From 76f497a351c562f366b5e93c27d3f1652fb48ff4 Mon Sep 17 00:00:00 2001
From: Dan Gohman <gohman@apple.com>
Date: Tue, 25 Aug 2009 17:42:10 +0000
Subject: [PATCH] Special-case static allocas in IndVarSimplify's loop
 invariant sinking code, since they are special. If the loop preheader happens
 to be the entry block of a function, don't sink static allocas out of it.
 This fixes PR4775.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@80010 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Transforms/Scalar/IndVarSimplify.cpp      |  5 +++
 test/Transforms/IndVarSimplify/sink-alloca.ll | 31 +++++++++++++++++++
 2 files changed, 36 insertions(+)
 create mode 100644 test/Transforms/IndVarSimplify/sink-alloca.ll

diff --git a/lib/Transforms/Scalar/IndVarSimplify.cpp b/lib/Transforms/Scalar/IndVarSimplify.cpp
index 790a4fc51d2..ceca45220e9 100644
--- a/lib/Transforms/Scalar/IndVarSimplify.cpp
+++ b/lib/Transforms/Scalar/IndVarSimplify.cpp
@@ -553,6 +553,11 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
     // dominates the exit block.
     if (I->mayHaveSideEffects() || I->mayReadFromMemory())
       continue;
+    // Don't sink static AllocaInsts out of the entry block, which would
+    // turn them into dynamic allocas!
+    if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
+      if (AI->isStaticAlloca())
+        continue;
     // Determine if there is a use in or before the loop (direct or
     // otherwise).
     bool UsedInLoop = false;
diff --git a/test/Transforms/IndVarSimplify/sink-alloca.ll b/test/Transforms/IndVarSimplify/sink-alloca.ll
new file mode 100644
index 00000000000..f5378ccea0b
--- /dev/null
+++ b/test/Transforms/IndVarSimplify/sink-alloca.ll
@@ -0,0 +1,31 @@
+; RUN: llvm-as < %s | opt -indvars | llvm-dis | FileCheck %s
+; PR4775
+
+; Indvars shouldn't sink the alloca out of the entry block, even though
+; it's not used until after the loop.
+
+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-darwin10.0"
+
+@llvm.used = appending global [1 x i8*] [i8* bitcast (i32 ()* @main to i8*)],
+section "llvm.metadata" ; <[1 x i8*]*> [#uses=0]
+
+define i32 @main() nounwind {
+; CHECK: entry:
+; CHECK-NEXT: %result.i = alloca i32, align 4
+entry:
+  %result.i = alloca i32, align 4                 ; <i32*> [#uses=2]
+  br label %while.cond
+
+while.cond:                                       ; preds = %while.cond, %entry
+  %call = call i32 @bar() nounwind                ; <i32> [#uses=1]
+  %tobool = icmp eq i32 %call, 0                  ; <i1> [#uses=1]
+  br i1 %tobool, label %while.end, label %while.cond
+
+while.end:                                        ; preds = %while.cond
+  volatile store i32 0, i32* %result.i
+  %tmp.i = volatile load i32* %result.i           ; <i32> [#uses=0]
+  ret i32 0
+}
+
+declare i32 @bar()