[ARM] Fix handling of thumb1 out-of-range frame offsets

LocalStackSlotPass assumes that isFrameOffsetLegal doesn't change its
answer when the base register changes. Unfortunately this isn't true
in thumb1, where SP-based loads allow a larger offset than
non-SP-based loads, and this causes the base register reuse code to
generate instructions that are unencodable, causing an assertion
failure. 

Solve this by adding a BaseReg parameter to isFrameOffsetLegal, which
ARMBaseRegisterInfo can then make use of to give the correct answer. 

Differential Revision: http://reviews.llvm.org/D8419

llvm-svn: 232825

6 files changed, 12 insertions, 11 deletions

diff --git a/llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp b/llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp
index 6f5de367f27..33c11fe1fc7 100644
--- a/llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp
+++ b/llvm/lib/Target/AArch64/AArch64RegisterInfo.cpp
@@ -271,7 +271,7 @@ bool AArch64RegisterInfo::needsFrameBaseReg(MachineInstr *MI,
   // The FP is only available if there is no dynamic realignment. We
   // don't know for sure yet whether we'll need that, so we guess based
   // on whether there are any local variables that would trigger it.
-  if (TFI->hasFP(MF) && isFrameOffsetLegal(MI, FPOffset))
+  if (TFI->hasFP(MF) && isFrameOffsetLegal(MI, AArch64::FP, FPOffset))
     return false;
 
   // If we can reference via the stack pointer or base pointer, try that.
@@ -279,7 +279,7 @@ bool AArch64RegisterInfo::needsFrameBaseReg(MachineInstr *MI,
   //        to only disallow SP relative references in the live range of
   //        the VLA(s). In practice, it's unclear how much difference that
   //        would make, but it may be worth doing.
-  if (isFrameOffsetLegal(MI, Offset))
+  if (isFrameOffsetLegal(MI, AArch64::SP, Offset))
     return false;
 
   // The offset likely isn't legal; we want to allocate a virtual base register.
@@ -287,6 +287,7 @@ bool AArch64RegisterInfo::needsFrameBaseReg(MachineInstr *MI,
 }
 
 bool AArch64RegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
+                                             unsigned BaseReg,
                                              int64_t Offset) const {
   assert(Offset <= INT_MAX && "Offset too big to fit in int.");
   assert(MI && "Unable to get the legal offset for nil instruction.");
diff --git a/llvm/lib/Target/AArch64/AArch64RegisterInfo.h b/llvm/lib/Target/AArch64/AArch64RegisterInfo.h
index cb752b36b6a..c01bfa5ea70 100644
--- a/llvm/lib/Target/AArch64/AArch64RegisterInfo.h
+++ b/llvm/lib/Target/AArch64/AArch64RegisterInfo.h
@@ -72,7 +72,7 @@ public:
   bool requiresFrameIndexScavenging(const MachineFunction &MF) const override;
 
   bool needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const override;
-  bool isFrameOffsetLegal(const MachineInstr *MI,
+  bool isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
                           int64_t Offset) const override;
   void materializeFrameBaseRegister(MachineBasicBlock *MBB, unsigned BaseReg,
                                     int FrameIdx,
diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index 49efdc31d78..a8c76573019 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -536,9 +536,8 @@ needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
   // on whether there are any local variables that would trigger it.
   unsigned StackAlign = TFI->getStackAlignment();
   if (TFI->hasFP(MF) && 
-      (MI->getDesc().TSFlags & ARMII::AddrModeMask) != ARMII::AddrModeT1_s &&
       !((MFI->getLocalFrameMaxAlign() > StackAlign) && canRealignStack(MF))) {
-    if (isFrameOffsetLegal(MI, FPOffset))
+    if (isFrameOffsetLegal(MI, getFrameRegister(MF), FPOffset))
       return false;
   }
   // If we can reference via the stack pointer, try that.
@@ -546,7 +545,7 @@ needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
   //        to only disallow SP relative references in the live range of
   //        the VLA(s). In practice, it's unclear how much difference that
   //        would make, but it may be worth doing.
-  if (!MFI->hasVarSizedObjects() && isFrameOffsetLegal(MI, Offset))
+  if (!MFI->hasVarSizedObjects() && isFrameOffsetLegal(MI, ARM::SP, Offset))
     return false;
 
   // The offset likely isn't legal, we want to allocate a virtual base register.
@@ -609,7 +608,7 @@ void ARMBaseRegisterInfo::resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
   (void)Done;
 }
 
-bool ARMBaseRegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
+bool ARMBaseRegisterInfo::isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
                                              int64_t Offset) const {
   const MCInstrDesc &Desc = MI->getDesc();
   unsigned AddrMode = (Desc.TSFlags & ARMII::AddrModeMask);
@@ -653,7 +652,7 @@ bool ARMBaseRegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
     NumBits = 8;
     break;
   case ARMII::AddrModeT1_s:
-    NumBits = 8;
+    NumBits = (BaseReg == ARM::SP ? 8 : 5);
     Scale = 4;
     isSigned = false;
     break;
diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
index af2b9a4c469..fdc1ef9432c 100644
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.h
@@ -143,7 +143,7 @@ public:
                                     int64_t Offset) const override;
   void resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
                          int64_t Offset) const override;
-  bool isFrameOffsetLegal(const MachineInstr *MI,
+  bool isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
                           int64_t Offset) const override;
 
   bool cannotEliminateFrame(const MachineFunction &MF) const;
diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
index b0c3d60ef08..8653734c8c6 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.cpp
@@ -993,7 +993,7 @@ needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
 
   // The frame pointer will point to the end of the stack, so estimate the
   // offset as the difference between the object offset and the FP location.
-  return !isFrameOffsetLegal(MI, Offset);
+  return !isFrameOffsetLegal(MI, getBaseRegister(MF), Offset);
 }
 
 /// Insert defining instruction(s) for BaseReg to
@@ -1045,6 +1045,7 @@ void PPCRegisterInfo::resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
 }
 
 bool PPCRegisterInfo::isFrameOffsetLegal(const MachineInstr *MI,
+                                         unsigned BaseReg,
                                          int64_t Offset) const {
   unsigned FIOperandNum = 0;
   while (!MI->getOperand(FIOperandNum).isFI()) {
diff --git a/llvm/lib/Target/PowerPC/PPCRegisterInfo.h b/llvm/lib/Target/PowerPC/PPCRegisterInfo.h
index 03421745e6f..765d5745628 100644
--- a/llvm/lib/Target/PowerPC/PPCRegisterInfo.h
+++ b/llvm/lib/Target/PowerPC/PPCRegisterInfo.h
@@ -94,7 +94,7 @@ public:
                                     int64_t Offset) const override;
   void resolveFrameIndex(MachineInstr &MI, unsigned BaseReg,
                          int64_t Offset) const override;
-  bool isFrameOffsetLegal(const MachineInstr *MI,
+  bool isFrameOffsetLegal(const MachineInstr *MI, unsigned BaseReg,
                           int64_t Offset) const override;
 
   // Debug information queries.