From: Evan Cheng <evan.cheng@apple.com>
Date: Thu, 12 Feb 2009 10:32:17 +0000 (+0000)
Subject: It's (currently) not safe to keep certain physical registers live across basic blocks... 
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=8679119f4b686d141462bf6d18f4ae0eb0bd0841;p=oota-llvm.git

It's (currently) not safe to keep certain physical registers live across basic blocks, e.g. x86 fp stack registers.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64374 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/VirtRegMap.cpp b/lib/CodeGen/VirtRegMap.cpp
index 95cb0cf5bc1..84c48c652cc 100644
--- a/lib/CodeGen/VirtRegMap.cpp
+++ b/lib/CodeGen/VirtRegMap.cpp
@@ -496,6 +496,12 @@ void AvailableSpills::AddAvailableRegsToLiveIn(MachineBasicBlock &MBB) {
          I = PhysRegsAvailable.begin(), E = PhysRegsAvailable.end();
        I != E; ++I) {
     unsigned Reg = (*I).first;
+    const TargetRegisterClass* RC = TRI->getPhysicalRegisterRegClass(Reg);
+    // FIXME: A temporary workaround. We can't reuse available value if it's
+    // not safe to move the def of the virtual register's class. e.g.
+    // X86::RFP* register classes. Do not add it as a live-in.
+    if (!TII->isSafeToMoveRegClassDefs(RC))
+      continue;
     if (!MBB.isLiveIn(Reg))
       MBB.addLiveIn(Reg);
   }
@@ -1361,7 +1367,12 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
         bool DoReMat = VRM.isReMaterialized(VirtReg);
         int SSorRMId = DoReMat
           ? VRM.getReMatId(VirtReg) : VRM.getStackSlot(VirtReg);
-        unsigned InReg = Spills.getSpillSlotOrReMatPhysReg(SSorRMId);
+        const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
+        // FIXME: A temporary workaround. Don't reuse available value if it's
+        // not safe to move the def of the virtual register's class. e.g.
+        // X86::RFP* register classes.
+        unsigned InReg = TII->isSafeToMoveRegClassDefs(RC) ?
+          Spills.getSpillSlotOrReMatPhysReg(SSorRMId) : 0;
         if (InReg == Phys) {
           // If the value is already available in the expected register, save
           // a reload / remat.
@@ -1387,7 +1398,6 @@ void LocalSpiller::RewriteMBB(MachineBasicBlock &MBB, VirtRegMap &VRM,
 
           // If the reloaded / remat value is available in another register,
           // copy it to the desired register.
-          const TargetRegisterClass* RC = RegInfo->getRegClass(VirtReg);
           TII->copyRegToReg(MBB, &MI, Phys, InReg, RC, RC);
 
           // This invalidates Phys.
diff --git a/test/CodeGen/X86/2009-02-12-SpillerBug.ll b/test/CodeGen/X86/2009-02-12-SpillerBug.ll
new file mode 100644
index 00000000000..49f3ef60059
--- /dev/null
+++ b/test/CodeGen/X86/2009-02-12-SpillerBug.ll
@@ -0,0 +1,28 @@
+; RUN: llvm-as < %s | llc -march=x86 -mtriple=i386-apple-darwin8
+
+define hidden void @__mulxc3({ x86_fp80, x86_fp80 }* noalias nocapture sret %agg.result, x86_fp80 %a, x86_fp80 %b, x86_fp80 %c, x86_fp80 %d) nounwind {
+entry:
+	%0 = mul x86_fp80 %b, %d		; <x86_fp80> [#uses=1]
+	%1 = sub x86_fp80 0xK00000000000000000000, %0		; <x86_fp80> [#uses=1]
+	%2 = add x86_fp80 0xK00000000000000000000, 0xK00000000000000000000		; <x86_fp80> [#uses=1]
+	%3 = fcmp uno x86_fp80 %1, 0xK00000000000000000000		; <i1> [#uses=1]
+	%4 = fcmp uno x86_fp80 %2, 0xK00000000000000000000		; <i1> [#uses=1]
+	%or.cond = and i1 %3, %4		; <i1> [#uses=1]
+	br i1 %or.cond, label %bb47, label %bb71
+
+bb47:		; preds = %entry
+	%5 = fcmp uno x86_fp80 %a, 0xK00000000000000000000		; <i1> [#uses=1]
+	br i1 %5, label %bb60, label %bb62
+
+bb60:		; preds = %bb47
+	%6 = tail call x86_fp80 @copysignl(x86_fp80 0xK00000000000000000000, x86_fp80 %a) nounwind readnone		; <x86_fp80> [#uses=0]
+	br label %bb62
+
+bb62:		; preds = %bb60, %bb47
+	unreachable
+
+bb71:		; preds = %entry
+	ret void
+}
+
+declare x86_fp80 @copysignl(x86_fp80, x86_fp80) nounwind readnone