If a register is both an early clobber and part of a tied use, handle the use

before the clobber so that we copy the value if needed.

Fixes pr11415.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145056 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index 7ac38598c3aee78d6eb280bbc3549eb3f2564c05..4664a3c4299f5ef69ba460e21eac0b9944b5f9c2 100644 (file)
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -682,7 +682,7 @@ void RAFast::handleThroughOperands(MachineInstr *MI,
   }
 
   SmallVector<unsigned, 8> PartialDefs;
-  DEBUG(dbgs() << "Allocating tied uses and early clobbers.\n");
+  DEBUG(dbgs() << "Allocating tied uses.\n");
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
     MachineOperand &MO = MI->getOperand(i);
     if (!MO.isReg()) continue;
@@ -704,15 +704,24 @@ void RAFast::handleThroughOperands(MachineInstr *MI,
       // That would confuse the later phys-def processing pass.
       LiveRegMap::iterator LRI = reloadVirtReg(MI, i, Reg, 0);
       PartialDefs.push_back(LRI->second.PhysReg);
-    } else if (MO.isEarlyClobber()) {
-      // Note: defineVirtReg may invalidate MO.
-      LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, 0);
-      unsigned PhysReg = LRI->second.PhysReg;
-      if (setPhysReg(MI, i, PhysReg))
-        VirtDead.push_back(Reg);
     }
   }
 
+  DEBUG(dbgs() << "Allocating early clobbers.\n");
+  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    MachineOperand &MO = MI->getOperand(i);
+    if (!MO.isReg()) continue;
+    unsigned Reg = MO.getReg();
+    if (!TargetRegisterInfo::isVirtualRegister(Reg)) continue;
+    if (!MO.isEarlyClobber())
+      continue;
+    // Note: defineVirtReg may invalidate MO.
+    LiveRegMap::iterator LRI = defineVirtReg(MI, i, Reg, 0);
+    unsigned PhysReg = LRI->second.PhysReg;
+    if (setPhysReg(MI, i, PhysReg))
+      VirtDead.push_back(Reg);
+  }
+
   // Restore UsedInInstr to a state usable for allocating normal virtual uses.
   UsedInInstr.reset();
   for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {

diff --git a/test/CodeGen/X86/pr11415.ll b/test/CodeGen/X86/pr11415.ll
new file mode 100644 (file)
index 0000000..92c530b
--- /dev/null
+++ b/test/CodeGen/X86/pr11415.ll
@@ -0,0 +1,23 @@
+; RUN: llc %s -o - -regalloc=fast | FileCheck %s
+
+; We used to consider the early clobber in the second asm statement as
+; defining %0 before it was read. This caused us to omit the
+; movq -8(%rsp), %rdx
+
+; CHECK:       #APP
+; CHECK-NEXT:  #NO_APP
+; CHECK-NEXT:  movq    %rcx, %rax
+; CHECK-NEXT:  movq    %rax, -8(%rsp)
+; CHECK-NEXT:  movq    -8(%rsp), %rdx
+; CHECK-NEXT:  #APP
+; CHECK-NEXT:  #NO_APP
+; CHECK-NEXT:  movq    %rdx, %rax
+; CHECK-NEXT:  movq    %rdx, -8(%rsp)
+; CHECK-NEXT:  ret
+
+define i64 @foo() {
+entry:
+  %0 = tail call i64 asm "", "={cx}"() nounwind
+  %1 = tail call i64 asm "", "=&r,0,r,~{rax}"(i64 %0, i64 %0) nounwind
+  ret i64 %1
+}