[PowerPC] Mark the BDNZ intrinsic as NoDuplicate

Duplicating this intrinsic is not generally valid because it has the side-effect
of decrementing the CTR. Any passes that duplicate it would need to be taught to
keep the regions formed completely disjoint.
This patch should be NFC for typical uses as CTRLoops runs after the remaining
loop passes. It only affects situations where the loop passes are scheduled on
the IR after the codegen passes (as is the case with some JIT pipelines).

Fixes https://bugs.llvm.org/show_bug.cgi?id=37050

llvm-svn: 330186

llvm/include/llvm/IR/IntrinsicsPowerPC.td

@@ -36,8 +36,12 @@ let TargetPrefix = "ppc" in {  // All intrinsics start with "llvm.ppc.".
 
   // Intrinsics used to generate ctr-based loops. These should only be
   // generated by the PowerPC backend!
+  // The branch intrinsic is marked as NoDuplicate because loop rotation will
+  // attempt to duplicate it forming loops where a block reachable from one
+  // instance of it can contain another.
   def int_ppc_mtctr : Intrinsic<[], [llvm_anyint_ty], []>;
-  def int_ppc_is_decremented_ctr_nonzero : Intrinsic<[llvm_i1_ty], [], []>;
+  def int_ppc_is_decremented_ctr_nonzero :
+    Intrinsic<[llvm_i1_ty], [], [IntrNoDuplicate]>;
 
   // Intrinsics for [double]word extended forms of divide instructions
   def int_ppc_divwe : GCCBuiltin<"__builtin_divwe">,

llvm/test/CodeGen/PowerPC/no-dup-of-bdnz.ll

@@ -0,0 +1,75 @@
+; RUN: opt -early-cse-memssa -loop-rotate -licm -loop-rotate -S %s -o - | FileCheck %s
+; ModuleID = 'bugpoint-reduced-simplified.bc'
+source_filename = "bugpoint-output-8903f29.bc"
+target datalayout = "e-m:e-i64:64-n32:64"
+target triple = "powerpc64le-unknown-linux-gnu"
+
+define void @test(i64 %arg.ssa, i64 %arg.nb) local_unnamed_addr {
+; Ensure that loop rotation doesn't duplicate the call to
+; llvm.ppc.is.decremented.ctr.nonzero
+; CHECK-LABEL: test
+; CHECK: call i1 @llvm.ppc.is.decremented.ctr.nonzero
+; CHECK-NOT: call i1 @llvm.ppc.is.decremented.ctr.nonzero
+; CHECK: declare i1 @llvm.ppc.is.decremented.ctr.nonzero
+entry:
+  switch i32 undef, label %BB_8 [
+    i32 -2, label %BB_9
+    i32 0, label %BB_9
+  ]
+
+BB_1:                                    ; preds = %BB_12, %BB_4
+  %bcount.1.us = phi i64 [ %.810.us, %BB_4 ], [ 0, %BB_12 ]
+  %0 = add i64 %arg.ssa, %bcount.1.us
+  %.568.us = load i32, i32* undef, align 4
+  %.15.i.us = icmp slt i32 0, %.568.us
+  br i1 %.15.i.us, label %BB_3, label %BB_2
+
+BB_2:                                          ; preds = %BB_1
+  %.982.us = add nsw i64 %0, 1
+  unreachable
+
+BB_3:                                          ; preds = %BB_1
+  %1 = add i64 %arg.ssa, %bcount.1.us
+  %2 = add i64 %1, 1
+  %3 = call i1 @llvm.ppc.is.decremented.ctr.nonzero()
+  br i1 %3, label %BB_4, label %BB_7
+
+BB_4:                                          ; preds = %BB_3
+  %.810.us = add nuw nsw i64 %bcount.1.us, 1
+  br label %BB_1
+
+BB_5:                                         ; preds = %BB_7, %BB_5
+  %lsr.iv20.i116 = phi i64 [ %2, %BB_7 ], [ %lsr.iv.next21.i126, %BB_5 ]
+  %lsr.iv.next21.i126 = add i64 %lsr.iv20.i116, 1
+  br i1 undef, label %BB_5, label %BB_6
+
+BB_6:                                         ; preds = %BB_5
+  ret void
+
+BB_7:                                     ; preds = %BB_3
+  br label %BB_5
+
+BB_8:                                           ; preds = %entry
+  ret void
+
+BB_9:                                        ; preds = %entry, %entry
+  br label %BB_10
+
+BB_10:                               ; preds = %BB_9
+  br label %BB_11
+
+BB_11:                                         ; preds = %BB_11, %BB_10
+  br i1 undef, label %BB_11, label %BB_12
+
+BB_12:                                         ; preds = %BB_11
+  call void @llvm.ppc.mtctr.i64(i64 %arg.nb)
+  br label %BB_1
+}
+
+; Function Attrs: nounwind
+declare void @llvm.ppc.mtctr.i64(i64) #0
+
+; Function Attrs: nounwind
+declare i1 @llvm.ppc.is.decremented.ctr.nonzero() #0
+
+attributes #0 = { nounwind }