[PATCH] D21395: Fix for Bug 28144

[Matthias Braun via llvm-commits]

MatzeB added inline comments.

================
Comment at: lib/CodeGen/RegUsageInfoCollector.cpp:113-126
@@ -112,1 +112,16 @@
 
+  for (MachineBasicBlock &MBB : MF) {
+    for (MachineInstr &MI : MBB) {
+      if (!MI.isCall())
+        continue;
+      for (MachineOperand &MO : MI.operands()) {
+        if (!MO.isRegMask())
+          continue;
+        const uint32_t *CalleeRegMask = MO.getRegMask();
+        for (unsigned i = 0; i < RegMaskSize; ++i)
+          RegMask[i] = RegMask[i] & CalleeRegMask[i];
+        break;
+      }
+    }
+  }
+
----------------
mehdi_amini wrote:
> Matze: I believe the register allocator does not account for register clobbered by callees.
Why do you say so? The registers clobbered by the callees is exactlye what the UsedPhysRegMask in MachineRegisterInfo is about, see also the use of addPhysRegsUsedFromRegMask() in VirtRegMap.cpp/FastRegAlloc.cpp.


http://reviews.llvm.org/D21395