It is not safe to sink an alloca into a stacksave/stackrestore pair, so don't do that. <rdar://problem/10352360>

llvm-svn: 143093

lib/Transforms/Scalar/IndVarSimplify.cpp

@@ -1680,11 +1680,12 @@ void IndVarSimplify::SinkUnusedInvariants(Loop *L) {
     if (isa<LandingPadInst>(I))
       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;
+    // Don't sink alloca: we never want to sink static alloca's out of the
+    // entry block, and correctly sinking dynamic alloca's requires
+    // checks for stacksave/stackrestore intrinsics.
+    // FIXME: Refactor this check somehow?
+    if (isa<AllocaInst>(I))
+      continue;
 
     // Determine if there is a use in or before the loop (direct or
     // otherwise).

test/Transforms/IndVarSimplify/sink-alloca.ll

@@ -1,15 +1,10 @@
 ; RUN: opt < %s -indvars -S | 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]
-
+; PR4775
+; Indvars shouldn't sink the alloca out of the entry block, even though
+; it's not used until after the loop.
 define i32 @main() nounwind {
 ; CHECK: entry:
 ; CHECK-NEXT: %result.i = alloca i32, align 4
@@ -27,5 +22,35 @@ while.end:                                        ; preds = %while.cond
   %tmp.i = volatile load i32* %result.i           ; <i32> [#uses=0]
   ret i32 0
 }
-
 declare i32 @bar()
+
+; <rdar://problem/10352360>
+; Indvars shouldn't sink the first alloca between the stacksave and stackrestore
+; intrinsics.
+declare i8* @a(...)
+declare i8* @llvm.stacksave() nounwind
+declare void @llvm.stackrestore(i8*) nounwind
+define void @h(i64 %n) nounwind uwtable ssp {
+; CHECK: entry:
+; CHECK-NEXT: %vla = alloca i8*
+; CHECK-NEXT: %savedstack = call i8* @llvm.stacksave()
+entry:
+  %vla = alloca i8*, i64 %n, align 16
+  %savedstack = call i8* @llvm.stacksave() nounwind
+  %vla.i = alloca i8*, i64 %n, align 16
+  br label %for.body.i
+
+for.body.i:
+  %indvars.iv37.i = phi i64 [ %indvars.iv.next38.i, %for.body.i ], [ 0, %entry ]
+  %call.i = call i8* (...)* @a() nounwind
+  %arrayidx.i = getelementptr inbounds i8** %vla.i, i64 %indvars.iv37.i
+  store i8* %call.i, i8** %arrayidx.i, align 8
+  %indvars.iv.next38.i = add i64 %indvars.iv37.i, 1
+  %exitcond5 = icmp eq i64 %indvars.iv.next38.i, %n
+  br i1 %exitcond5, label %g.exit, label %for.body.i
+
+g.exit:
+  call void @llvm.stackrestore(i8* %savedstack) nounwind
+  %call1 = call i8* (...)* @a(i8** %vla) nounwind
+  ret void
+}