[ConstantFold] Fold `tgamma` and `tgammaf` when the input parameter is a constant value. (#114065)

This patch adds support for constant folding for the `tgamma` and
`tgammaf` libc functions.

1 files changed, 16 insertions, 3 deletions

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index c5a2c2f..a96c3be 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -57,6 +57,7 @@
 #include <cassert>
 #include <cerrno>
 #include <cfenv>
+#include <cfloat>
 #include <cmath>
 #include <cstdint>
 
@@ -1698,9 +1699,9 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
            Name == "sinh" || Name == "sinhf" ||
            Name == "sqrt" || Name == "sqrtf";
   case 't':
-    return Name == "tan" || Name == "tanf" ||
-           Name == "tanh" || Name == "tanhf" ||
-           Name == "trunc" || Name == "truncf";
+    return Name == "tan" || Name == "tanf" || Name == "tanh" ||
+           Name == "tanhf" || Name == "trunc" || Name == "truncf" ||
+           Name == "tgamma" || Name == "tgammaf";
   case '_':
     // Check for various function names that get used for the math functions
     // when the header files are preprocessed with the macro
@@ -2417,6 +2418,14 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
       if (TLI->has(Func))
         return ConstantFoldFP(erf, APF, Ty);
       break;
+    case LibFunc_tgamma:
+    case LibFunc_tgammaf:
+      // NOTE: These boundaries are somewhat conservative.
+      if (TLI->has(Func) &&
+          (Ty->isDoubleTy() && APF > APFloat(DBL_MIN) && APF < APFloat(171.0) ||
+           Ty->isFloatTy() && APF > APFloat(FLT_MIN) && APF < APFloat(35.0f)))
+        return ConstantFoldFP(tgamma, APF, Ty);
+      break;
     case LibFunc_nearbyint:
     case LibFunc_nearbyintf:
     case LibFunc_rint:
@@ -3629,6 +3638,10 @@ bool llvm::isMathLibCallNoop(const CallBase *Call,
       case LibFunc_sqrtf:
         return Op.isNaN() || Op.isZero() || !Op.isNegative();
 
+      case LibFunc_tgamma:
+      case LibFunc_tgammaf:
+        return true;
+
       // FIXME: Add more functions: sqrt_finite, atanh, expm1, log1p,
       // maybe others?
       default: