[PATCH] D67300: [ConstantFolding] Fold constant calls to log2()

[Evandro Menezes via Phabricator via llvm-commits]

evandro created this revision.
evandro added reviewers: spatel, efriedma, xbolva00.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.
evandro added a parent revision: D67199: [InstCombine] Expand the simplification of log().

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


Repository:
  rL LLVM

https://reviews.llvm.org/D67300

Files:
  llvm/lib/Analysis/ConstantFolding.cpp
  llvm/test/Analysis/ConstantFolding/math-1.ll


Index: llvm/test/Analysis/ConstantFolding/math-1.ll
===================================================================
--- llvm/test/Analysis/ConstantFolding/math-1.ll
+++ llvm/test/Analysis/ConstantFolding/math-1.ll
@@ -92,14 +92,14 @@
   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 @@
   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
Index: llvm/lib/Analysis/ConstantFolding.cpp
===================================================================
--- llvm/lib/Analysis/ConstantFolding.cpp
+++ llvm/lib/Analysis/ConstantFolding.cpp
@@ -1490,6 +1490,7 @@
            Name == "fmod" || Name == "fmodf";
   case 'l':
     return Name == "log" || Name == "logf" ||
+           Name == "log2" || Name == "log2f" ||
            Name == "log10" || Name == "log10f";
   case 'p':
     return Name == "pow" || Name == "powf";
@@ -1868,6 +1869,13 @@
       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))
+        return ConstantFoldFP(Log2, V, Ty);
+      break;
     case LibFunc_log10:
     case LibFunc_log10f:
     case LibFunc_log10_finite:


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