[PowerPC] Make sure that we remove dead PHI nodes after the PPCCTRLoo…

…ps pass.

Commiting on behalf of Stefan Pintilie.
Differential Revision: https://reviews.llvm.org/D34829

llvm-svn: 307180

llvm/lib/Target/PowerPC/PPCCTRLoops.cpp

@@ -607,7 +607,10 @@ bool PPCCTRLoops::convertToCTRLoop(Loop *L) {
   // The old condition may be dead now, and may have even created a dead PHI
   // (the original induction variable).
   RecursivelyDeleteTriviallyDeadInstructions(OldCond);
-  DeleteDeadPHIs(CountedExitBlock);
+  // Run through the basic blocks of the loop and see if any of them have dead
+  // PHIs that can be removed.
+  for (auto I : L->blocks())
+    DeleteDeadPHIs(I);
 
   ++NumCTRLoops;
   return MadeChange;

llvm/test/CodeGen/PowerPC/ppc-ctr-dead-code.ll

@@ -0,0 +1,38 @@
+; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr9 -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr9 -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -mtriple=powerpc64le-unknown-linux-gnu -mcpu=pwr8 -verify-machineinstrs | FileCheck %s
+; RUN: llc < %s -mtriple=powerpc64-unknown-linux-gnu -mcpu=pwr8 -verify-machineinstrs | FileCheck %s
+
+; Function Attrs: norecurse nounwind readonly
+define signext i32 @limit_loop(i32 signext %iters, i32* nocapture readonly %vec, i32 signext %limit) local_unnamed_addr {
+entry:
+  %cmp5 = icmp sgt i32 %iters, 0
+  br i1 %cmp5, label %for.body.preheader, label %cleanup
+
+for.body.preheader:                               ; preds = %entry
+  %0 = sext i32 %iters to i64
+  br label %for.body
+
+for.cond:                                         ; preds = %for.body
+  %cmp = icmp slt i64 %indvars.iv.next, %0
+  br i1 %cmp, label %for.body, label %cleanup
+
+for.body:                                         ; preds = %for.body.preheader, %for.cond
+  %indvars.iv = phi i64 [ 0, %for.body.preheader ], [ %indvars.iv.next, %for.cond ]
+  %arrayidx = getelementptr inbounds i32, i32* %vec, i64 %indvars.iv
+  %1 = load i32, i32* %arrayidx, align 4
+  %cmp1 = icmp slt i32 %1, %limit
+  %indvars.iv.next = add nuw nsw i64 %indvars.iv, 1
+  br i1 %cmp1, label %for.cond, label %cleanup
+
+cleanup:                                          ; preds = %for.body, %for.cond, %entry
+  %2 = phi i32 [ 0, %entry ], [ 0, %for.cond ], [ 1, %for.body ]
+  ret i32 %2
+; CHECK-LABEL: limit_loop
+; CHECK: mtctr
+; CHECK-NOT: addi {{[0-9]+}}, {{[0-9]+}}, 1
+; CHECK: bdnz
+; CHECK: blr
+}
+
+