Optimize square root squared (PR21126).
When unsafe-fp-math is enabled, we can turn sqrt(X) * sqrt(X) into X.
This can happen in the real world when calculating x ** 3/2. This occurs
in test-suite/SingleSource/Benchmarks/BenchmarkGame/n-body.c.
Differential Revision: http://reviews.llvm.org/D5584
llvm-svn: 218906
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
index da5d00d..0a19a48 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -531,6 +531,11 @@
}
}
+ // sqrt(X) * sqrt(X) -> X
+ if (AllowReassociate && (Op0 == Op1))
+ if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Op0))
+ if (II->getIntrinsicID() == Intrinsic::sqrt)
+ return ReplaceInstUsesWith(I, II->getOperand(0));
// Under unsafe algebra do:
// X * log2(0.5*Y) = X*log2(Y) - X