From: Anton Korobeynikov <asl@math.spbu.ru>
Date: Sun, 26 Aug 2007 21:43:30 +0000 (+0000)
Subject: Don't promote volatile loads/stores. This is needed (for example) to handle setjmp... 
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=9f528e628090ee0ffca35d4577c23b6544f9a119;p=oota-llvm.git

Don't promote volatile loads/stores. This is needed (for example) to handle setjmp/longjmp properly.
This fixes PR1520.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@41461 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
index a6fb8707d41..33489711388 100644
--- a/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
+++ b/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
@@ -63,14 +63,17 @@ bool llvm::isAllocaPromotable(const AllocaInst *AI) {
   // FIXME: If the memory unit is of pointer or integer type, we can permit
   // assignments to subsections of the memory unit.
 
-  // Only allow direct loads and stores...
+  // Only allow direct and non-volatile loads and stores...
   for (Value::use_const_iterator UI = AI->use_begin(), UE = AI->use_end();
        UI != UE; ++UI)     // Loop over all of the uses of the alloca
-    if (isa<LoadInst>(*UI)) {
-      // noop
+    if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+      if (LI->isVolatile())
+        return false;
     } else if (const StoreInst *SI = dyn_cast<StoreInst>(*UI)) {
       if (SI->getOperand(0) == AI)
         return false;   // Don't allow a store OF the AI, only INTO the AI.
+      if (SI->isVolatile())
+        return false;
     } else {
       return false;   // Not a load or store.
     }
diff --git a/test/Transforms/Mem2Reg/2007-08-27-VolatileLoadsStores.ll b/test/Transforms/Mem2Reg/2007-08-27-VolatileLoadsStores.ll
new file mode 100644
index 00000000000..579ed41c94c
--- /dev/null
+++ b/test/Transforms/Mem2Reg/2007-08-27-VolatileLoadsStores.ll
@@ -0,0 +1,47 @@
+; RUN: llvm-as < %s | opt -std-compile-opts | llvm-dis | grep volatile | count 3
+; PR1520
+; Don't promote volatile loads/stores. This is really needed to handle setjmp/lonjmp properly.
+
+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 = "i686-pc-linux-gnu"
+	%struct.__jmp_buf_tag = type { [6 x i32], i32, %struct.__sigset_t }
+	%struct.__sigset_t = type { [32 x i32] }
+@j = external global [1 x %struct.__jmp_buf_tag]		; <[1 x %struct.__jmp_buf_tag]*> [#uses=1]
+
+define i32 @f() {
+entry:
+	%retval = alloca i32, align 4		; <i32*> [#uses=2]
+	%v = alloca i32, align 4		; <i32*> [#uses=3]
+	%tmp = alloca i32, align 4		; <i32*> [#uses=3]
+	%"alloca point" = bitcast i32 0 to i32		; <i32> [#uses=0]
+	volatile store i32 0, i32* %v, align 4
+	%tmp1 = call i32 @_setjmp( %struct.__jmp_buf_tag* getelementptr ([1 x %struct.__jmp_buf_tag]* @j, i32 0, i32 0) )		; <i32> [#uses=1]
+	%tmp2 = icmp ne i32 %tmp1, 0		; <i1> [#uses=1]
+	%tmp23 = zext i1 %tmp2 to i8		; <i8> [#uses=1]
+	%toBool = icmp ne i8 %tmp23, 0		; <i1> [#uses=1]
+	br i1 %toBool, label %bb, label %bb5
+
+bb:		; preds = %entry
+	%tmp4 = volatile load i32* %v, align 4		; <i32> [#uses=1]
+	store i32 %tmp4, i32* %tmp, align 4
+	br label %bb6
+
+bb5:		; preds = %entry
+	volatile store i32 1, i32* %v, align 4
+	call void @g( )
+	store i32 0, i32* %tmp, align 4
+	br label %bb6
+
+bb6:		; preds = %bb5, %bb
+	%tmp7 = load i32* %tmp, align 4		; <i32> [#uses=1]
+	store i32 %tmp7, i32* %retval, align 4
+	br label %return
+
+return:		; preds = %bb6
+	%retval8 = load i32* %retval		; <i32> [#uses=1]
+	ret i32 %retval8
+}
+
+declare i32 @_setjmp(%struct.__jmp_buf_tag*)
+
+declare void @g()