From c840da14c61ef336a530af8811a7268fccf3bd75 Mon Sep 17 00:00:00 2001
From: Devang Patel <dpatel@apple.com>
Date: Tue, 29 Jan 2008 02:20:41 +0000
Subject: [PATCH] Filter loops that subtract induction variables. These loops
 are not yet handled.

Fix PR 1912.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@46484 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/LoopIndexSplit.cpp      | 34 +++++++-------
 .../LoopIndexSplit/2008-01-28-IndDecrement.ll | 46 +++++++++++++++++++
 2 files changed, 63 insertions(+), 17 deletions(-)
 create mode 100644 test/Transforms/LoopIndexSplit/2008-01-28-IndDecrement.ll

diff --git a/lib/Transforms/Scalar/LoopIndexSplit.cpp b/lib/Transforms/Scalar/LoopIndexSplit.cpp
index 6698d67f91e..d31a589a78e 100644
--- a/lib/Transforms/Scalar/LoopIndexSplit.cpp
+++ b/lib/Transforms/Scalar/LoopIndexSplit.cpp
@@ -301,23 +301,23 @@ void LoopIndexSplit::findIndVar(Value *V, Loop *L) {
   Value *Op0 = I->getOperand(0);
   Value *Op1 = I->getOperand(1);
   
-  if (PHINode *PN = dyn_cast<PHINode>(Op0)) {
-    if (PN->getParent() == L->getHeader()
-        && isa<ConstantInt>(Op1)) {
-      IndVar = PN;
-      IndVarIncrement = I;
-      return;
-    }
-  }
-  
-  if (PHINode *PN = dyn_cast<PHINode>(Op1)) {
-    if (PN->getParent() == L->getHeader()
-        && isa<ConstantInt>(Op0)) {
-      IndVar = PN;
-      IndVarIncrement = I;
-      return;
-    }
-  }
+  if (PHINode *PN = dyn_cast<PHINode>(Op0)) 
+    if (PN->getParent() == L->getHeader()) 
+      if (ConstantInt *CI = dyn_cast<ConstantInt>(Op1)) 
+        if (CI->isOne()) {
+          IndVar = PN;
+          IndVarIncrement = I;
+          return;
+        }
+
+  if (PHINode *PN = dyn_cast<PHINode>(Op1)) 
+    if (PN->getParent() == L->getHeader()) 
+      if (ConstantInt *CI = dyn_cast<ConstantInt>(Op0)) 
+        if (CI->isOne()) {
+          IndVar = PN;
+          IndVarIncrement = I;
+          return;
+        }
   
   return;
 }
diff --git a/test/Transforms/LoopIndexSplit/2008-01-28-IndDecrement.ll b/test/Transforms/LoopIndexSplit/2008-01-28-IndDecrement.ll
new file mode 100644
index 00000000000..a4966a9de4a
--- /dev/null
+++ b/test/Transforms/LoopIndexSplit/2008-01-28-IndDecrement.ll
@@ -0,0 +1,46 @@
+; RUN: llvm-as < %s | opt -loop-index-split -disable-output -stats |& \
+; RUN: not grep "loop-index-split" 
+
+; Induction variable decrement is not yet handled.
+; pr1912.bc
+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 = "i686-apple-darwin9"
+	%struct.cset = type { i8*, i8, i8, i32, i8* }
+	%struct.parse = type { i8*, i8*, i32, i32*, i32, i32, i32, %struct.re_guts*, [10 x i32], [10 x i32] }
+	%struct.re_guts = type { i32, i32*, i32, i32, %struct.cset*, i8*, i32, i32, i32, i32, i32, i32, i32, i32, i8*, i8*, i32, i32, i32, i32, [1 x i8] }
+
+define fastcc void @p_bracket(%struct.parse* %p) {
+entry:
+	br i1 false, label %bb160, label %bb195
+
+bb160:		; preds = %entry
+	br i1 false, label %bb.i169, label %bb9.i
+
+bb195:		; preds = %entry
+	ret void
+
+bb.i169:		; preds = %bb160
+	br i1 false, label %bb372, label %bb565
+
+bb9.i:		; preds = %bb160
+	ret void
+
+bb372:		; preds = %bb418, %bb.i169
+	%i1.0.reg2mem.0 = phi i32 [ %i1.0, %bb418 ], [ 0, %bb.i169 ]		; <i32> [#uses=2]
+	%tmp3.i.i.i170 = icmp ult i32 %i1.0.reg2mem.0, 128		; <i1> [#uses=1]
+	br i1 %tmp3.i.i.i170, label %bb.i.i173, label %bb13.i.i
+
+bb.i.i173:		; preds = %bb372
+	br label %bb418
+
+bb13.i.i:		; preds = %bb372
+	br label %bb418
+
+bb418:		; preds = %bb13.i.i, %bb.i.i173
+	%i1.0 = add i32 %i1.0.reg2mem.0, -1		; <i32> [#uses=2]
+	%tmp420 = icmp sgt i32 %i1.0, -1		; <i1> [#uses=1]
+	br i1 %tmp420, label %bb372, label %bb565
+
+bb565:		; preds = %bb418, %bb.i169
+	ret void
+}
-- 
2.34.1