[LibCallSimplifier] don't allow sqrt transform unless all ops are unsafe

rotateright · rotateright · commit 6c1ddbb7b6ee · 2016-01-11T22:50:36.000Z
Fix the FIXME added with: http://reviews.llvm.org/rL257400 llvm-svn: 257404
diff --git a/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp b/llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp
@@ -1422,10 +1422,10 @@ Value *LibCallSimplifier::optimizeSqrt(CallInst *CI, IRBuilder<> &B) {
     // variations of this pattern because instcombine's visitFMUL and/or the
     // reassociation pass should give us this form.
     Value *OtherMul0, *OtherMul1;
-    // FIXME: This multiply must be unsafe to allow this transform.
     if (match(Op0, m_FMul(m_Value(OtherMul0), m_Value(OtherMul1)))) {
       // Pattern: sqrt((x * y) * z)
-      if (OtherMul0 == OtherMul1) {
+      if (OtherMul0 == OtherMul1 &&
+          cast<Instruction>(Op0)->hasUnsafeAlgebra()) {
         // Matched: sqrt((x * x) * z)
         RepeatOp = OtherMul0;
         OtherOp = Op1;
diff --git a/llvm/test/Transforms/InstCombine/fast-math.ll b/llvm/test/Transforms/InstCombine/fast-math.ll
@@ -649,6 +649,21 @@ define double @sqrt_intrinsic_three_args6(double %x, double %y) {
 ; CHECK-NEXT: ret double %1
 }
 
+; If any operation is not 'fast', we can't simplify.
+
+define double @sqrt_intrinsic_not_so_fast(double %x, double %y) {
+  %mul = fmul double %x, %x
+  %mul2 = fmul fast double %mul, %y
+  %sqrt = call fast double @llvm.sqrt.f64(double %mul2)
+  ret double %sqrt
+
+; CHECK-LABEL: sqrt_intrinsic_not_so_fast(
+; CHECK-NEXT:  %mul = fmul double %x, %x
+; CHECK-NEXT:  %mul2 = fmul fast double %mul, %y
+; CHECK-NEXT:  %sqrt = call fast double @llvm.sqrt.f64(double %mul2)
+; CHECK-NEXT:  ret double %sqrt
+}
+
 define double @sqrt_intrinsic_arg_4th(double %x) {
   %mul = fmul fast double %x, %x
   %mul2 = fmul fast double %mul, %mul
