From: Jakob Stoklund Olesen <stoklund@2pi.dk>
Date: Mon, 17 May 2010 02:49:18 +0000 (+0000)
Subject: Now that we don't keep live registers across calls, there is not reason to go
X-Git-Url: http://plrg.eecs.uci.edu/git/?a=commitdiff_plain;h=4b6bbe885d851b1cfba2be9b5efc6365a2b7828a;p=oota-llvm.git

Now that we don't keep live registers across calls, there is not reason to go
through the very long list of call-clobbered registers. We just assume all
registers are clobbered.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103930 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/RegAllocFast.cpp b/lib/CodeGen/RegAllocFast.cpp
index 060ee770abe..484b36580a0 100644
--- a/lib/CodeGen/RegAllocFast.cpp
+++ b/lib/CodeGen/RegAllocFast.cpp
@@ -736,9 +736,20 @@ void RAFast::AllocateBasicBlock() {
         UsedInInstr.set(Alias);
     }
 
+    unsigned DefOpEnd = MI->getNumOperands();
+    if (TID.isCall()) {
+      // Spill all virtregs before a call. This serves two purposes: 1. If an
+      // exception is thrown, the landing pad is going to expect to find registers
+      // in their spill slots, and 2. we don't have to wade through all the
+      // <imp-def> operands on the call instruction.
+      DefOpEnd = VirtOpEnd;
+      DEBUG(dbgs() << "  Spilling remaining registers before call.\n");
+      spillAll(MI);
+    }
+
     // Third scan.
     // Allocate defs and collect dead defs.
-    for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+    for (unsigned i = 0; i != DefOpEnd; ++i) {
       MachineOperand &MO = MI->getOperand(i);
       if (!MO.isReg() || !MO.isDef() || !MO.getReg()) continue;
       unsigned Reg = MO.getReg();
@@ -758,12 +769,6 @@ void RAFast::AllocateBasicBlock() {
       setPhysReg(MO, PhysReg);
     }
 
-    // Spill all dirty virtregs before a call, in case of an exception.
-    if (TID.isCall()) {
-      DEBUG(dbgs() << "  Spilling remaining registers before call.\n");
-      spillAll(MI);
-    }
-
     // Process virtreg deads.
     for (unsigned i = 0, e = VirtKills.size(); i != e; ++i)
       killVirtReg(VirtKills[i]);