[llvm] r257404 - [LibCallSimplifier] don't allow sqrt transform unless all ops are unsafe

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon Jan 11 16:50:36 2016
New Revision: 257404

URL: http://llvm.org/viewvc/llvm-project?rev=257404&view=rev
Log:
[LibCallSimplifier] don't allow sqrt transform unless all ops are unsafe

Fix the FIXME added with:
http://reviews.llvm.org/rL257400


Modified:
    llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
    llvm/trunk/test/Transforms/InstCombine/fast-math.ll

Modified: llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp?rev=257404&r1=257403&r2=257404&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyLibCalls.cpp Mon Jan 11 16:50:36 2016
@@ -1422,10 +1422,10 @@ Value *LibCallSimplifier::optimizeSqrt(C
     // 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;

Modified: llvm/trunk/test/Transforms/InstCombine/fast-math.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fast-math.ll?rev=257404&r1=257403&r2=257404&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fast-math.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/fast-math.ll Mon Jan 11 16:50:36 2016
@@ -649,6 +649,21 @@ define double @sqrt_intrinsic_three_args
 ; 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