When transforming sext(trunc(load(x))) into sext(smaller load(x)),
the trunc is directly replaced with the smaller load, so don't
try to create a new sext node. This fixes PR4050.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@70179 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index b937eaf..bd4b10e 100644
--- a/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2962,7 +2962,7 @@
if (NarrowLoad.getNode()) {
if (NarrowLoad.getNode() != N0.getNode())
CombineTo(N0.getNode(), NarrowLoad);
- return DAG.getNode(ISD::SIGN_EXTEND, N->getDebugLoc(), VT, NarrowLoad);
+ return SDValue(N, 0); // Return N so it doesn't get rechecked!
}
// See if the value being truncated is already sign extended. If so, just
diff --git a/test/CodeGen/X86/fold-sext-trunc.ll b/test/CodeGen/X86/fold-sext-trunc.ll
new file mode 100644
index 0000000..1016b10
--- /dev/null
+++ b/test/CodeGen/X86/fold-sext-trunc.ll
@@ -0,0 +1,20 @@
+; RUN: llvm-as < %s | llc -march=x86-64 | grep movslq | count 1
+; PR4050
+
+ type { i64 } ; type %0
+ %struct.S1 = type { i16, i32 }
+@g_10 = external global %struct.S1 ; <%struct.S1*> [#uses=2]
+
+declare void @func_28(i64, i64)
+
+define void @int322(i32 %foo) nounwind {
+entry:
+ %val = load i64* getelementptr (%0* bitcast (%struct.S1* @g_10 to %0*), i32 0, i32 0) ; <i64> [#uses=1]
+ %0 = load i32* getelementptr (%struct.S1* @g_10, i32 0, i32 1), align 4 ; <i32> [#uses=1]
+ %1 = sext i32 %0 to i64 ; <i64> [#uses=1]
+ %tmp4.i = lshr i64 %val, 32 ; <i64> [#uses=1]
+ %tmp5.i = trunc i64 %tmp4.i to i32 ; <i32> [#uses=1]
+ %2 = sext i32 %tmp5.i to i64 ; <i64> [#uses=1]
+ tail call void @func_28(i64 %2, i64 %1) nounwind
+ ret void
+}