[llvm-commits] [llvm] r49458 - /llvm/trunk/lib/Transforms/IPO/SimplifyLibCalls.cpp

[Chris Lattner]

Author: lattner
Date: Wed Apr  9 21:07:51 2008
New Revision: 49458

URL: http://llvm.org/viewvc/llvm-project?rev=49458&view=rev
Log:
Disable an xform we've had for a long time, pow(x,0.5) -> sqrt.
This is not safe for all inputs.

Modified:
    llvm/trunk/lib/Transforms/IPO/SimplifyLibCalls.cpp

Modified: llvm/trunk/lib/Transforms/IPO/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/IPO/SimplifyLibCalls.cpp?rev=49458&r1=49457&r2=49458&view=diff

==============================================================================
--- llvm/trunk/lib/Transforms/IPO/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/IPO/SimplifyLibCalls.cpp Wed Apr  9 21:07:51 2008
@@ -1179,9 +1179,17 @@
       // pow(x, 0.0) -> 1.0
       return ReplaceCallWith(CI, ConstantFP::get(CI->getType(), 1.0));
     } else if (Op2C->isExactlyValue(0.5)) {
+      // FIXME: This is not safe for -0.0 and -inf.  This can only be done when
+      // 'unsafe' math optimizations are allowed.
+      // x    pow(x, 0.5)  sqrt(x)
+      // ---------------------------------------------
+      // -0.0    +0.0       -0.0
+      // -inf    +inf       NaN
+#if 0
       // pow(x, 0.5) -> sqrt(x)
       Value *Sqrt = CallInst::Create(SLC.get_sqrt(), Op1, "sqrt", CI);
       return ReplaceCallWith(CI, Sqrt);
+#endif
     } else if (Op2C->isExactlyValue(1.0)) {
       // pow(x, 1.0) -> x
       return ReplaceCallWith(CI, Op1);