From 73b52018e9c1b7fab10fb3f807a90ce0272c9092 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Wed, 25 Jun 2008 05:59:28 +0000
Subject: [PATCH] Fix PR2488, a case where we deleted stack restores too
 aggressively.

llvm-svn: 52702
---
 .../Scalar/InstructionCombining.cpp           | 13 +++++--
 .../InstCombine/2008-06-24-StackRestore.ll    | 39 +++++++++++++++++++
 2 files changed, 48 insertions(+), 4 deletions(-)
 create mode 100644 test/Transforms/InstCombine/2008-06-24-StackRestore.ll

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 37637bbe63b..d45eb99d939 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -8697,13 +8697,18 @@ Instruction *InstCombiner::visitCallInst(CallInst &CI) {
         CannotRemove = true;
         break;
       }
-      if (isa<CallInst>(BI)) {
-        if (!isa<IntrinsicInst>(BI)) {
+      if (CallInst *BCI = dyn_cast<CallInst>(BI)) {
+        if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BCI)) {
+          // If there is a stackrestore below this one, remove this one.
+          if (II->getIntrinsicID() == Intrinsic::stackrestore)
+            return EraseInstFromFunction(CI);
+          // Otherwise, ignore the intrinsic.
+        } else {
+          // If we found a non-intrinsic call, we can't remove the stack
+          // restore.
           CannotRemove = true;
           break;
         }
-        // If there is a stackrestore below this one, remove this one.
-        return EraseInstFromFunction(CI);
       }
     }
     
diff --git a/test/Transforms/InstCombine/2008-06-24-StackRestore.ll b/test/Transforms/InstCombine/2008-06-24-StackRestore.ll
new file mode 100644
index 00000000000..9ed7be38c6a
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-06-24-StackRestore.ll
@@ -0,0 +1,39 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {call.*llvm.stackrestore}
+; PR2488
+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-f80:32:32"
+target triple = "i386-pc-linux-gnu"
+@p = weak global i8* null		; <i8**> [#uses=2]
+
+define i32 @main() nounwind  {
+entry:
+	%tmp248 = call i8* @llvm.stacksave( )		; <i8*> [#uses=1]
+	%tmp2752 = alloca i32		; <i32*> [#uses=2]
+	%tmpcast53 = bitcast i32* %tmp2752 to i8*		; <i8*> [#uses=1]
+	store i32 2, i32* %tmp2752, align 4
+	volatile store i8* %tmpcast53, i8** @p, align 4
+	br label %bb44
+
+bb:		; preds = %bb44
+	ret i32 0
+
+bb44:		; preds = %bb44, %entry
+	%indvar = phi i32 [ 0, %entry ], [ %tmp3857, %bb44 ]		; <i32> [#uses=1]
+	%tmp249 = phi i8* [ %tmp248, %entry ], [ %tmp2, %bb44 ]		; <i8*> [#uses=1]
+	%tmp3857 = add i32 %indvar, 1		; <i32> [#uses=3]
+	call void @llvm.stackrestore( i8* %tmp249 )
+	%tmp2 = call i8* @llvm.stacksave( )		; <i8*> [#uses=1]
+	%tmp4 = srem i32 %tmp3857, 1000		; <i32> [#uses=2]
+	%tmp5 = add i32 %tmp4, 1		; <i32> [#uses=1]
+	%tmp27 = alloca i32, i32 %tmp5		; <i32*> [#uses=3]
+	%tmpcast = bitcast i32* %tmp27 to i8*		; <i8*> [#uses=1]
+	store i32 1, i32* %tmp27, align 4
+	%tmp34 = getelementptr i32* %tmp27, i32 %tmp4		; <i32*> [#uses=1]
+	store i32 2, i32* %tmp34, align 4
+	volatile store i8* %tmpcast, i8** @p, align 4
+	%exitcond = icmp eq i32 %tmp3857, 999999		; <i1> [#uses=1]
+	br i1 %exitcond, label %bb, label %bb44
+}
+
+declare i8* @llvm.stacksave() nounwind 
+
+declare void @llvm.stackrestore(i8*) nounwind