[ConstantFolding] Fold constant calls to log2()

Somehow, folding calls to `log2()` with a constant was missing.

Differential revision: https://reviews.llvm.org/D67300

llvm-svn: 373262

diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index f8ea8cf..8dbcf70 100644 (file)
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -1508,6 +1508,7 @@ bool llvm::canConstantFoldCallTo(const CallBase *Call, const Function *F) {
            Name == "fmod" || Name == "fmodf";
   case 'l':
     return Name == "log" || Name == "logf" ||
+           Name == "log2" || Name == "log2f" ||
            Name == "log10" || Name == "log10f";
   case 'n':
     return Name == "nearbyint" || Name == "nearbyintf";
@@ -1890,6 +1891,14 @@ static Constant *ConstantFoldScalarCall1(StringRef Name,
       if (V > 0.0 && TLI->has(Func))
         return ConstantFoldFP(log, V, Ty);
       break;
+    case LibFunc_log2:
+    case LibFunc_log2f:
+    case LibFunc_log2_finite:
+    case LibFunc_log2f_finite:
+      if (V > 0.0 && TLI->has(Func))
+        // TODO: What about hosts that lack a C99 library?
+        return ConstantFoldFP(Log2, V, Ty);
+      break;
     case LibFunc_log10:
     case LibFunc_log10f:
     case LibFunc_log10_finite:

diff --git a/llvm/test/Analysis/ConstantFolding/math-1.ll b/llvm/test/Analysis/ConstantFolding/math-1.ll
index 1733207..5950950 100644 (file)
--- a/llvm/test/Analysis/ConstantFolding/math-1.ll
+++ b/llvm/test/Analysis/ConstantFolding/math-1.ll
@@ -92,14 +92,14 @@ define double @i_exp2() {
   ret double %res
 }
 
-; FIXME
+; FIXME: exp10() is not widely supported.
 declare float @exp10f(float)
 define float @f_exp10f() {
 ; CHECK-LABEL: @f_exp10f(
-; CHECK-NEXT:    [[RES:%.*]] = tail call fast float @exp10f(float 1.000000e+00)
+; CHECK-NEXT:    [[RES:%.*]] = tail call float @exp10f(float 1.000000e+00)
 ; CHECK-NEXT:    ret float [[RES]]
 ;
-  %res = tail call fast float @exp10f(float 1.0)
+  %res = tail call float @exp10f(float 1.0)
   ret float %res
 }
 
@@ -121,12 +121,10 @@ define double @i_log() {
   ret double %res
 }
 
-; FIXME
 declare float @log2f(float)
 define float @f_log2f() {
 ; CHECK-LABEL: @f_log2f(
-; CHECK-NEXT:    [[RES:%.*]] = tail call fast float @log2f(float 1.000000e+00)
-; CHECK-NEXT:    ret float [[RES]]
+; CHECK-NEXT:    ret float 0.000000e+00
 ;
   %res = tail call fast float @log2f(float 1.0)
   ret float %res