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

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

2 files changed, 228 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 530e928..c5a2c2f 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1672,8 +1672,8 @@ 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" ||
@@ -2412,6 +2412,11 @@ 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:
@@ -3597,7 +3602,6 @@ bool llvm::isMathLibCallNoop(const CallBase *Call,
         // Per POSIX, this MAY fail if Op is denormal. We choose not failing.
         return true;
 
-
       case LibFunc_asinl:
       case LibFunc_asin:
       case LibFunc_asinf:
diff --git a/llvm/test/Transforms/InstCombine/erf.ll b/llvm/test/Transforms/InstCombine/erf.ll
new file mode 100644
index 0000000..13d6545
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/erf.ll
@@ -0,0 +1,221 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt < %s -passes=instcombine -mtriple x86_64-unknown-linux-gnu -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) #[[ATTR1:[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) #[[ATTR1]]
+; 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) #[[ATTR1]]
+; 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) #[[ATTR1]]
+; 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) #[[ATTR1]]
+; 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) #[[ATTR1]]
+; 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
+}
+
+define float @erff_const_strictfp() {
+; CHECK-LABEL: define float @erff_const_strictfp() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 5.000000e-01) #[[ATTR2:[0-9]+]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 5.000000e-01) strictfp
+  ret float %r
+}
+
+define double @erf_const_strictfp() {
+; CHECK-LABEL: define double @erf_const_strictfp() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double -5.000000e-01) #[[ATTR2]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double -5.000000e-01) strictfp
+  ret double %r
+}
+
+define float @erff_nan_strictfp() {
+; CHECK-LABEL: define float @erff_nan_strictfp() {
+; CHECK-NEXT:    [[R:%.*]] = call float @erff(float 0x7FF8000000000000) #[[ATTR2]]
+; CHECK-NEXT:    ret float [[R]]
+;
+  %r = call float @erff(float 0x7FF8000000000000) strictfp
+  ret float %r
+}
+
+define double @erf_nan_strictfp() {
+; CHECK-LABEL: define double @erf_nan_strictfp() {
+; CHECK-NEXT:    [[R:%.*]] = call double @erf(double 0x7FF8000000000000) #[[ATTR2]]
+; CHECK-NEXT:    ret double [[R]]
+;
+  %r = call double @erf(double 0x7FF8000000000000) strictfp
+  ret double %r
+}
+
+declare float @erff(float) willreturn
+declare double @erf(double) willreturn