[llvm] [ConstantFold] Fold `erf` and `erff` when the input parameter is a constant value. (PR #113079)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: None (c8ef)

<details>
<summary>Changes</summary>

This patch adds support for constant folding for the `erf` and `erff` libc functions.

---
Full diff: https://github.com/llvm/llvm-project/pull/113079.diff


2 Files Affected:

- (modified) llvm/lib/Analysis/ConstantFolding.cpp (+7-2) 
- (added) llvm/test/Transforms/InstCombine/erf.ll (+185) 


``````````diff
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index c0104d2bc26112..082df2972dfda1 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1671,8 +1671,8 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
            Name == "cos" || Name == "cosf" ||
            Name == "cosh" || Name == "coshf";
   case 'e':
-    return Name == "exp" || Name == "expf" ||
-           Name == "exp2" || Name == "exp2f";
+    return Name == "exp" || Name == "expf" || Name == "exp2" ||
+           Name == "exp2f" || Name == "erf" || Name == "erff";
   case 'f':
     return Name == "fabs" || Name == "fabsf" ||
            Name == "floor" || Name == "floorf" ||
@@ -2411,6 +2411,11 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
       break;
     case LibFunc_logl:
       return nullptr;
+    case LibFunc_erf:
+    case LibFunc_erff:
+      if (TLI->has(Func))
+        return ConstantFoldFP(erf, APF, Ty);
+      break;
     case LibFunc_nearbyint:
     case LibFunc_nearbyintf:
     case LibFunc_rint:
diff --git a/llvm/test/Transforms/InstCombine/erf.ll b/llvm/test/Transforms/InstCombine/erf.ll
new file mode 100644
index 00000000000000..e2f1abca074669
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/erf.ll
@@ -0,0 +1,185 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -S | FileCheck %s
+
+define float @erff_const() {
+; CHECK-LABEL: define float @erff_const() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 5.000000e-01)
+; CHECK-NEXT:    ret float 0x3FE0A7EF60000000
+;
+  %r = call float @erff(float 5.000000e-01)
+  ret float %r
+}
+
+define double @erf_const() {
+; CHECK-LABEL: define double @erf_const() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double -5.000000e-01)
+; CHECK-NEXT:    ret double 0xBFE0A7EF5C18EDD2
+;
+  %r = call double @erf(double -5.000000e-01)
+  ret double %r
+}
+
+define float @erff_zero() {
+; CHECK-LABEL: define float @erff_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0.000000e+00)
+; CHECK-NEXT:    ret float 0.000000e+00
+;
+  %r = call float @erff(float 0.000000e+00)
+  ret float %r
+}
+
+define double @erf_zero() {
+; CHECK-LABEL: define double @erf_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0.000000e+00)
+; CHECK-NEXT:    ret double 0.000000e+00
+;
+  %r = call double @erf(double 0.000000e+00)
+  ret double %r
+}
+
+define float @erff_neg_zero() {
+; CHECK-LABEL: define float @erff_neg_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float -0.000000e+00)
+; CHECK-NEXT:    ret float -0.000000e+00
+;
+  %r = call float @erff(float -0.000000e+00)
+  ret float %r
+}
+
+define double @erf_neg_zero() {
+; CHECK-LABEL: define double @erf_neg_zero() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double -0.000000e+00)
+; CHECK-NEXT:    ret double -0.000000e+00
+;
+  %r = call double @erf(double -0.000000e+00)
+  ret double %r
+}
+
+define float @erff_inf() {
+; CHECK-LABEL: define float @erff_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0x7FF0000000000000)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0x7FF0000000000000)
+  ret float %r
+}
+
+define double @erf_inf() {
+; CHECK-LABEL: define double @erf_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0x7FF0000000000000)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0x7FF0000000000000)
+  ret double %r
+}
+
+define float @erff_inf_memory_none() {
+; CHECK-LABEL: define float @erff_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0x7FF0000000000000) #[[ATTR0:[0-9]+]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0x7FF0000000000000) readnone
+  ret float %r
+}
+
+define double @erf_inf_memory_none() {
+; CHECK-LABEL: define double @erf_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0x7FF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0x7FF0000000000000) readnone
+  ret double %r
+}
+
+define float @erff_neg_inf() {
+; CHECK-LABEL: define float @erff_neg_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0xFFF0000000000000)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0xFFF0000000000000)
+  ret float %r
+}
+
+define double @erf_neg_inf() {
+; CHECK-LABEL: define double @erf_neg_inf() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0xFFF0000000000000)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0xFFF0000000000000)
+  ret double %r
+}
+
+define float @erff_neg_inf_memory_none() {
+; CHECK-LABEL: define float @erff_neg_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0xFFF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0xFFF0000000000000) readnone
+  ret float %r
+}
+
+define double @erf_neg_inf_memory_none() {
+; CHECK-LABEL: define double @erf_neg_inf_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0xFFF0000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0xFFF0000000000000) readnone
+  ret double %r
+}
+
+define float @erff_nan() {
+; CHECK-LABEL: define float @erff_nan() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0x7FF8000000000000)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0x7FF8000000000000)
+  ret float %r
+}
+
+define double @erf_nan() {
+; CHECK-LABEL: define double @erf_nan() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0x7FF8000000000000)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0x7FF8000000000000)
+  ret double %r
+}
+
+define float @erff_nan_memory_none() {
+; CHECK-LABEL: define float @erff_nan_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0x7FF8000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0x7FF8000000000000) readnone
+  ret float %r
+}
+
+define double @erf_nan_memory_none() {
+; CHECK-LABEL: define double @erf_nan_memory_none() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0x7FF8000000000000) #[[ATTR0]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0x7FF8000000000000) readnone
+  ret double %r
+}
+
+define float @erff_poison() {
+; CHECK-LABEL: define float @erff_poison() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float poison)
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float poison)
+  ret float %r
+}
+
+define double @erf_poison() {
+; CHECK-LABEL: define double @erf_poison() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double poison)
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double poison)
+  ret double %r
+}
+
+declare float @erff(float)
+declare double @erf(double)

``````````

</details>


https://github.com/llvm/llvm-project/pull/113079