[PowerPC] Handle loop predecessor invokes

If a loop predecessor has an invoke as its terminator, and the return value
from that invoke is used to determine the loop iteration space, then we can't
insert a computation based on that value in the loop predecessor prior to the
terminator (oops). If there's such an invoke, or just no predecessor for that
matter, insert a new loop preheader.

llvm-svn: 228488

llvm/lib/Target/PowerPC/PPCLoopPreIncPrep.cpp

@@ -41,6 +41,7 @@
 #include "llvm/Support/Debug.h"
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/Local.h"
+#include "llvm/Transforms/Utils/LoopUtils.h"
 #include "llvm/Transforms/Utils/ValueMapper.h"
 using namespace llvm;
 
@@ -165,9 +166,6 @@ bool PPCLoopPreIncPrep::runOnLoop(Loop *L) {
     return MadeChange;
 
   BasicBlock *Header = L->getHeader();
-  BasicBlock *LoopPredecessor = L->getLoopPredecessor();
-  if (!LoopPredecessor)
-    return MadeChange;
 
   const PPCSubtarget *ST =
     TM ? TM->getSubtargetImpl(*Header->getParent()) : nullptr;
@@ -236,7 +234,17 @@ bool PPCLoopPreIncPrep::runOnLoop(Loop *L) {
     }
   }
 
-  if (Buckets.size() > MaxVars)
+  if (Buckets.empty() || Buckets.size() > MaxVars)
+    return MadeChange;
+
+  BasicBlock *LoopPredecessor = L->getLoopPredecessor();
+  // If there is no loop predecessor, or the loop predecessor's terminator
+  // returns a value (which might contribute to determining the loop's
+  // iteration space), insert a new preheader for the loop.
+  if (!LoopPredecessor ||
+      !LoopPredecessor->getTerminator()->getType()->isVoidTy())
+    LoopPredecessor = InsertPreheaderForLoop(L, this);
+  if (!LoopPredecessor)
     return MadeChange;
 
   SmallSet<BasicBlock *, 16> BBChanged;

llvm/test/CodeGen/PowerPC/preincprep-invoke.ll

@@ -0,0 +1,50 @@
+; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+@.str1 = external unnamed_addr constant [1 x i8], align 1
+@.str2 = external unnamed_addr constant [39 x i8], align 1
+
+declare void @_ZN13CStdOutStreamlsEPKc()
+
+declare void @_ZN13CStdOutStream5FlushEv()
+
+declare i32 @__gxx_personality_v0(...)
+
+define void @_Z11GetPasswordP13CStdOutStreamb() {
+entry:
+  br label %for.cond.i.i
+
+for.cond.i.i:                                     ; preds = %for.cond.i.i, %entry
+  br i1 undef, label %_ZN11CStringBaseIcEC2EPKc.exit.critedge, label %for.cond.i.i
+
+_ZN11CStringBaseIcEC2EPKc.exit.critedge:          ; preds = %for.cond.i.i
+  invoke void @_ZN13CStdOutStreamlsEPKc()
+          to label %invoke.cont unwind label %lpad
+
+invoke.cont:                                      ; preds = %_ZN11CStringBaseIcEC2EPKc.exit.critedge
+  invoke void @_ZN13CStdOutStream5FlushEv()
+          to label %invoke.cont4 unwind label %lpad
+
+invoke.cont4:                                     ; preds = %invoke.cont
+  %call7 = invoke i8* @getpass()
+          to label %for.cond.i.i30 unwind label %lpad
+
+; CHECK-LABEL: @_Z11GetPasswordP13CStdOutStreamb
+; CHECK: addi {{[0-9]+}}, 3, -1
+
+for.cond.i.i30:                                   ; preds = %for.cond.i.i30, %invoke.cont4
+  %indvars.iv.i.i26 = phi i64 [ %indvars.iv.next.i.i29, %for.cond.i.i30 ], [ 0, %invoke.cont4 ]
+  %arrayidx.i.i27 = getelementptr inbounds i8* %call7, i64 %indvars.iv.i.i26
+  %0 = load i8* %arrayidx.i.i27, align 1
+  %indvars.iv.next.i.i29 = add nuw nsw i64 %indvars.iv.i.i26, 1
+  br label %for.cond.i.i30
+
+lpad:                                             ; preds = %invoke.cont4, %invoke.cont, %_ZN11CStringBaseIcEC2EPKc.exit.critedge
+  %1 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          cleanup
+  resume { i8*, i32 } undef
+}
+
+declare i8* @getpass()
+