[InstCombine] Fold tan(x) * cos(x) => sin(x)

llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp

@@ -1073,6 +1073,16 @@ Instruction *InstCombinerImpl::visitFMul(BinaryOperator &I) {
     return Result;
   }
 
+  // tan(X) * cos(X) -> sin(X)
+  if (I.hasAllowReassoc() && Op0->hasOneUse() && Op1->hasOneUse()) {
+    Value *X;
+    if (match(Op0, m_Intrinsic<Intrinsic::tan>(m_Value(X))) &&
+        match(Op1, m_Intrinsic<Intrinsic::cos>(m_Specific(X)))) {
+      Value *Sin = Builder.CreateUnaryIntrinsic(Intrinsic::sin, X, &I);
+      return replaceInstUsesWith(I, Sin);
+    }
+  }
+
   return nullptr;
 }
 

llvm/test/Transforms/InstCombine/fmul-tan-cos.ll

@@ -0,0 +1,123 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instcombine < %s | FileCheck %s
+
+define double @fmul_tan_cos(double %a) {
+; CHECK-LABEL: define double @fmul_tan_cos(
+; CHECK-SAME: double [[A:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call double @llvm.tan.f64(double [[A]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call double @llvm.cos.f64(double [[A]])
+; CHECK-NEXT:    [[RES:%.*]] = fmul double [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %1 = call double @llvm.tan.f64(double %a)
+  %2 = call double @llvm.cos.f64(double %a)
+  %res = fmul double %1, %2
+  ret double %res
+}
+
+define double @fmul_strict_tan_strict_cos_reassoc(double %a) {
+; CHECK-LABEL: define double @fmul_strict_tan_strict_cos_reassoc(
+; CHECK-SAME: double [[A:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call double @llvm.tan.f64(double [[A]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call reassoc double @llvm.cos.f64(double [[A]])
+; CHECK-NEXT:    [[RES:%.*]] = fmul double [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %1 = call double @llvm.tan.f64(double %a)
+  %2 = call reassoc double @llvm.cos.f64(double %a)
+  %res = fmul double %1, %2
+  ret double %res
+}
+
+define double @fmul_reassoc_tan_strict_cos_strict(double %a, ptr dereferenceable(2) %dummy) {
+; CHECK-LABEL: define double @fmul_reassoc_tan_strict_cos_strict(
+; CHECK-SAME: double [[A:%.*]], ptr dereferenceable(2) [[DUMMY:%.*]]) {
+; CHECK-NEXT:    [[RES:%.*]] = call reassoc double @llvm.sin.f64(double [[A]])
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %1 = call double @llvm.tan.f64(double %a)
+  %2 = call double @llvm.cos.f64(double %a)
+  %res = fmul reassoc double %1, %2
+  ret double %res
+}
+
+define double @fmul_reassoc_tan_reassoc_cos_strict(double %a) {
+; CHECK-LABEL: define double @fmul_reassoc_tan_reassoc_cos_strict(
+; CHECK-SAME: double [[A:%.*]]) {
+; CHECK-NEXT:    [[RES:%.*]] = call reassoc double @llvm.sin.f64(double [[A]])
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %1 = call reassoc double @llvm.tan.f64(double %a)
+  %2 = call double @llvm.cos.f64(double %a)
+  %res = fmul reassoc double %1, %2
+  ret double %res
+}
+
+define double @fmul_tan_cos_reassoc_multiple_uses(double %a) {
+; CHECK-LABEL: define double @fmul_tan_cos_reassoc_multiple_uses(
+; CHECK-SAME: double [[A:%.*]]) {
+; CHECK-NEXT:    [[TMP1:%.*]] = call reassoc double @llvm.tan.f64(double [[A]])
+; CHECK-NEXT:    [[TMP2:%.*]] = call reassoc double @llvm.cos.f64(double [[A]])
+; CHECK-NEXT:    [[RES:%.*]] = fmul reassoc double [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    call void @use(double [[TMP2]])
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %1 = call reassoc double @llvm.tan.f64(double %a)
+  %2 = call reassoc double @llvm.cos.f64(double %a)
+  %res = fmul reassoc double %1, %2
+  call void @use(double %2)
+  ret double %res
+}
+
+define double @fmul_tan_cos_reassoc(double %a) {
+; CHECK-LABEL: define double @fmul_tan_cos_reassoc(
+; CHECK-SAME: double [[A:%.*]]) {
+; CHECK-NEXT:    [[RES:%.*]] = call reassoc double @llvm.sin.f64(double [[A]])
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %1 = call reassoc double @llvm.tan.f64(double %a)
+  %2 = call reassoc double @llvm.cos.f64(double %a)
+  %res = fmul reassoc double %1, %2
+  ret double %res
+}
+
+define float @fmul_tanf_cosf_reassoc(float %a) {
+; CHECK-LABEL: define float @fmul_tanf_cosf_reassoc(
+; CHECK-SAME: float [[A:%.*]]) {
+; CHECK-NEXT:    [[RES:%.*]] = call reassoc float @llvm.sin.f32(float [[A]])
+; CHECK-NEXT:    ret float [[RES]]
+;
+  %1 = call reassoc float @llvm.tan.f32(float %a)
+  %2 = call reassoc float @llvm.cos.f32(float %a)
+  %res = fmul reassoc float %1, %2
+  ret float %res
+}
+
+define fp128 @fmul_tanfp128_cosfp128_reassoc(fp128 %a) {
+; CHECK-LABEL: define fp128 @fmul_tanfp128_cosfp128_reassoc(
+; CHECK-SAME: fp128 [[A:%.*]]) {
+; CHECK-NEXT:    [[RES:%.*]] = call reassoc fp128 @llvm.sin.f128(fp128 [[A]])
+; CHECK-NEXT:    ret fp128 [[RES]]
+;
+  %1 = call reassoc fp128 @llvm.tan.fp128(fp128 %a)
+  %2 = call reassoc fp128 @llvm.cos.fp128(fp128 %a)
+  %res = fmul reassoc fp128 %1, %2
+  ret fp128 %res
+}
+
+declare double @llvm.sin.f64(double) #1
+declare float @llvm.sin.f32(float) #1
+declare fp128 @llvm.sin.fp128(fp128) #1
+
+declare double @llvm.cos.f64(double) #1
+declare float @llvm.cos.f32(float) #1
+declare fp128 @llvm.cos.fp128(fp128) #1
+
+declare double @llvm.tan.f64(double) #1
+declare float @llvm.tan.f32(float) #1
+declare fp128 @llvm.tan.fp128(fp128) #1
+
+declare void @use(double)
+
+attributes #0 = { nounwind readnone speculatable }
+attributes #1 = { nounwind readnone }