fix a subtle volatile handling bug.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50428 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 42 insertions, 7 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index c707e6e..86aca07 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9432,16 +9432,21 @@ Instruction *InstCombiner::FoldPHIArgOpIntoPHI(PHINode &PN) {
   // Insert and return the new operation.
   if (CastInst* FirstCI = dyn_cast<CastInst>(FirstInst))
     return CastInst::create(FirstCI->getOpcode(), PhiVal, PN.getType());
-  else if (isa<LoadInst>(FirstInst))
-    return new LoadInst(PhiVal, "", isVolatile);
-  else if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
+  if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(FirstInst))
     return BinaryOperator::create(BinOp->getOpcode(), PhiVal, ConstantOp);
-  else if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
+  if (CmpInst *CIOp = dyn_cast<CmpInst>(FirstInst))
     return CmpInst::create(CIOp->getOpcode(), CIOp->getPredicate(), 
                            PhiVal, ConstantOp);
-  else
-    assert(0 && "Unknown operation");
-  return 0;
+  assert(isa<LoadInst>(FirstInst) && "Unknown operation");
+  
+  // If this was a volatile load that we are merging, make sure to loop through
+  // and mark all the input loads as non-volatile.  If we don't do this, we will
+  // insert a new volatile load and the old ones will not be deletable.
+  if (isVolatile)
+    for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
+      cast<LoadInst>(PN.getIncomingValue(i))->setVolatile(false);
+  
+  return new LoadInst(PhiVal, "", isVolatile);
 }
 
 /// DeadPHICycle - Return true if this PHI node is only used by a PHI node cycle
diff --git a/test/Transforms/InstCombine/2008-04-29-VolatileLoadMerge.ll b/test/Transforms/InstCombine/2008-04-29-VolatileLoadMerge.ll
new file mode 100644
index 0000000..9f378cc
--- /dev/null
+++ b/test/Transforms/InstCombine/2008-04-29-VolatileLoadMerge.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {volatile load} | count 1
+; PR2262
+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-darwin8"
+@g_1 = internal global i32 0		; <i32*> [#uses=3]
+@.str = internal constant [13 x i8] c"checksum = 0\00"		; <[13 x i8]*> [#uses=1]
+@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  {
+entry:
+	%tmp93 = icmp slt i32 0, 10		; <i1> [#uses=0]
+	%tmp34 = volatile load i32* @g_1, align 4		; <i32> [#uses=1]
+	br label %bb
+
+bb:		; preds = %bb, %entry
+	%b.0.reg2mem.0 = phi i32 [ 0, %entry ], [ %tmp6, %bb ]		; <i32> [#uses=1]
+	%tmp3.reg2mem.0 = phi i32 [ %tmp34, %entry ], [ %tmp3, %bb ]		; <i32> [#uses=1]
+	%tmp4 = add i32 %tmp3.reg2mem.0, 5		; <i32> [#uses=1]
+	volatile store i32 %tmp4, i32* @g_1, align 4
+	%tmp6 = add i32 %b.0.reg2mem.0, 1		; <i32> [#uses=2]
+	%tmp9 = icmp slt i32 %tmp6, 10		; <i1> [#uses=1]
+	%tmp3 = volatile load i32* @g_1, align 4		; <i32> [#uses=1]
+	br i1 %tmp9, label %bb, label %bb11
+
+bb11:		; preds = %bb
+	%tmp14 = call i32 @puts( i8* getelementptr ([13 x i8]* @.str, i32 0, i32 0) ) nounwind 		; <i32> [#uses=0]
+	ret i32 0
+}
+
+declare i32 @puts(i8*)