1 files changed, 29 insertions, 0 deletions
diff --git a/test/CodeGen/X86/break-avx-dep.ll b/test/CodeGen/X86/break-avx-dep.ll
new file mode 100644
index 0000000000..eea7d1565d
--- /dev/null
+++ b/test/CodeGen/X86/break-avx-dep.ll
@@ -0,0 +1,29 @@
+; RUN: llc < %s -march=x86-64 -mattr=+avx | FileCheck %s
+;
+; rdar:15221834 False AVX register dependencies cause 5x slowdown on
+; flops-6. Make sure the unused register read by vcvtsi2sdq is zeroed
+; to avoid cyclic dependence on a write to the same register in a
+; previous iteration.
+
+; CHECK-LABEL: t1:
+; CHECK-LABEL: %loop
+; CHECK: vxorps %[[REG:xmm.]], %{{xmm.}}, %{{xmm.}}
+; CHECK: vcvtsi2sdq %{{r..}}, %[[REG]], %{{xmm.}}
+define i64 @t1(i64* nocapture %x, double* nocapture %y) nounwind {
+entry:
+  %vx = load i64* %x
+  br label %loop
+loop:
+  %i = phi i64 [ 1, %entry ], [ %inc, %loop ]
+  %s1 = phi i64 [ %vx, %entry ], [ %s2, %loop ]
+  %fi = sitofp i64 %i to double
+  %vy = load double* %y
+  %fipy = fadd double %fi, %vy
+  %iipy = fptosi double %fipy to i64
+  %s2 = add i64 %s1, %iipy
+  %inc = add nsw i64 %i, 1
+  %exitcond = icmp eq i64 %inc, 156250000
+  br i1 %exitcond, label %ret, label %loop
+ret:
+  ret i64 %s2
+}