ARM: When re-creating a branch via InsertBranch, preserve CPSR flags.

In particular, this preserves the kill flag, which allows the Thumb2 cbn?z
optimization to be applied in cases where a branch has been re-created after
the live variables analysis pass, e.g. by the machine block placement pass.

This appears to be low risk; a number of other targets seem to already be
doing something similar, e.g. AArch64, PowerPC.

Differential Revision: http://reviews.llvm.org/D9184

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235639 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Target/ARM/ARMBaseInstrInfo.cpp b/lib/Target/ARM/ARMBaseInstrInfo.cpp
index 93742dd6c725edfb95dde9aade8c77339b522548..a370ab376754cff65c19336c808086d20a49c671 100644 (file)
--- a/lib/Target/ARM/ARMBaseInstrInfo.cpp
+++ b/lib/Target/ARM/ARMBaseInstrInfo.cpp
@@ -410,6 +410,8 @@ ARMBaseInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
   assert((Cond.size() == 2 || Cond.size() == 0) &&
          "ARM branch conditions have two components!");
 
+  // For conditional branches, we use addOperand to preserve CPSR flags.
+
   if (!FBB) {
     if (Cond.empty()) { // Unconditional branch?
       if (isThumb)
@@ -418,13 +420,13 @@ ARMBaseInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB,
         BuildMI(&MBB, DL, get(BOpc)).addMBB(TBB);
     } else
       BuildMI(&MBB, DL, get(BccOpc)).addMBB(TBB)
-        .addImm(Cond[0].getImm()).addReg(Cond[1].getReg());
+        .addImm(Cond[0].getImm()).addOperand(Cond[1]);
     return 1;
   }
 
   // Two-way conditional branch.
   BuildMI(&MBB, DL, get(BccOpc)).addMBB(TBB)
-    .addImm(Cond[0].getImm()).addReg(Cond[1].getReg());
+    .addImm(Cond[0].getImm()).addOperand(Cond[1]);
   if (isThumb)
     BuildMI(&MBB, DL, get(BOpc)).addMBB(FBB).addImm(ARMCC::AL).addReg(0);
   else

diff --git a/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll b/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll
index dd0a0a0803d164d699342e9d0683c495d8059efb..f85203e381b9cbcf500f141da0f1111a9ef55d03 100644 (file)
--- a/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll
+++ b/test/CodeGen/ARM/sjlj-prepare-critical-edge.ll
@@ -79,7 +79,7 @@ declare void @terminatev()
 ; CHECK: str r0, [sp, [[OFFSET:#[0-9]+]]]
 ; CHECK: ldr [[R0:r[0-9]+]], [sp, [[OFFSET]]]
 ; CHECK: {{.*}}@ %do.body.i.i.i
-; CHECK: cmp [[R0]], #0
+; CHECK: cbz [[R0]]
 
 %"class.std::__1::basic_string" = type { %"class.std::__1::__compressed_pair" }
 %"class.std::__1::__compressed_pair" = type { %"class.std::__1::__libcpp_compressed_pair_imp" }

diff --git a/test/CodeGen/Thumb2/v8_IT_5.ll b/test/CodeGen/Thumb2/v8_IT_5.ll
index 2da75ad2143679aeacef72e0fa1675cee535ad8f..78b80d7dcdefa849c3c56631096120dd47f2725b 100644 (file)
--- a/test/CodeGen/Thumb2/v8_IT_5.ll
+++ b/test/CodeGen/Thumb2/v8_IT_5.ll
@@ -3,8 +3,7 @@
 ; CHECK: it    ne
 ; CHECK-NEXT: cmpne
 ; CHECK-NEXT: bne [[JUMPTARGET:.LBB[0-9]+_[0-9]+]]
-; CHECK: cmp
-; CHECK-NEXT: beq
+; CHECK: cbz
 ; CHECK-NEXT: %if.else163
 ; CHECK-NEXT: mov.w
 ; CHECK-NEXT: b