Fix PR6696 and PR6663

When a frame pointer is not otherwise required, and dynamic stack alignment
is necessary solely due to the spilling of a register with larger alignment
requirements than the default stack alignment, the frame pointer can be both
used as a general purpose register and a frame pointer. That goes poorly, for
obvious reasons. This patch brings back a bit of old logic for identifying
the use of such registers and conservatively reserves the frame pointer
during register allocation in such cases.

For now, implement for X86 only since it's 32-bit linux which is hitting this,
and we want a targeted fix for 2.7. As a follow-on, this will be expanded
to handle other targets, as theoretically the problem could arise elsewhere
as well.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@100559 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 25 insertions, 13 deletions

diff --git a/lib/Target/X86/X86RegisterInfo.td b/lib/Target/X86/X86RegisterInfo.td
index 76b8f7a953..49a6ca0928 100644
--- a/lib/Target/X86/X86RegisterInfo.td
+++ b/lib/Target/X86/X86RegisterInfo.td
@@ -352,11 +352,12 @@ def GR8 : RegisterClass<"X86", [i8],  8,
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
       const X86Subtarget &Subtarget = TM.getSubtarget<X86Subtarget>();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       // Does the function dedicate RBP / EBP to being a frame ptr?
       if (!Subtarget.is64Bit())
         // In 32-mode, none of the 8-bit registers aliases EBP or ESP.
         return begin() + 8;
-      else if (RI->hasFP(MF))
+      else if (RI->hasFP(MF) || MFI->getReserveFP())
         // If so, don't allocate SPL or BPL.
         return array_endof(X86_GR8_AO_64) - 1;
       else
@@ -396,9 +397,10 @@ def GR16 : RegisterClass<"X86", [i16], 16,
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
       const X86Subtarget &Subtarget = TM.getSubtarget<X86Subtarget>();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       if (Subtarget.is64Bit()) {
         // Does the function dedicate RBP to being a frame ptr?
-        if (RI->hasFP(MF))
+        if (RI->hasFP(MF) || MFI->getReserveFP())
           // If so, don't allocate SP or BP.
           return array_endof(X86_GR16_AO_64) - 1;
         else
@@ -406,7 +408,7 @@ def GR16 : RegisterClass<"X86", [i16], 16,
           return array_endof(X86_GR16_AO_64);
       } else {
         // Does the function dedicate EBP to being a frame ptr?
-        if (RI->hasFP(MF))
+        if (RI->hasFP(MF) || MFI->getReserveFP())
           // If so, don't allocate SP or BP.
           return begin() + 6;
         else
@@ -447,9 +449,10 @@ def GR32 : RegisterClass<"X86", [i32], 32,
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
       const X86Subtarget &Subtarget = TM.getSubtarget<X86Subtarget>();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       if (Subtarget.is64Bit()) {
         // Does the function dedicate RBP to being a frame ptr?
-        if (RI->hasFP(MF))
+        if (RI->hasFP(MF) || MFI->getReserveFP())
           // If so, don't allocate ESP or EBP.
           return array_endof(X86_GR32_AO_64) - 1;
         else
@@ -457,7 +460,7 @@ def GR32 : RegisterClass<"X86", [i32], 32,
           return array_endof(X86_GR32_AO_64);
       } else {
         // Does the function dedicate EBP to being a frame ptr?
-        if (RI->hasFP(MF))
+        if (RI->hasFP(MF) || MFI->getReserveFP())
           // If so, don't allocate ESP or EBP.
           return begin() + 6;
         else
@@ -484,9 +487,11 @@ def GR64 : RegisterClass<"X86", [i64], 64,
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
       const X86Subtarget &Subtarget = TM.getSubtarget<X86Subtarget>();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       if (!Subtarget.is64Bit())
         return begin();  // None of these are allocatable in 32-bit.
-      if (RI->hasFP(MF)) // Does the function dedicate RBP to being a frame ptr?
+      // Does the function dedicate RBP to being a frame ptr?
+      if (RI->hasFP(MF) || MFI->getReserveFP())
         return end()-3;  // If so, don't allocate RIP, RSP or RBP
       else
         return end()-2;  // If not, just don't allocate RIP or RSP
@@ -589,8 +594,9 @@ def GR16_NOREX : RegisterClass<"X86", [i16], 16,
     GR16_NOREXClass::allocation_order_end(const MachineFunction &MF) const {
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       // Does the function dedicate RBP / EBP to being a frame ptr?
-      if (RI->hasFP(MF))
+      if (RI->hasFP(MF) || MFI->getReserveFP())
         // If so, don't allocate SP or BP.
         return end() - 2;
       else
@@ -611,8 +617,9 @@ def GR32_NOREX : RegisterClass<"X86", [i32], 32,
     GR32_NOREXClass::allocation_order_end(const MachineFunction &MF) const {
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       // Does the function dedicate RBP / EBP to being a frame ptr?
-      if (RI->hasFP(MF))
+      if (RI->hasFP(MF) || MFI->getReserveFP())
         // If so, don't allocate ESP or EBP.
         return end() - 2;
       else
@@ -633,8 +640,9 @@ def GR64_NOREX : RegisterClass<"X86", [i64], 64,
     GR64_NOREXClass::allocation_order_end(const MachineFunction &MF) const {
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       // Does the function dedicate RBP to being a frame ptr?
-      if (RI->hasFP(MF))
+      if (RI->hasFP(MF) || MFI->getReserveFP())
         // If so, don't allocate RIP, RSP or RBP.
         return end() - 3;
       else
@@ -675,9 +683,10 @@ def GR32_NOSP : RegisterClass<"X86", [i32], 32,
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
       const X86Subtarget &Subtarget = TM.getSubtarget<X86Subtarget>();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       if (Subtarget.is64Bit()) {
         // Does the function dedicate RBP to being a frame ptr?
-        if (RI->hasFP(MF))
+        if (RI->hasFP(MF) || MFI->getReserveFP())
           // If so, don't allocate EBP.
           return array_endof(X86_GR32_NOSP_AO_64) - 1;
         else
@@ -685,7 +694,7 @@ def GR32_NOSP : RegisterClass<"X86", [i32], 32,
           return array_endof(X86_GR32_NOSP_AO_64);
       } else {
         // Does the function dedicate EBP to being a frame ptr?
-        if (RI->hasFP(MF))
+        if (RI->hasFP(MF) || MFI->getReserveFP())
           // If so, don't allocate EBP.
           return begin() + 6;
         else
@@ -710,9 +719,11 @@ def GR64_NOSP : RegisterClass<"X86", [i64], 64,
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
       const X86Subtarget &Subtarget = TM.getSubtarget<X86Subtarget>();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       if (!Subtarget.is64Bit())
         return begin();  // None of these are allocatable in 32-bit.
-      if (RI->hasFP(MF)) // Does the function dedicate RBP to being a frame ptr?
+      // Does the function dedicate RBP to being a frame ptr?
+      if (RI->hasFP(MF) || MFI->getReserveFP())
         return end()-1;  // If so, don't allocate RBP
       else
         return end();  // If not, any reg in this class is ok.
@@ -733,8 +744,9 @@ def GR64_NOREX_NOSP : RegisterClass<"X86", [i64], 64,
   {
       const TargetMachine &TM = MF.getTarget();
       const TargetRegisterInfo *RI = TM.getRegisterInfo();
+      const X86MachineFunctionInfo *MFI = MF.getInfo<X86MachineFunctionInfo>();
       // Does the function dedicate RBP to being a frame ptr?
-      if (RI->hasFP(MF))
+      if (RI->hasFP(MF) || MFI->getReserveFP())
         // If so, don't allocate RBP.
         return end() - 1;
       else