for (MachineBasicBlock::reverse_iterator I = MBB->rbegin(), E = MBB->rend();
I != E; ++I) {
+ // Update liveness, including the current instrucion's defs.
+ LiveUnits.stepBackward(*I, *TRI);
+
if (UndefMI == &*I) {
if (!LiveUnits.contains(UndefMI->getOperand(OpIdx).getReg(), *TRI))
TII->breakPartialRegDependency(UndefMI, OpIdx, TRI);
UndefMI = UndefReads.back().first;
OpIdx = UndefReads.back().second;
}
- LiveUnits.stepBackward(*I, *TRI);
}
}
--- /dev/null
+; 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
+}