[ConstantFolding] Add support for llvm.atan in constant folding. #143416

topperc · 2025-06-09T17:49:57Z

Fixes #143360

Fixes llvm#143360

llvmbot · 2025-06-09T17:50:33Z

@llvm/pr-subscribers-llvm-transforms

Author: Craig Topper (topperc)

Changes

Fixes #143360

Full diff: https://github.com/llvm/llvm-project/pull/143416.diff

2 Files Affected:

(modified) llvm/lib/Analysis/ConstantFolding.cpp (+3)
(added) llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll (+88)

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 7dd7f413783c9..23ea6966fbf6c 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1672,6 +1672,7 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
   case Intrinsic::sincos:
   case Intrinsic::sinh:
   case Intrinsic::cosh:
+  case Intrinsic::atan:
   case Intrinsic::pow:
   case Intrinsic::powi:
   case Intrinsic::ldexp:
@@ -2538,6 +2539,8 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
         return ConstantFoldFP(sinh, APF, Ty);
       case Intrinsic::cosh:
         return ConstantFoldFP(cosh, APF, Ty);
+      case Intrinsic::atan:
+        return ConstantFoldFP(atan, APF, Ty);
       case Intrinsic::sqrt:
         return ConstantFoldFP(sqrt, APF, Ty);
       case Intrinsic::amdgcn_cos:
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll b/llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll
new file mode 100644
index 0000000000000..d824d6d35643d
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll
@@ -0,0 +1,88 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instsimplify < %s | FileCheck %s
+
+define double @test_atan_0() {
+; CHECK-LABEL: define double @test_atan_0() {
+; CHECK-NEXT:    ret double 0.000000e+00
+;
+  %result = call double @llvm.atan.f64(double 0.0)
+  ret double %result
+}
+
+define double @test_atan_one() {
+; CHECK-LABEL: define double @test_atan_one() {
+; CHECK-NEXT:    ret double 0x3FE921FB54442D18
+;
+  %res = call double @llvm.atan.f64(double 1.0)
+  ret double %res
+}
+
+define <2 x double> @test_atan_v2() {
+; CHECK-LABEL: define <2 x double> @test_atan_v2() {
+; CHECK-NEXT:    ret <2 x double> zeroinitializer
+;
+  %result = call <2 x double> @llvm.atan.v2f64(<2 x double> zeroinitializer)
+  ret <2 x double> %result
+}
+
+define double @test_atan_neg0() {
+; CHECK-LABEL: define double @test_atan_neg0() {
+; CHECK-NEXT:    ret double -0.000000e+00
+;
+  %res = call double @llvm.atan.f64(double -0.0)
+  ret double %res
+}
+
+define double @test_atan_poison() {
+; CHECK-LABEL: define double @test_atan_poison() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double poison)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double poison)
+  ret double %res
+}
+
+define double @test_atan_undef() {
+; CHECK-LABEL: define double @test_atan_undef() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double undef)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double undef)
+  ret double %res
+}
+
+define double @test_atan_snan() {
+; CHECK-LABEL: define double @test_atan_snan() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0x7FF0000000000001)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0x7ff0000000000001)
+  ret double %res
+}
+
+define double @test_atan_qnan() {
+; CHECK-LABEL: define double @test_atan_qnan() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0x7FF8000000000000)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0x7ff8000000000000)
+  ret double %res
+}
+
+define double @test_atan_pos_inf() {
+; CHECK-LABEL: define double @test_atan_pos_inf() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0x7FF0000000000000)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0x7ff0000000000000)
+  ret double %res
+}
+
+define double @test_atan_neg_inf() {
+; CHECK-LABEL: define double @test_atan_neg_inf() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0xFFF0000000000000)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0xfff0000000000000)
+  ret double %res
+}

llvmbot · 2025-06-09T17:50:33Z

@llvm/pr-subscribers-llvm-analysis

Author: Craig Topper (topperc)

Changes

Fixes #143360

Full diff: https://github.com/llvm/llvm-project/pull/143416.diff

2 Files Affected:

(modified) llvm/lib/Analysis/ConstantFolding.cpp (+3)
(added) llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll (+88)

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 7dd7f413783c9..23ea6966fbf6c 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1672,6 +1672,7 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
   case Intrinsic::sincos:
   case Intrinsic::sinh:
   case Intrinsic::cosh:
+  case Intrinsic::atan:
   case Intrinsic::pow:
   case Intrinsic::powi:
   case Intrinsic::ldexp:
@@ -2538,6 +2539,8 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
         return ConstantFoldFP(sinh, APF, Ty);
       case Intrinsic::cosh:
         return ConstantFoldFP(cosh, APF, Ty);
+      case Intrinsic::atan:
+        return ConstantFoldFP(atan, APF, Ty);
       case Intrinsic::sqrt:
         return ConstantFoldFP(sqrt, APF, Ty);
       case Intrinsic::amdgcn_cos:
diff --git a/llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll b/llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll
new file mode 100644
index 0000000000000..d824d6d35643d
--- /dev/null
+++ b/llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll
@@ -0,0 +1,88 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=instsimplify < %s | FileCheck %s
+
+define double @test_atan_0() {
+; CHECK-LABEL: define double @test_atan_0() {
+; CHECK-NEXT:    ret double 0.000000e+00
+;
+  %result = call double @llvm.atan.f64(double 0.0)
+  ret double %result
+}
+
+define double @test_atan_one() {
+; CHECK-LABEL: define double @test_atan_one() {
+; CHECK-NEXT:    ret double 0x3FE921FB54442D18
+;
+  %res = call double @llvm.atan.f64(double 1.0)
+  ret double %res
+}
+
+define <2 x double> @test_atan_v2() {
+; CHECK-LABEL: define <2 x double> @test_atan_v2() {
+; CHECK-NEXT:    ret <2 x double> zeroinitializer
+;
+  %result = call <2 x double> @llvm.atan.v2f64(<2 x double> zeroinitializer)
+  ret <2 x double> %result
+}
+
+define double @test_atan_neg0() {
+; CHECK-LABEL: define double @test_atan_neg0() {
+; CHECK-NEXT:    ret double -0.000000e+00
+;
+  %res = call double @llvm.atan.f64(double -0.0)
+  ret double %res
+}
+
+define double @test_atan_poison() {
+; CHECK-LABEL: define double @test_atan_poison() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double poison)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double poison)
+  ret double %res
+}
+
+define double @test_atan_undef() {
+; CHECK-LABEL: define double @test_atan_undef() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double undef)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double undef)
+  ret double %res
+}
+
+define double @test_atan_snan() {
+; CHECK-LABEL: define double @test_atan_snan() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0x7FF0000000000001)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0x7ff0000000000001)
+  ret double %res
+}
+
+define double @test_atan_qnan() {
+; CHECK-LABEL: define double @test_atan_qnan() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0x7FF8000000000000)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0x7ff8000000000000)
+  ret double %res
+}
+
+define double @test_atan_pos_inf() {
+; CHECK-LABEL: define double @test_atan_pos_inf() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0x7FF0000000000000)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0x7ff0000000000000)
+  ret double %res
+}
+
+define double @test_atan_neg_inf() {
+; CHECK-LABEL: define double @test_atan_neg_inf() {
+; CHECK-NEXT:    [[RES:%.*]] = call double @llvm.atan.f64(double 0xFFF0000000000000)
+; CHECK-NEXT:    ret double [[RES]]
+;
+  %res = call double @llvm.atan.f64(double 0xfff0000000000000)
+  ret double %res
+}

github-actions · 2025-06-09T17:52:23Z

⚠️ undef deprecator found issues in your code. ⚠️

You can test this locally with the following command:

git diff -U0 --pickaxe-regex -S '([^a-zA-Z0-9#_-]undef[^a-zA-Z0-9_-]|UndefValue::get)' 'HEAD~1' HEAD llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll llvm/lib/Analysis/ConstantFolding.cpp

The following files introduce new uses of undef:

llvm/test/Transforms/InstSimplify/ConstProp/atan-intrinsic.ll

Undef is now deprecated and should only be used in the rare cases where no replacement is possible. For example, a load of uninitialized memory yields undef. You should use poison values for placeholders instead.

In tests, avoid using undef and having tests that trigger undefined behavior. If you need an operand with some unimportant value, you can add a new argument to the function and use that instead.

For example, this is considered a bad practice:

define void @fn() {
  ...
  br i1 undef, ...
}

Please use the following instead:

define void @fn(i1 %cond) {
  ...
  br i1 %cond, ...
}

Please refer to the Undefined Behavior Manual for more information.

lei137 · 2025-06-10T17:42:08Z

@nikic The testcase is failing for https://lab.llvm.org/buildbot/#/builders/64/builds/4143

The affected test is:

define double @test_atan_neg0() {
; CHECK-LABEL: define double @test_atan_neg0() {
; CHECK-NEXT:    ret double -0.000000e+00
;
  %res = call double @llvm.atan.f64(double -0.0)
  ret double %res
}

This bot is generating:

define double @test_atan_neg0() {
  ret double 0.000000e+00
}

instead of -0.000000e+00. Not sure if the neg is a must for neg0 here.

jcranmer-intel · 2025-06-10T18:15:21Z

atan(-0.0) is -0.0 per IEEE 754, so it's a problem if it's being folded to +0.0.

topperc · 2025-06-10T18:19:34Z

atan(-0.0) is -0.0 per IEEE 754, so it's a problem if it's being folded to +0.0.

I think the constant folding just calls the native libm function linked with the compiler.

jcranmer-intel · 2025-06-10T19:03:42Z

I think the constant folding just calls the native libm function linked with the compiler.

Which we really shouldn't be doing, I know @andykaylor has filed an issue on that in the past. The sooner we can get llvm-libc hand-in-hand with APFloat integration, the better.

andykaylor · 2025-06-10T19:36:03Z

I think the constant folding just calls the native libm function linked with the compiler.

Which we really shouldn't be doing, I know @andykaylor has filed an issue on that in the past. The sooner we can get llvm-libc hand-in-hand with APFloat integration, the better.

The issue I had (and I seem to be in the minority in caring about this) is that when we constant fold a transcendental function by calling the libm function, we run the risk of getting a different answer than we would have gotten if the call had been evaluated at runtime if the user binary is linked with a different math library than the compiler. That's a problem of bitwise reproducibility of results.

If the math library linked with the compiler is simply returning an incorrect result (as seems to be the case here) that's a much bigger problem, but it's a problem for the library.

…m#143416) Fixes llvm#143360

Testcase from llvm#143416 is causing the AIX bot to be red. XFAIL for now till issue can be resolved.

lei137 · 2025-06-11T15:20:43Z

I would like to xfail this tc for now so we can bring the aix bot back to green.
#143723

Testcase from #143416 is causing the AIX bot to be red. XFAIL for now till issue can be resolved.

Testcase from llvm/llvm-project#143416 is causing the AIX bot to be red. XFAIL for now till issue can be resolved.

…m#143416) Fixes llvm#143360

lei137 · 2025-06-12T20:28:11Z

PR to add special handling for -/+0.0: #143962

[ConstantFolding] Add support for llvm.atan in constant folding.

c7d651f

Fixes llvm#143360

topperc requested review from nikic and dtcxzyw June 9, 2025 17:49

llvmbot added llvm:instcombine llvm:analysis llvm:transforms labels Jun 9, 2025

nikic approved these changes Jun 9, 2025

View reviewed changes

topperc merged commit 112490f into llvm:main Jun 9, 2025
10 of 11 checks passed

topperc deleted the pr/atan-constant-folding branch June 9, 2025 19:38

rorth pushed a commit to rorth/llvm-project that referenced this pull request Jun 11, 2025

[ConstantFolding] Add support for llvm.atan in constant folding. (llv…

026ce14

…m#143416) Fixes llvm#143360

lei137 added a commit to lei137/llvm-project that referenced this pull request Jun 11, 2025

[PowerPC][AIX] xfail atan-intrinsic to unblock bot

3885b39

Testcase from llvm#143416 is causing the AIX bot to be red. XFAIL for now till issue can be resolved.

lei137 mentioned this pull request Jun 11, 2025

[PowerPC][AIX] xfail atan-intrinsic to unblock bot #143723

Merged

lei137 added a commit that referenced this pull request Jun 11, 2025

[PowerPC][AIX] xfail atan-intrinsic to unblock bot (#143723)

adfea33

Testcase from #143416 is causing the AIX bot to be red. XFAIL for now till issue can be resolved.

llvm-sync bot pushed a commit to arm/arm-toolchain that referenced this pull request Jun 11, 2025

Automerge: [PowerPC][AIX] xfail atan-intrinsic to unblock bot (#143723)

133f327

Testcase from llvm/llvm-project#143416 is causing the AIX bot to be red. XFAIL for now till issue can be resolved.

DhruvSrivastavaX pushed a commit to DhruvSrivastavaX/lldb-for-aix that referenced this pull request Jun 12, 2025

[ConstantFolding] Add support for llvm.atan in constant folding. (llv…

7fde92f

…m#143416) Fixes llvm#143360

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