Don't infininitely thread branches when a threaded edge

goes back to the block, e.g.:

  Threading edge through bool from 'bb37.us.thread3829' to 'bb37.us' with cost: 1, across block:

bb37.us:		; preds = %bb37.us.thread3829, %bb37.us, %bb33
	%D1361.1.us = phi i32 [ %tmp36, %bb33 ], [ %D1361.1.us, %bb37.us ], [ 0, %bb37.us.thread3829 ]		; <i32> [#uses=2]
	%tmp39.us = icmp eq i32 %D1361.1.us, 0		; <i1> [#uses=1]
	br i1 %tmp39.us, label %bb37.us, label %bb42.us

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50251 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/JumpThreading.cpp b/lib/Transforms/Scalar/JumpThreading.cpp
index 92e40e66d4362eee1ee4d7154ee58465e8147a69..be94025404965347681827bc79b92d44d7a76e32 100644 (file)
--- a/lib/Transforms/Scalar/JumpThreading.cpp
+++ b/lib/Transforms/Scalar/JumpThreading.cpp
@@ -250,6 +250,13 @@ bool JumpThreading::ProcessJumpOnPHI(PHINode *PN) {
     SuccBB = SI->getSuccessor(SI->findCaseValue(PredCst));
   }
   
+  // If threading to the same block as we come from, we would infinite loop.
+  if (SuccBB == BB) {
+    DOUT << "  Not threading BB '" << BB->getNameStart()
+         << "' - would thread to self!\n";
+    return false;
+  }
+  
   // And finally, do it!
   DOUT << "  Threading edge from '" << PredBB->getNameStart() << "' to '"
        << SuccBB->getNameStart() << "' with cost: " << JumpThreadCost
@@ -319,6 +326,13 @@ bool JumpThreading::ProcessBranchOnLogical(Value *V, BasicBlock *BB,
   // 'true' block.
   BasicBlock *SuccBB = BB->getTerminator()->getSuccessor(isAnd);
   
+  // If threading to the same block as we come from, we would infinite loop.
+  if (SuccBB == BB) {
+    DOUT << "  Not threading BB '" << BB->getNameStart()
+    << "' - would thread to self!\n";
+    return false;
+  }
+  
   // And finally, do it!
   DOUT << "  Threading edge through bool from '" << PredBB->getNameStart()
        << "' to '" << SuccBB->getNameStart() << "' with cost: "
@@ -390,6 +404,14 @@ bool JumpThreading::ProcessBranchOnCompare(CmpInst *Cmp, BasicBlock *BB) {
   // Next, get our successor.
   BasicBlock *SuccBB = BB->getTerminator()->getSuccessor(!TrueDirection);
   
+  // If threading to the same block as we come from, we would infinite loop.
+  if (SuccBB == BB) {
+    DOUT << "  Not threading BB '" << BB->getNameStart()
+    << "' - would thread to self!\n";
+    return false;
+  }
+  
+  
   // And finally, do it!
   DOUT << "  Threading edge through bool from '" << PredBB->getNameStart()
        << "' to '" << SuccBB->getNameStart() << "' with cost: "

diff --git a/test/Transforms/JumpThreading/2008-04-24-InfLoop.ll b/test/Transforms/JumpThreading/2008-04-24-InfLoop.ll
new file mode 100644 (file)
index 0000000..3eb2aa1
--- /dev/null
+++ b/test/Transforms/JumpThreading/2008-04-24-InfLoop.ll
@@ -0,0 +1,142 @@
+; RUN: llvm-as < %s | opt -jump-threading -disable-output
+target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:32:64-f32:32:32-f64:32:64-v64:64:64-v128:128:128-a0:0:64-f80:128:128"
+target triple = "i386-apple-darwin9"
+@Link = global [1 x i32] [ i32 -1 ]            ; <[1 x i32]*> [#uses=2]
+@W = global [1 x i32] [ i32 2 ]                ; <[1 x i32]*> [#uses=1]
+
+define i32 @f(i32 %k, i32 %p) nounwind  {
+entry:
+       br label %bb
+
+bb:            ; preds = %bb56, %bb76.loopexit.us, %entry
+       %j.2 = phi i32 [ 0, %entry ], [ 1, %bb56 ], [ 1, %bb76.loopexit.us ]            ; <i32> [#uses=5]
+       %pdest.2 = phi i32 [ 0, %entry ], [ %pdest.8, %bb56 ], [ %pdest.7.us, %bb76.loopexit.us ]               ; <i32> [#uses=3]
+       %p_addr.0 = phi i32 [ %p, %entry ], [ 0, %bb56 ], [ %p_addr.1.us, %bb76.loopexit.us ]           ; <i32> [#uses=3]
+       %k_addr.0 = phi i32 [ %k, %entry ], [ %tmp59, %bb56 ], [ %tmp59.us, %bb76.loopexit.us ]         ; <i32> [#uses=4]
+       %tmp2 = icmp sgt i32 %pdest.2, 2                ; <i1> [#uses=1]
+       br i1 %tmp2, label %bb4.preheader, label %bb13
+
+bb4.preheader:         ; preds = %bb
+       %tmp109 = sub i32 1, %j.2               ; <i32> [#uses=2]
+       %tmp110 = icmp slt i32 %tmp109, -2              ; <i1> [#uses=1]
+       %smax111 = select i1 %tmp110, i32 -2, i32 %tmp109               ; <i32> [#uses=2]
+       %tmp112 = add i32 %j.2, %smax111                ; <i32> [#uses=2]
+       br label %bb4
+
+bb4:           ; preds = %bb4, %bb4.preheader
+       %indvar = phi i32 [ 0, %bb4.preheader ], [ %indvar.next, %bb4 ]         ; <i32> [#uses=1]
+       %indvar.next = add i32 %indvar, 1               ; <i32> [#uses=2]
+       %exitcond = icmp eq i32 %indvar.next, %tmp112           ; <i1> [#uses=1]
+       br i1 %exitcond, label %bb13.loopexit, label %bb4
+
+bb13.loopexit:         ; preds = %bb4
+       %tmp = add i32 %j.2, %pdest.2           ; <i32> [#uses=1]
+       %tmp102 = add i32 %tmp, %smax111                ; <i32> [#uses=1]
+       %tmp104 = add i32 %tmp112, -1           ; <i32> [#uses=1]
+       %tmp106 = sub i32 %j.2, %tmp104         ; <i32> [#uses=1]
+       %tmp107 = add i32 %tmp106, -1           ; <i32> [#uses=1]
+       br label %bb13
+
+bb13:          ; preds = %bb13.loopexit, %bb
+       %j.1 = phi i32 [ %tmp107, %bb13.loopexit ], [ %j.2, %bb ]               ; <i32> [#uses=4]
+       %pdest.1 = phi i32 [ %tmp102, %bb13.loopexit ], [ %pdest.2, %bb ]               ; <i32> [#uses=2]
+       %tmp15 = icmp eq i32 %j.1, 1            ; <i1> [#uses=1]
+       br i1 %tmp15, label %bb82, label %bb27.preheader
+
+bb27.preheader:                ; preds = %bb13
+       %tmp21 = icmp eq i32 %j.1, %p_addr.0            ; <i1> [#uses=0]
+       br label %bb27.outer
+
+bb27.outer:            ; preds = %bb27.outer.bb24.split_crit_edge, %bb27.preheader
+       %indvar118 = phi i32 [ 0, %bb27.preheader ], [ %indvar.next119, %bb27.outer.bb24.split_crit_edge ]              ; <i32> [#uses=2]
+       %pdest.3.ph = add i32 %indvar118, %pdest.1              ; <i32> [#uses=2]
+       %tmp30 = icmp sgt i32 %pdest.3.ph, %p_addr.0            ; <i1> [#uses=1]
+       br i1 %tmp30, label %bb27.outer.bb24.split_crit_edge, label %bb27.outer.split
+
+bb27.outer.bb24.split_crit_edge:               ; preds = %bb27.outer
+       %indvar.next119 = add i32 %indvar118, 1         ; <i32> [#uses=1]
+       br label %bb27.outer
+
+bb27.outer.split:              ; preds = %bb27.outer
+       %tmp35 = getelementptr [1 x i32]* @W, i32 0, i32 %k_addr.0              ; <i32*> [#uses=3]
+       %tmp48 = icmp slt i32 %p_addr.0, 1              ; <i1> [#uses=1]
+       %tmp53 = icmp sgt i32 %k_addr.0, 0              ; <i1> [#uses=1]
+       br label %bb33
+
+bb33:          ; preds = %bb51.split, %bb27.outer.split
+       %pdest.5 = phi i32 [ %pdest.3.ph, %bb27.outer.split ], [ %pdest.4, %bb51.split ]                ; <i32> [#uses=1]
+       %tmp36 = load i32* %tmp35, align 4              ; <i32> [#uses=2]
+       br i1 %tmp48, label %bb37.us, label %bb37
+
+bb37.us:               ; preds = %bb42.us, %bb37.us, %bb33
+       %D1361.1.us = phi i32 [ %tmp36, %bb33 ], [ 0, %bb42.us ], [ %D1361.1.us, %bb37.us ]             ; <i32> [#uses=2]
+       %tmp39.us = icmp eq i32 %D1361.1.us, 0          ; <i1> [#uses=1]
+       br i1 %tmp39.us, label %bb37.us, label %bb42.us
+
+bb42.us:               ; preds = %bb37.us
+       store i32 0, i32* %tmp35, align 4
+       br label %bb37.us
+
+bb37:          ; preds = %bb33
+       %tmp39 = icmp eq i32 %tmp36, 0          ; <i1> [#uses=1]
+       br i1 %tmp39, label %bb51.split, label %bb42
+
+bb42:          ; preds = %bb37
+       store i32 0, i32* %tmp35, align 4
+       br label %bb51.split
+
+bb51.split:            ; preds = %bb42, %bb37
+       %pdest.4 = phi i32 [ 1, %bb42 ], [ %pdest.5, %bb37 ]            ; <i32> [#uses=3]
+       br i1 %tmp53, label %bb33, label %bb56.preheader
+
+bb56.preheader:                ; preds = %bb51.split
+       %tmp7394 = icmp sgt i32 %j.1, 0         ; <i1> [#uses=1]
+       br i1 %tmp7394, label %bb56.us, label %bb56
+
+bb56.us:               ; preds = %bb76.loopexit.us, %bb56.preheader
+       %pdest.8.us = phi i32 [ %pdest.4, %bb56.preheader ], [ %pdest.7.us, %bb76.loopexit.us ]         ; <i32> [#uses=1]
+       %k_addr.1.us = phi i32 [ %k_addr.0, %bb56.preheader ], [ %tmp59.us, %bb76.loopexit.us ]         ; <i32> [#uses=1]
+       %tmp58.us = getelementptr [1 x i32]* @Link, i32 0, i32 %k_addr.1.us             ; <i32*> [#uses=1]
+       %tmp59.us = load i32* %tmp58.us, align 4                ; <i32> [#uses=3]
+       %tmp6295.us = icmp ne i32 %tmp59.us, -1         ; <i1> [#uses=2]
+       br label %bb60.us
+
+bb60.us:               ; preds = %bb60.us, %bb56.us
+       %pdest.7.reg2mem.0.us = phi i32 [ %pdest.8.us, %bb56.us ], [ %pdest.7.us, %bb60.us ]            ; <i32> [#uses=1]
+       %p_addr.1.reg2mem.0.us = phi i32 [ 0, %bb56.us ], [ %p_addr.1.us, %bb60.us ]            ; <i32> [#uses=1]
+       %tmp67.us = zext i1 %tmp6295.us to i32          ; <i32> [#uses=2]
+       %pdest.7.us = add i32 %pdest.7.reg2mem.0.us, %tmp67.us          ; <i32> [#uses=3]
+       %p_addr.1.us = add i32 %p_addr.1.reg2mem.0.us, %tmp67.us                ; <i32> [#uses=3]
+       %tmp73.us = icmp slt i32 %p_addr.1.us, %j.1             ; <i1> [#uses=1]
+       br i1 %tmp73.us, label %bb60.us, label %bb76.loopexit.us
+
+bb76.loopexit.us:              ; preds = %bb60.us
+       br i1 %tmp6295.us, label %bb56.us, label %bb
+
+bb56:          ; preds = %bb56, %bb56.preheader
+       %pdest.8 = phi i32 [ %pdest.4, %bb56.preheader ], [ %pdest.8, %bb56 ]           ; <i32> [#uses=2]
+       %k_addr.1 = phi i32 [ %k_addr.0, %bb56.preheader ], [ %tmp59, %bb56 ]           ; <i32> [#uses=1]
+       %tmp58 = getelementptr [1 x i32]* @Link, i32 0, i32 %k_addr.1           ; <i32*> [#uses=1]
+       %tmp59 = load i32* %tmp58, align 4              ; <i32> [#uses=3]
+       %tmp6295 = icmp ne i32 %tmp59, -1               ; <i1> [#uses=1]
+       br i1 %tmp6295, label %bb56, label %bb
+
+bb82:          ; preds = %bb13
+       ret i32 %pdest.1
+}
+
+define i32 @main() nounwind  {
+entry:
+       %tmp1 = tail call i32 @f( i32 0, i32 2 ) nounwind               ; <i32> [#uses=1]
+       %tmp2 = icmp eq i32 %tmp1, 0            ; <i1> [#uses=1]
+       br i1 %tmp2, label %bb, label %bb4
+
+bb:            ; preds = %entry
+       tail call void @abort( ) noreturn nounwind 
+       unreachable
+
+bb4:           ; preds = %entry
+       ret i32 0
+}
+
+declare void @abort() noreturn nounwind