ code formatter.

Rajveer100 · 2025-09-14T11:07:51Z

@dtcxzyw
Gentle ping!

llvm/lib/Analysis/InstructionSimplify.cpp

Rajveer100 · 2025-09-14T13:22:04Z

CI looks good now.

llvm/test/Transforms/InstCombine/or-fcmp.ll

llvm/lib/Analysis/InstructionSimplify.cpp

dtcxzyw

LG. As a follow-up, we can use the ConstantFPRange API to generalize this pattern (makeExactFCmpRegion + contains).

llvm/test/Transforms/InstCombine/redundant-fcmp.ll

…and` inst's Resolves llvm#157371 We can eliminate one of the `fcmp` when we have two same `olt` or `ogt` instructions matched in `or`/`and` simplification.

…parisons with `ConstantFPRange` Follow up of llvm#158097 Similar to `simplifyAndOrOfICmpsWithConstants`, we can do so for floating point comparisons.

…parisons with `ConstantFPRange` (#159315) Follow up of #158097 Similar to `simplifyAndOrOfICmpsWithConstants`, we can do so for floating point comparisons.

Rajveer100 requested a review from dtcxzyw September 11, 2025 15:26

Rajveer100 requested a review from nikic as a code owner September 11, 2025 15:26

llvmbot added llvm:instcombine Covers the InstCombine, InstSimplify and AggressiveInstCombine passes llvm:transforms labels Sep 11, 2025

Rajveer100 force-pushed the opt-redundant-fcmp branch from 45430d5 to 7a8a3b0 Compare September 11, 2025 15:27

Rajveer100 added the floating-point Floating-point math label Sep 11, 2025

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Fuzz PR158097 dtcxzyw/llvm-mutation-based-fuzz-service#98

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Rajveer100 changed the title ~~[InstCombine] Optimize redundant floating point comparisons in or inst~~ [InstCombine] Optimize redundant floating point comparisons in or/and inst's Sep 13, 2025

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[InstCombine] Optimize redundant floating point comparisons in or/`…

b7a8db4

…and` inst's Resolves llvm#157371 We can eliminate one of the `fcmp` when we have two same `olt` or `ogt` instructions matched in `or`/`and` simplification.

Rajveer100 force-pushed the opt-redundant-fcmp branch from 1501af4 to b7a8db4 Compare September 16, 2025 14:42

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[InstCombine] Generalise optimisation of redundant floating point comparisons with ConstantFPRange #159315

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[InstCombine] Optimize redundant floating point comparisons in `or`/`and` inst's #158097

[InstCombine] Optimize redundant floating point comparisons in `or`/`and` inst's #158097

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