lastRegisterUse() should ignore identity copies. Those will be erased.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@48759 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 44 insertions, 7 deletions

diff --git a/lib/CodeGen/SimpleRegisterCoalescing.cpp b/lib/CodeGen/SimpleRegisterCoalescing.cpp
index 6f5b523638..870fcc4408 100644
--- a/lib/CodeGen/SimpleRegisterCoalescing.cpp
+++ b/lib/CodeGen/SimpleRegisterCoalescing.cpp
@@ -1541,6 +1541,10 @@ SimpleRegisterCoalescing::lastRegisterUse(unsigned Start, unsigned End,
            E = mri_->use_end(); I != E; ++I) {
       MachineOperand &Use = I.getOperand();
       MachineInstr *UseMI = Use.getParent();
+      unsigned SrcReg, DstReg;
+      if (tii_->isMoveInstr(*UseMI, SrcReg, DstReg) && SrcReg == DstReg)
+        // Ignore identity copies.
+        continue;
       unsigned Idx = li_->getInstructionIndex(UseMI);
       if (Idx >= Start && Idx < End && Idx >= UseIdx) {
         LastUse = &Use;
@@ -1562,14 +1566,17 @@ SimpleRegisterCoalescing::lastRegisterUse(unsigned Start, unsigned End,
     if (e < s || MI == NULL)
       return NULL;
 
-    for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) {
-      MachineOperand &Use = MI->getOperand(i);
-      if (Use.isRegister() && Use.isUse() && Use.getReg() &&
-          tri_->regsOverlap(Use.getReg(), Reg)) {
-        UseIdx = e;
-        return &Use;
+    // Ignore identity copies.
+    unsigned SrcReg, DstReg;
+    if (!(tii_->isMoveInstr(*MI, SrcReg, DstReg) && SrcReg == DstReg))
+      for (unsigned i = 0, NumOps = MI->getNumOperands(); i != NumOps; ++i) {
+        MachineOperand &Use = MI->getOperand(i);
+        if (Use.isRegister() && Use.isUse() && Use.getReg() &&
+            tri_->regsOverlap(Use.getReg(), Reg)) {
+          UseIdx = e;
+          return &Use;
+        }
       }
-    }
 
     e -= InstrSlots::NUM;
   }
diff --git a/test/CodeGen/PowerPC/2008-03-24-CoalescerBug.ll b/test/CodeGen/PowerPC/2008-03-24-CoalescerBug.ll
new file mode 100644
index 0000000000..67c167aca1
--- /dev/null
+++ b/test/CodeGen/PowerPC/2008-03-24-CoalescerBug.ll
@@ -0,0 +1,30 @@
+; RUN: llvm-as < %s | llc -march=ppc32
+
+	%struct..0objc_object = type { %struct.objc_class* }
+	%struct.NSArray = type { %struct..0objc_object }
+	%struct.NSMutableArray = type { %struct.NSArray }
+	%struct.PFTPersistentSymbols = type { %struct..0objc_object, %struct.VMUSymbolicator*, %struct.NSMutableArray*, %struct.__CFDictionary*, %struct.__CFDictionary*, %struct.__CFDictionary*, %struct.__CFDictionary*, %struct.NSMutableArray*, i8, %struct.pthread_mutex_t, %struct.NSMutableArray*, %struct.pthread_rwlock_t }
+	%struct.VMUMachTaskContainer = type { %struct..0objc_object, i32, i32 }
+	%struct.VMUSymbolicator = type { %struct..0objc_object, %struct.NSMutableArray*, %struct.NSArray*, %struct.NSArray*, %struct.VMUMachTaskContainer*, i8 }
+	%struct.__CFDictionary = type opaque
+	%struct.__builtin_CFString = type { i32*, i32, i8*, i32 }
+	%struct.objc_class = type opaque
+	%struct.objc_selector = type opaque
+	%struct.pthread_mutex_t = type { i32, [40 x i8] }
+	%struct.pthread_rwlock_t = type { i32, [124 x i8] }
+external constant %struct.__builtin_CFString		; <%struct.__builtin_CFString*>:0 [#uses=1]
+
+define void @"-[PFTPersistentSymbols saveSymbolWithName:address:path:lineNumber:flags:owner:]"(%struct.PFTPersistentSymbols* %self, %struct.objc_selector* %_cmd, %struct.NSArray* %name, i64 %address, %struct.NSArray* %path, i32 %lineNumber, i64 %flags, %struct..0objc_object* %owner) nounwind  {
+entry:
+	br i1 false, label %bb12, label %bb21
+bb12:		; preds = %entry
+	%tmp17 = tail call i8 inttoptr (i64 4294901504 to i8 (%struct..0objc_object*, %struct.objc_selector*, %struct.NSArray*)*)( %struct..0objc_object* null, %struct.objc_selector* null, %struct.NSArray* bitcast (%struct.__builtin_CFString* @0 to %struct.NSArray*) ) signext nounwind 		; <i8> [#uses=0]
+	br i1 false, label %bb25, label %bb21
+bb21:		; preds = %bb12, %entry
+	%tmp24 = or i64 %flags, 4		; <i64> [#uses=1]
+	br label %bb25
+bb25:		; preds = %bb21, %bb12
+	%flags_addr.0 = phi i64 [ %tmp24, %bb21 ], [ %flags, %bb12 ]		; <i64> [#uses=1]
+	%tmp3233 = trunc i64 %flags_addr.0 to i32		; <i32> [#uses=0]
+	ret void
+}