Use TII->findCommutedOpIndices to find the commute operands (rather than guessing).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@76472 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/TwoAddressInstructionPass.cpp

@@ -879,10 +879,14 @@ bool TwoAddressInstructionPass::runOnMachineFunction(MachineFunction &MF) {
             // so, swap the B and C operands.  This makes the live ranges of A
             // and C joinable.
             // FIXME: This code also works for A := B op C instructions.
-            if (TID.isCommutable() && mi->getNumOperands() >= 3) {
-              assert(mi->getOperand(3-si).isReg() &&
-                     "Not a proper commutative instruction!");
-              unsigned regC = mi->getOperand(3-si).getReg();
+            unsigned SrcOp1, SrcOp2;
+            if (TID.isCommutable() && mi->getNumOperands() >= 3 &&
+                TII->findCommutedOpIndices(mi, SrcOp1, SrcOp2)) {
+              unsigned regC = 0;
+              if (si == SrcOp1)
+                regC = mi->getOperand(SrcOp2).getReg();
+              else if (si == SrcOp2)
+                regC = mi->getOperand(SrcOp1).getReg();
               if (isKilled(*mi, regC, MRI, TII)) {
                 if (CommuteInstruction(mi, mbbi, regB, regC, Dist)) {
                   ++NumCommuted;

test/CodeGen/Thumb/2009-07-20-TwoAddrBug.ll

@@ -0,0 +1,11 @@
+; RUN: llvm-as < %s | llc -mtriple=thumbv6-apple-darwin10
+
+@Time.2535 = external global i64		; <i64*> [#uses=2]
+
+define arm_apcscc i64 @millisecs() nounwind {
+entry:
+	%0 = load i64* @Time.2535, align 4		; <i64> [#uses=2]
+	%1 = add i64 %0, 1		; <i64> [#uses=1]
+	store i64 %1, i64* @Time.2535, align 4
+	ret i64 %0
+}