Thumb2 size reduction fix for tied operands of tMUL.

The tied source operand of tMUL is the second source operand, not the
first like every other two-address thumb instruction. Special case it
in the size reduction pass to make sure we create the tMUL instruction
properly.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151315 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 18 insertions, 6 deletions

diff --git a/lib/Target/ARM/Thumb2SizeReduction.cpp b/lib/Target/ARM/Thumb2SizeReduction.cpp
index 4abff28f02..776d0eff5e 100644
--- a/lib/Target/ARM/Thumb2SizeReduction.cpp
+++ b/lib/Target/ARM/Thumb2SizeReduction.cpp
@@ -597,7 +597,19 @@ Thumb2SizeReduce::ReduceTo2Addr(MachineBasicBlock &MBB, MachineInstr *MI,
 
   unsigned Reg0 = MI->getOperand(0).getReg();
   unsigned Reg1 = MI->getOperand(1).getReg();
-  if (Reg0 != Reg1) {
+  // t2MUL is "special". The tied source operand is second, not first.
+  if (MI->getOpcode() == ARM::t2MUL) {
+    if (Reg0 != MI->getOperand(2).getReg()) {
+      // If the other operand also isn't the same as the destination, we
+      // can't reduce.
+      if (Reg1 != Reg0)
+        return false;
+      // Try to commute the operands to make it a 2-address instruction.
+      MachineInstr *CommutedMI = TII->commuteInstruction(MI);
+      if (!CommutedMI)
+        return false;
+    }
+  } else if (Reg0 != Reg1) {
     // Try to commute the operands to make it a 2-address instruction.
     unsigned CommOpIdx1, CommOpIdx2;
     if (!TII->findCommutedOpIndices(MI, CommOpIdx1, CommOpIdx2) ||
diff --git a/test/CodeGen/ARM/avoid-cpsr-rmw.ll b/test/CodeGen/ARM/avoid-cpsr-rmw.ll
index 877ec18062..1b385ab79c 100644
--- a/test/CodeGen/ARM/avoid-cpsr-rmw.ll
+++ b/test/CodeGen/ARM/avoid-cpsr-rmw.ll
@@ -6,9 +6,9 @@
 define i32 @t1(i32 %a, i32 %b, i32 %c, i32 %d) nounwind readnone {
  entry:
 ; CHECK: t1:
-; CHECK: muls [[REG:(r[0-9]+)]], r2, r3
-; CHECK-NEXT: mul  [[REG2:(r[0-9]+)]], r0, r1
-; CHECK-NEXT: muls r0, [[REG2]], [[REG]]
+; CHECK: muls [[REG:(r[0-9]+)]], r3, r2
+; CHECK-NEXT: mul  [[REG2:(r[0-9]+)]], r1, r0
+; CHECK-NEXT: muls r0, [[REG]], [[REG2]]
   %0 = mul nsw i32 %a, %b
   %1 = mul nsw i32 %c, %d
   %2 = mul nsw i32 %0, %1
diff --git a/test/CodeGen/Thumb2/thumb2-mls.ll b/test/CodeGen/Thumb2/thumb2-mls.ll
index 24c45c53fc..58f9add0fc 100644
--- a/test/CodeGen/Thumb2/thumb2-mls.ll
+++ b/test/CodeGen/Thumb2/thumb2-mls.ll
@@ -15,5 +15,5 @@ define i32 @f2(i32 %a, i32 %b, i32 %c) {
     ret i32 %tmp2
 }
 ; CHECK: f2:
-; CHECK: 	muls	r0, r0, r1
+; CHECK: 	muls	r0, r1, r0
 
diff --git a/test/CodeGen/Thumb2/thumb2-mul.ll b/test/CodeGen/Thumb2/thumb2-mul.ll
index bb97d978cf..ac059bdaf0 100644
--- a/test/CodeGen/Thumb2/thumb2-mul.ll
+++ b/test/CodeGen/Thumb2/thumb2-mul.ll
@@ -2,7 +2,7 @@
 
 define i32 @f1(i32 %a, i32 %b, i32 %c) {
 ; CHECK: f1:
-; CHECK: muls r0, r0, r1
+; CHECK: muls r0, r1, r0
     %tmp = mul i32 %a, %b
     ret i32 %tmp
 }