Minor optimization. sign-ext/anyext of undef is still undef.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127598 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index 8deaae935a6094f52ec68cd1dbdf1927ea43eace..2c97d35618d9aa43ce6810b73f2282f8f509875b 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -2482,6 +2482,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL,
            "Vector element count mismatch!");
     if (OpOpcode == ISD::SIGN_EXTEND || OpOpcode == ISD::ZERO_EXTEND)
       return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0));
+    else if (OpOpcode == ISD::UNDEF)
+      return getUNDEF(VT);
     break;
   case ISD::ZERO_EXTEND:
     assert(VT.isInteger() && Operand.getValueType().isInteger() &&
@@ -2512,6 +2514,8 @@ SDValue SelectionDAG::getNode(unsigned Opcode, DebugLoc DL,
         OpOpcode == ISD::ANY_EXTEND)
       // (ext (zext x)) -> (zext x)  and  (ext (sext x)) -> (sext x)
       return getNode(OpOpcode, DL, VT, Operand.getNode()->getOperand(0));
+    else if (OpOpcode == ISD::UNDEF)
+      return getUNDEF(VT);
 
     // (ext (trunx x)) -> x
     if (OpOpcode == ISD::TRUNCATE) {

diff --git a/test/CodeGen/ARM/shifter_operand.ll b/test/CodeGen/ARM/shifter_operand.ll
index 01e3a922f65681cd0fa8f2612023c4d5b74282d3..be891bc76d3accea49d6b00250d87aeb6ffd1114 100644 (file)
--- a/test/CodeGen/ARM/shifter_operand.ll
+++ b/test/CodeGen/ARM/shifter_operand.ll
@@ -51,19 +51,19 @@ entry:
 
 declare i8* @malloc(...)
 
-define fastcc void @test4() nounwind {
+define fastcc void @test4(i16 %addr) nounwind {
 entry:
 ; A8: test4:
-; A8: ldr r1, [r0, r0, lsl #2]
-; A8: str r1, [r0, r0, lsl #2]
+; A8: ldr r2, [r0, r1, lsl #2]
+; A8: str r2, [r0, r1, lsl #2]
 
 ; A9: test4:
-; A9: add r0, r0, r0, lsl #2
+; A9: add r0, r0, r4, lsl #2
 ; A9: ldr r1, [r0]
 ; A9: str r1, [r0]
   %0 = tail call i8* (...)* @malloc(i32 undef) nounwind
   %1 = bitcast i8* %0 to i32*
-  %2 = sext i16 undef to i32
+  %2 = sext i16 %addr to i32
   %3 = getelementptr inbounds i32* %1, i32 %2
   %4 = load i32* %3, align 4
   %5 = add nsw i32 %4, 1

diff --git a/test/CodeGen/ARM/undef-sext.ll b/test/CodeGen/ARM/undef-sext.ll
new file mode 100644 (file)
index 0000000..2c28da3
--- /dev/null
+++ b/test/CodeGen/ARM/undef-sext.ll
@@ -0,0 +1,14 @@
+; RUN: llc < %s -mtriple=armv7-apple-darwin -mcpu=cortex-a8 | FileCheck %s
+
+; No need to sign-extend undef.
+
+define i32 @t(i32* %a) nounwind {
+entry:
+; CHECK: t:
+; CHECK: ldr r0, [r0]
+; CHECK: bx lr
+  %0 = sext i16 undef to i32
+  %1 = getelementptr inbounds i32* %a, i32 %0
+  %2 = load i32* %1, align 4
+  ret i32 %2
+}