[PATCH] [IfCvt] Don't re-ifconvert blocks with unanalyzable terminators.

[Ahmed Bougacha]

REPOSITORY
  rL LLVM

http://reviews.llvm.org/D8509

Files:
  llvm/trunk/lib/CodeGen/IfConversion.cpp
  llvm/trunk/test/CodeGen/ARM/ifcvt-iter-indbr.ll

Index: llvm/trunk/lib/CodeGen/IfConversion.cpp
===================================================================
--- llvm/trunk/lib/CodeGen/IfConversion.cpp
+++ llvm/trunk/lib/CodeGen/IfConversion.cpp
@@ -726,6 +726,12 @@
   if (BBI.IsDone || BBI.IsUnpredicable)
     return false;
 
+  // If it is already predicated but we couldn't analyze its terminator, the
+  // latter might fallthrough, but we can't determine where to.
+  // Conservatively avoid if-converting again.
+  if (BBI.Predicate.size() && !BBI.IsBrAnalyzable)
+    return false;
+
   // If it is already predicated, check if the new predicate subsumes
   // its predicate.
   if (BBI.Predicate.size() && !TII->SubsumesPredicate(Pred, BBI.Predicate))
Index: llvm/trunk/test/CodeGen/ARM/ifcvt-iter-indbr.ll
===================================================================
--- llvm/trunk/test/CodeGen/ARM/ifcvt-iter-indbr.ll
+++ llvm/trunk/test/CodeGen/ARM/ifcvt-iter-indbr.ll
@@ -0,0 +1,56 @@
+; RUN: llc < %s -mtriple thumbv7s-apple-darwin  -asm-verbose=false | FileCheck %s
+
+declare i32 @foo(i32)
+declare i8* @bar(i32, i8*, i8*)
+
+; Verify that we don't try to iteratively re-ifconvert a block with a
+; (predicated) indirectbr terminator.
+; If we do, we would ignore its fallthrough successor.
+
+
+; CHECK-LABEL: test:
+; CHECK:       cmp {{.*}}, #21
+; CHECK-NEXT:  itt eq
+; CHECK-NEXT:  streq.w
+; CHECK-NEXT:  moveq pc
+; CHECK-NEXT: LBB{{[0-9_]+}}:
+; CHECK-NEXT:  cmp {{.*}}, #42
+; CHECK-NEXT:  itt ne
+; CHECK-NEXT:  strne.w
+; CHECK-NEXT:  movne pc
+; CHECK-NEXT: Ltmp
+; CHECK-NEXT: LBB0_2:
+; CHECK-NEXT:  movw r0, #1234
+; CHECK-NEXT:  b [[FOOCALL:LBB[0-9_]+]]
+; CHECK-NEXT: Ltmp
+; CHECK-NEXT: LBB{{[0-9_]+}}:
+; CHECK-NEXT:  movw r0, #4567
+; CHECK-NEXT: [[FOOCALL]]:
+; CHECK-NEXT:  blx _foo
+
+define i32 @test(i32 %a, i32 %a2, i32* %p, i32* %p2) {
+entry:
+  %dst1 = call i8* @bar(i32 1, i8* blockaddress(@test, %bb1), i8* blockaddress(@test, %bb2))
+  %dst2 = call i8* @bar(i32 2, i8* blockaddress(@test, %bb1), i8* blockaddress(@test, %bb2))
+  %dst3 = call i8* @bar(i32 3, i8* blockaddress(@test, %bb1), i8* blockaddress(@test, %bb2))
+  %cc1 = icmp eq i32 %a, 21
+  br i1 %cc1, label %cc1t, label %cc1f
+
+cc1t:
+  store i32 %a, i32* %p
+  indirectbr i8* %dst3, [label %bb1, label %bb2]
+
+cc1f:
+  %cc2 = icmp ne i32 %a2, 42
+  br i1 %cc2, label %cc2t, label %bb1
+cc2t:
+  store i32 %a, i32* %p2
+  indirectbr i8* %dst1, [label %bb1, label %bb2]
+
+bb1:
+  %ret_bb1 = call i32 @foo(i32 1234)
+  ret i32 %ret_bb1
+bb2:
+  %ret_bb2 = call i32 @foo(i32 4567)
+  ret i32 %ret_bb2
+}

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