Do not issue identity copies.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52373 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LowerSubregs.cpp b/lib/CodeGen/LowerSubregs.cpp
index 0710a35..296e6d4 100644
--- a/lib/CodeGen/LowerSubregs.cpp
+++ b/lib/CodeGen/LowerSubregs.cpp
@@ -108,15 +108,20 @@
DOUT << "subreg: CONVERTING: " << *MI;
- // Insert sub-register copy
- const TargetRegisterClass *TRC0 = TRI.getPhysicalRegisterRegClass(DstSubReg);
- const TargetRegisterClass *TRC1 = TRI.getPhysicalRegisterRegClass(InsReg);
- TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
+ if (DstSubReg == InsReg) {
+ // No need to insert an identify copy instruction.
+ DOUT << "subreg: eliminated!";
+ } else {
+ // Insert sub-register copy
+ const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
+ const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
+ TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
+ MachineBasicBlock::iterator dMI = MI;
+ DOUT << "subreg: " << *(--dMI);
#endif
+ }
DOUT << "\n";
MBB->remove(MI);
@@ -149,15 +154,19 @@
DOUT << "subreg: CONVERTING: " << *MI;
- // Insert sub-register copy
- const TargetRegisterClass *TRC0 = TRI.getPhysicalRegisterRegClass(DstSubReg);
- const TargetRegisterClass *TRC1 = TRI.getPhysicalRegisterRegClass(InsReg);
- TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
-
+ if (DstSubReg == InsReg) {
+ // No need to insert an identify copy instruction.
+ DOUT << "subreg: eliminated!";
+ } else {
+ // Insert sub-register copy
+ const TargetRegisterClass *TRC0= TRI.getPhysicalRegisterRegClass(DstSubReg);
+ const TargetRegisterClass *TRC1= TRI.getPhysicalRegisterRegClass(InsReg);
+ TII.copyRegToReg(*MBB, MI, DstSubReg, InsReg, TRC0, TRC1);
#ifndef NDEBUG
- MachineBasicBlock::iterator dMI = MI;
- DOUT << "subreg: " << *(--dMI);
+ MachineBasicBlock::iterator dMI = MI;
+ DOUT << "subreg: " << *(--dMI);
#endif
+ }
DOUT << "\n";
MBB->remove(MI);
diff --git a/test/CodeGen/X86/2008-06-16-SubregsBug.ll b/test/CodeGen/X86/2008-06-16-SubregsBug.ll
new file mode 100644
index 0000000..75513b6
--- /dev/null
+++ b/test/CodeGen/X86/2008-06-16-SubregsBug.ll
@@ -0,0 +1,14 @@
+; RUN: llvm-as < %s | llc -mtriple=i386-apple-darwin | grep mov | count 4
+
+define i16 @test(i16* %tmp179) nounwind {
+ %tmp180 = load i16* %tmp179, align 2 ; <i16> [#uses=2]
+ %tmp184 = and i16 %tmp180, -1024 ; <i16> [#uses=1]
+ %tmp186 = icmp eq i16 %tmp184, -32768 ; <i1> [#uses=1]
+ br i1 %tmp186, label %bb189, label %bb288
+
+bb189: ; preds = %0
+ ret i16 %tmp180
+
+bb288: ; preds = %0
+ ret i16 32
+}